Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A study of certain phenological factors as they influence growth in the apple, malus pumila, (mill.) Beingessner, Henry Francis 1954

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1954_A4 B3 S8.pdf [ 6.26MB ]
Metadata
JSON: 831-1.0106298.json
JSON-LD: 831-1.0106298-ld.json
RDF/XML (Pretty): 831-1.0106298-rdf.xml
RDF/JSON: 831-1.0106298-rdf.json
Turtle: 831-1.0106298-turtle.txt
N-Triples: 831-1.0106298-rdf-ntriples.txt
Original Record: 831-1.0106298-source.json
Full Text
831-1.0106298-fulltext.txt
Citation
831-1.0106298.ris

Full Text

A STUDY OF CERTAIN PHENOLOGICAL FACTORS AS THEY INFLUENCE GROWTH IN THE APPLE, Malua pumila. (MILL.) by HENRY FRANCIS BEINGESSNER A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN AGRICULTURE in the Department of Horticulture We accept t h i s thesis as conforming t o the standard required from candidates f o r the degree of MASTER OF SCIENCE IN AGRICULTURE Members of the Department of Horticulture THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1954 A STUDY OF CERTAIN PHENOLOGICAL FACTORS AS THEY INFLUENCE GROWTH IN THE APPLE, Malus pumila. (MILL.) Abstract The investigation i s a study of the science of phenology i n r e l a t i o n to the maturation of the f r u i t of the apple, Malus pumila. ( M i l l . ) through the medium of the Heat Unit Theory, which i s an expression of the cli m a t o l o g i c a l factor of temperature and more p a r t i c u l a r l y average temperature. The study may be divided into three parts, the f i r s t of which introduces the problem of v a r i a b i l i t y i n t o t a l degree days (the basic unit employed i n the Heat Unit Theory] between v a r i e t i e s of apple and between years. A -maturity c l a s s i f i c a t i o n i s established based on t o t a l degree days for several v a r i e t i e s grown at the Central Experimental Farm, Ottawa, Ontario. The second part examines the three basic d i f f i c u l t i e s encountered in the establishment of a phonological period, namely, when t o begin the period, what base or unit temperature below which the apple i s assumed not to grow and when to end the period. It was found that starting the phonological period ten days before f u l l bloom gave better precision than when the period was started at f u l l bloom. No one base temperature or combination of 2. temperatures appeared to be entirely satisfactory although the base temperature of *f2°F. occupied a medial position. The adoption of the ordinary date of harvest as obtained from f i e l d records proved to be as reliable as the index of maturity established by research. Temperature statistics other than the average, such as minimum and night temperatures, used i n the x calculation of heat units did not improve the precision of a prediction. An accumulation of temperature range appeared superior to accumulation of temperature st a t i s t i c s based on the Heat Unit Theory. No relationship -was found to exist between accumulation of sunshine and solar radiation units and the length of the phonological period. In the third part of the investigation the value of total degree days as well as that of various base temperatures i s determined for a relatively long period of time at two Experimental Stations, one at Summerland, Bri t i s h Columbia, and the other at Ottawa, Ontario. Actual measurements of the rate of enlargement of an apple are correlated with\verage temperature for the same period. Ho increases i n precision were noted with the extension of the time interval under study, nor were the correlations obtained indicative of a good relationship between growth of an apple and average temperature. 3* The number of days i n the phonological period proved to be as good f o r prediction purposes as any of the methods used i n the i n v e s t i g a t i o n , p a r t i c u l a r l y f o r the c l i m a t o l o g i c a l environment experienced at Summerland. Acknowledgement The author wishes to acknowledge the assistance given him by Dr. A. F. Barss, Chairman of the Department of Horticulture; and would thank Dr. G. H. Harris, Professor of Horticulture, without whose guidance, moral support, h e l p f u l c r i t i c i s m and suggestions, t h i s study could not have been culminated. He also wishes to thank Mr. M. B. Davis, Chief, D i v i s i o n of Horticulture, Central Experimental Farm, Ottawa, who so generously granted permission to use data co l l e c t e d at the Divisi o n in t h i s investigation. Thanks are due to the other members of Mr. Davis' s t a f f , and to Mr. G. W. Robertson of the Divis i o n of F i e l d Husbandry for the many excellent suggestions they have offered throughout the course of the study. Grateful appreciation i s extended t o Dr. T. H. Anstey and Mr. A. J. Mann of the Experimental Station, Summerland, f o r t h e i r information on phenological data gathered at that Station. Table of Contents Page Introduction* • • • • 1 Review of Literature•••••••••••••••••••• 6 Materials and Methods*••••••••••••• ...... 30 Part I 31 Part II 32 Part I I I . . . . . . . . . . . 36 Results of the Investigation kO Part I.. ... hO Part I I . . Part I I I . . . . . . . . . 60 D i s c u s s i o n * • . • • 83 Summary••••••••••• 107 C o n c l u s i o n . • • • • • • • • • * . . . . . . . I l l Li t e r a t u r e Cited llh Twenty-nine tables and f i v e graphs A STUDY OF CERTAIN PHENOLOGICAL FACTORS AS THEY INFLUENCE GROWTH IN THE APPLE, Malus pumila. (MILL.) It has been said that energy rules the universe. On Earth i t i s the delicate balance of temperature and l i g h t supplied by the sun which activates the photosynthetic and chemical processes so necessary f o r the i n i t i a t i o n and continuation of plant growth. Since plants form the basic source of energy f o r most l i v i n g matter on earth i t may be concluded that the r e a l l y s i g n i f i c a n t source of energy on the earth i s the sun or more generally what i s known as cli m a t o l o g i c a l environment. The kind of climate dictates what s h a l l be grown., where i t s h a l l be grown, when and how well i t w i l l grow. Tomatoes may be grown i n most regions of Canada but only i n the Okanagan where there i s found that happy combination of warm, sunny days and cool nights, do the plants achieve their r e a l excellence of color and f l a v o r . A l l the nutrients i n the world w i l l not permit the growth of peaches on the p r a i r i e s , f o r i t is said that the severe winter temperatures experienced there provide the l i m i t i n g factor to peach production on the p r a i r i e s . But i t i s equally true that peaches w i l l not grow in d i s t r i c t s where the winter season i s not cold enough t o break the rest period of the t r e e . There i s , therefore, an optimum temperature at which peach trees w i l l winter best. But an optimum temperature i s not confined to the winter season, 2 i t apparently also can vary with the period of growth of the tree i t s e l f . Another and quite d i f f e r e n t optimum temperature may be established f o r the summer's growth period. Therefore i t follows that the optimum temperature at which growth processes are c a r r i e d out i n the plant mast necessarily vary from season to season. I t i s t h i s study of the relationships between ellmate and c e r t a i n vegetative and reproductive phases i n the l i f e cycle of plants that has been named phenology* Although a vast amount of work has been done on the response of plant growth processes to change i n nutrient l e v e l , the phenological approach has been r e l a t i v e l y ignored, p a r t i c u l a r l y during the l a s t s i x t y years. Such apparent neglect of an exceedingly important subject i s d i f f i c u l t to understand, unless consideration i s given to complex problems encountered when an attempt i s made to reproduce the vagaries of climate within the l i m i t e d confines of a laboratory. Without the assistance of modern equipment and building f a c i l i t i e s research was of necessity l i m i t e d i n scope and directed primarily toward the moisture and mineral requirements of plants with some study being made on the e f f e c t s of l i g h t . However, i n t e r e s t i n phenology and i t s p r a c t i c a l applications has been revived recently as a r e s u l t of the construction of modern growth chambers wherein many combinations of l i g h t and temperature can be r e a d i l y synthesized, and also as a consequence of investigations borne from the desire In producers of canner's crops to avoid the "bunching" of vegetable crops at harvest. The l a t t e r reason i s of more p r a c t i c a l s ignificance since such heavy accumulations of vegetables within a very short harvest period have necessitated twenty-four hour labor s h i f t s i n canning f a c t o r i e s with resultant wear and tear on machinery due to improper maintenance schedules. In many instances an i n f e r i o r product i s marketed or even a complete loss of a crop i s experienced because i t i s p h y s i c a l l y impossible f o r the canner to cope with the volume of produce. Unfortunately, vegetable crops deteriorate very r a p i d l y unless properly processed, the time element therefore i s very important, and i f the harvest season can be lengthened i t may enable the canning industry to operate more e f f i c i e n t l y . I t i s imperative then to know the date of harvest considerably i n advance, or In other words p r e c i s e l y how long i t takes f o r a plant to reach maturity from time of seeding. In order to achieve t h i s end, several applications of phenology have been advanced, the most f a m i l i a r one being known as the Heat Unit Theory, The theory assumes temperature to be the dominant fac t o r responsible f o r the various reproductive and vegetative processes i n the plant and ignores the possible e f f e c t of such items as l i g h t ( i n t e n s i t y and duration), moisture, f e r t i l i z e r s and f e r t i l i t y l e v e l i n the s o i l , topography of the land and preceding crops. A formidable array of extremely important growth factors are therefore not considered, however, the method does give some approximation of the growth i n t e r v a l of the plant. V a r i e t a l records are kept, as well as l o c a l temperatures. Calculations are based on remainder indices assuming a base or unit temperature below which growth does not occur. An accumulated summation of heat units i s acquired between phonological periods which may be designated as a summation of degree days i f computations are made on a d a i l y basis, or as degree hours i f made on an hourly b a s i s . A degree day i s found by subtracting a base or u n i t temperature from the mean of the d a i l y maximum and minimum temperatures. That i s , i f the average temperature fo r a s p e c i f i c day was recorded as being 65°F. and the base temperature selected was h2°F* then the number of heat units expressed as degree days would be 23 f o r that day. The number of heat units f o r each day i s accumulated f o r the number of days between phenological period* In c a l c u l a t i n g degree hours the number of degree days i s simply mult i p l i e d by twenty-four* One of the d i f f i c u l t i e s experienced i n the method other than that of the lack of consideration given to the 5. r e l a t e d growth factors mentioned above i s i n the exact determination of phenological periods. With annual vegetable crops t h i s i s not v i t a l l y important as the phenological period can be taken from the time of seeding or date of emergence, to the date of maturity or of harvesting. However, with perennial plants as the deciduous f r u i t trees the phenological periods are extremely d i f f i c u l t to estimate with any degree of accuracy. That i s , should the phenological period begin with the preceding harvest, with the f a l l of the l a s t l e a f before the winter season, with the appearance of the f i r s t bloom i n the spring or the time of f u l l bloom, or even at some l a t e r period? The end of the phenological period presents a si m i l a r problem. Obviously i t should end at maturity of the f r u i t , but maturity indices as presently known are considered i n e f f i c i e n t and u n r e l i a b l e . More precise maturity and storage tests would a i d enormously i n phenological investigations, however, since these maturity indices are not available i t may be possible by ce r t a i n manipulations of temperature and l i g h t to a r r i v e at a good estimate of maturity. That i s , c e r t a i n accumulations of heat units may be r e l a t i v e l y constant over a period of years providing a mathematical index of maturity which could be tested by the subsequent storage q u a l i t i e s of the f r u i t examined. In the spring of the year 1952 an extensive 6. examination of the l i t e r a t u r e on the Heat Unit Theory as applied to vegetables prompted an investigation i n t o the possible a p p l i c a t i o n of the Theory i n forecasting the harvest dates of apples. The formulation of a method f o r the accurate prediction of harvest dates was the main purpose of the study, but i n order to f a c i l i t a t e the examination of the problem ce r t a i n related factors of growth and c l i m a t i c environment had to be considered. These included possible effects of duration of l i g h t , l i g h t i n t e n s i t y , night temperature and of differences i n the loc a t i o n of the study medium. Review of L i t e r a t u r e . Most of the early studies i n phonological and heat summation problems were made i n Europe i n the countries of A u s t r i a , Prance, Belgium, Russia and Germany where the subject attracted the int e r e s t and excited the imagination of b i o l o g i s t s and plant students for many years. In 1905 Professor Cleveland Abbe (1) published a report which was es s e n t i a l l y a summary of the views of the best experimentalists and observers that had been published up to 1891. Much of his subject matter i s reproduced here i n order that a comparison may be made between investigations c a r r i e d out during that period and those being done at the 7. present time. In his report Abbe stated that i n 1735 Reaumur made an exact comparison of the d i f f e r e n t quantities of heat required to bring ra plant up to a given stage of maturity. From observations made i n France, Reaumur adopted the sum of the mean d a i l y temperature of the a i r recorded by a thermometer i n the shade and counting from any given phenological epoch to any other epoch. He employed the average of the d a i l y maximum and minimum temperatures as being a s u f f i c i e n t l y close approximation to the average d a i l y temperature. Even at that time Reaumur was interested i n making a comparison of the sum of temperatures f o r growing periods between years and between l a t i t u d e s . Another worker mentioned by Abbe was Adamson, who i n 1750 disregarded a l l temperatures below °C and took only the sums of the p o s i t i v e temperatures. Gasparin (1) i n l&Vf selected 5°C as the base temperature. In order to a r r i v e at a constant heat product, Boussingault (1) i n I831* computed the t o t a l quantity of heat required to ri p e n grain by multiplying the mean d a i l y temperature of the a i r i n the shade i n centigrade degrees by the 1duration i n days of the process of vegetation. The product was known as the number of day degrees the plant required from sowing to maturity. The problem of discriminating between phenological 8 periods was hotly debated* Quetelet (184-9) working i n Belgium thought there were three great growth periods: l e a f i n g , flowering and ripening* He concluded that the progress of vegetation was i n proportion to the sum of the temperatures or the sum of the squares of temperature calculated above freezing point s t a r t i n g with the awakening of vegetation* However, K a r l F r i t s c h (1881) a f t e r ten years of study at Vienna was more e x p l i c i t as to his d e f i n i t i o n of the phenological periods* His phenological epochs were: 1. The f i r s t v i s i b i l i t y of the upper surface of the l e a f . 2. The complete development of the f i r s t flower. 3» The complete ripening of the f i r s t f r u i t , h. The date at which a tree or bush l o s t a l l i t s f o l i a g e . F r i t s c h used as his s t a r t i n g point January f i r s t f o r both annuals and perennials. He calculated his thermal constants by the sums of the mean d a i l y temperature above zero degrees Reaumur. At about 1850 there were three hypotheses being postulated i n respect to phenology and temperature summations. The f i r s t hypothesis was that f o r the same plant the same stage of vegetation occurred from year to year on the attainment of the same mean d a i l y temperatures. The second was that the same stage of vegetation was attained when i n the course of any year the sum t o t a l of the mean d a i l y temperatures above freezing attained the same value. The t h i r d was to the e f f e c t that the same stage of vegetation 9. was attained when i n the course of any year the sum of the squares of these posi t i v e temperatures attained a c e r t a i n constant value. Each hypothesis had I t s own group of "supporters but no hypothesis was demonstrated as being completely s a t i s f a c t o r y * At the time of Karl Linsser (I867, St* Petersburg) the base temperature accepted was 6°C* Linsser employed base temperatures of 1 ° , 2 ° , 3°> ¥>, 5° and 6°C. He found none that gave any more uniform constant than the o r i g i n a l 6°C* Linsser thought that i n general, at d i f f e r e n t places the same phase of development of vegetation required d i f f e r e n t mean d a i l y temperatures, d i f f e r e n t sums of temperatures and d i f f e r e n t sums of squares of.temperatures* He concluded that there was no zero point that could be adopted which would make these sums equal* He formulated what was c a l l e d Linsser*s thermal law and which stated that i n two d i f f e r e n t l o c a l i t i e s the sums of the po s i t i v e d a i l y temperatures f o r the same phase of vegetation i s proportional to the annual sum t o t a l of a l l p o s i t i v e temperatures f o r the respective l o c a l i t i e s * Linsser thought that i t was not the absolute quantities of heat or nourishing material but rather the r e l a t i v e d i s t r i b u t i o n during the period of vegetation that was s i g n i f i c a n t * Tisserand (1875) introduced sunshine into the discussions and adopted the rule that the work done by a / 10. plant -was represented by the product of the mean temperature and the number of hours of sunshine only r e j e c t i n g useless night time. He, nevertheless, experienced considerable v a r i a t i o n i n l o c a l i t y and between plants i n his c a l c u l a t i o n s . Angot (1882, France) used a base temperature of 6°c. and three methods of c a l c u l a t i o n s : observation of the d a i l y maximum and minimum temperature; the d a i l y means; and l a s t l y by maximum temperature alone. He l a t e r changed to a base temperature of 5°C. because he thought 60C. too high. But no decision was reached as to which was the best method. The d i f f i c u l t y i n f i x i n g the epoch from which the summation should begin was emphasized. He observed that date of sowing ( i n t h i s instance the crop was wheat) was generally taken as the s t a r t i n g point but he recognized that the date of emergence would be better since temperatures of the s o i l and those of the sky were d i f f e r e n t . That s o i l played"an active part i n the growth of the plant was demonstrated by Marie Davy i n 1881. According to him, heat was needed, i n the s o i l i n the early part of the growth of the plant but a f t e r the flower was formed or during the proeess of perfecting the f r u i t sunlight was needed. He thought that any formula which considered temperature alone was a very imperfect presentation of the growth. He demonstrated that i n wheat when the temperature of the s o i l during the l a s t phase of growth, earing to 11. maturity, f e l l below 58° and 60°F., no progress was made i n growth and unless 60°F# was exceeded the crop never ripened properly* Cleveland Abbe summarized his own views and those of the workers mentioned above by noting that i n order to study the influences of climate upon crops one should know the f a c t s about such variables as: the mean temperature of the a i r i n the shade; the mean temperature of a thermometer exposed to f u l l sunshine and wind and placed amid the f o l i a g e of the crop to be studied; the temperature of the s o i l at depths of 1 - 6"; the hydrometric condition of the free a i r ; the v e l o c i t y of the wind or i t s d a i l y movement; the cloudiness of the sky; the t o t a l e f f e c t i v e r a d i a t i o n from the sun and sky; the actual evaporation from the plants and s o i l s ; and also the t o t a l r a i n f a l l as measured by ordinary r a i n gauges i n the experimental f i e l d . He emphasized the great need f o r a laboratory where the vagaries , of climate might be reproduced i n order that plant responses to changes i n temperature and l i g h t might be studied more p r e c i s e l y . Prom 1905 there appeared to be a general d i s -i n t e r e s t i n phenological investigations u n t i l modern impetus was given to the Heat Unit Theory because of i t s apparent value i n the forecasting of harvesting dates f o r vegetables (2, 5, 26, 28, 35> ^6) and f r u i t s such as grapes, pears, 12. peaches, apricots and apples (7> 8, 11> 12, l 1*, 61, 68, 69). The many cl i m a t i c aspects which a f f e c t plant growth are now being investigated. The summation theory has been p a r t i c u l a r l y useful i n forecasting the harvesting dates of vegetables. Bomalaski (10), working with peas, found that the temperature summation for the same variety of plants varied under d i f f e r e n t growing conditions. Generally, the summation was lower i n cooler seasons, due p r i m a r i l y , to the length of the daylight f a c t o r . In peas the maturing process was approximately double i n rate f o r any 18°F. (10 GC.) r i s e i n temperature. According to Bomalaski, growth was slow at the minimum point, but from above minimum to optimum the rate of growth followed Van't Hoff*s Law. Above the optimum point growth f e l l o f f r a p i d l y u n t i l the maximum was reached, beyond which growth stopped. The optimum and maximum were closer than the minimum and optimum. In add i t i o n , peas that were planted early when the s o i l was^ cold matured with a lower number of growing degree days than those planted l a t e i n the season and grown during the warmer temperatures. Bomalaski believed that hours of l i g h t was the prime factor i n the rate of maturity per degree of temperature. Sayre (51), also working with peas, found that the heat u n i t system was the most accurate system yet devised f o r forecasting the maturity of peas because the t o t a l heat 13* summation was the dominant factor a f f e c t i n g the rate of maturity of f i e l d grown peas. Also i t was possible to achieve a more rapid rate of maturity with l e s s heat units due to greater l i g h t i n t e n s i t y and drought conditions. As an i n t e r e s t i n g p r a c t i c a l aspect of the Heat Summation Theory Young (70) reported that the heat u n i t system was help f u l i n forecasting the time of development of the corn borer stages. The degree hours were recorded throughout the season beginning i n winter, using a base of h9°F* Apparently the method could be used i n i n s e c t i c i d a l programs to some advantage. In addition to supporting the Heat-Unit Theory P h i l l i p s 0*5) suggested the use of 5*0°F. as a base temperature f o r sweet corn, 35°F« f o r spinach, 50°F. f o r snap beans, *fO°F. f o r lima beans and f o r peas and 55°P* f o r pumpkins. Livingston (33) outlined the two general classes of temperature e f f i c i e n c y indices, one the remainder indices and the other the exponential Indices• The remainder indices was derived by subtracting a constant quantity, a d a i l y mean at which growth rate was regarded as unity, from each of the temperature data to be employed. The exponential method was based on the supposition that plant growth rates follow the chemical p r i n c i p l e of Van't Hoff which i s that a chemical reaction i s about double with increase i n temperature of 10 GC, or 18°F, He i l l u s t r a t e d by Lehenbauer 1 s work with maize that there was a minimum, maximum and optimum temperature for plant growth and that optimum temperature would vary with the duration of the temperature conditions. He advocated the use of physiology and growth measurements i n r e l a t i o n to c l i m a t i c f a c t o r s as the best possible index of growth, Nuttonson (^2) used a base temperature or zero temperature of 35°F* f o r wheat and f l a x and *fO°F, f o r peas and egg plants. He found that a multiple of the average day length and the summation of day degrees was the l e a s t variable numerical expression. He suggested that the use of days or day degrees alone as a unit of measurement provided mathematical expressions of greater v a r i a b i l i t y than that of the multiple. In other words Nuttonson believed that the t r a n s i t i o n from vegetative to the reproductive stage, as well as the t r a n s i t i o n from the i n i t i a t i o n of growth to market maturity, could occur with some plant v a r i e t i e s under a number of combinations of temperature and day length conditions. He further noted that In his investigations the summation of day degrees required by a l l h o r t i c u l t u r a l v a r i e t i e s appeared to increase i n a southward d i r e c t i o n , that i s , with the decrease of the average length of day duration* Went (63, 6*f, 66) placed considerable emphasis on 15. night temperatures i n the study of plant growth. In his thermoperiodicity investigations the d a i l y l i g h t cycle was given and the effects of temperature during the l i g h t and dark periods considered. He noted that development could be changed by varying temperatures during the dark period; optimal growth i n most plants occurred when the temperature was lower during the night. Thermoperiodicity was the d a i l y cycle of optimum temperature. Went wrote that i n many plants the growth rate stayed constant from day to night; i n others the greater part of the stem elongation Occurred during the night. Therefore the night temperature could be expected to influence the growth rate of the plant as a whole. Camus and Went (16) using three v a r i e t i e s of M c o t i a n a tabacum1 found that both flowering and l e a f habit were affected by night temperature. They discovered that during the early stages of growth the higher the night temperature the fas t e r the stem elongated; but as time progressed the optimal night temperature progressively decreased. They concluded that night temperature was the most c r i t i c a l factor governing developmental processes and that temperature thresholds should be determined f o r d i f f e r e n t species and t h e i r possible r e l a t i o n s h i p to l i g h t i n t e n s i t y studied. A slox* growing v a r i e t y of tobacco was more sensi t i v e to thermal treatments than fa s t e r growing 16. v a r i e t i e s . In an experiment using afternoon shading Went (65) found that some vegetables shaded i n the afternoon had much higher optimal dark temperatures than those with natural night hours. The y i e l d of lettuce and cauliflower decreased by shading but the y i e l d of tomatoes and eggplants was increased. The optimal temperature of the tomato was I3°-18°C.; that of lettuce 8°-13°C. Beets and celery were affected very l i t t l e by afternoon shading. The effects of shading on growth and development i n the vegetative phase were studied by Blackman (6) on sixteen d i f f e r e n t plant species. The r e l a t i v e growth rate was the product of the net as s i m i l a t i o n rate and the l e a f area r a t i o . Any fac t o r which brought about a change i n either the net a s s i m i l a t i o n rate or the l e a f area r a t i o would cause a change i n the r e l a t i v e growth r a t e . The net as s i m i l a t i o n rate i s highest i n f u l l sunlight. That i s , on an approximately logarithmic scale the net a s s i m i l a t i o n rate was p o s i t i v e l y correlated with f a l l i n g l i g h t i n t e n s i t y but the l e a f area r a t i o (leaf area/total plant weight) i s negatively correlated. On Helianthus annuus seedlings the r e l a t i v e growth was dependent on both l i g h t and temperature f a c t o r s . His " r e l a t i v e growth r a t e 0 was defined as the o v e r a l l increase i n dry weight per day expressed as a ; f r a c t i o n of the mean t o t a l plant weight as was governed by 17* the e f f i c i e n c y of the a s s i m i l a t i o n per unit area of l e a f and the t o t a l l e a f area. Optimal l i g h t i n t e n s i t y ranged from 0,5 daylight f o r the shade plant Geum urbanum to 2,51 daylight f o r Medicago s a t i v a , Nightingale (37) grew peach and apple trees i n sand at temperatures of l *5°j 50°, 55° > 60° and 95°F. During the current growing season the maximum y i e l d of roots and tops occurred at 60°P, Nightingale and Blake (39) found that at *+5°F, the Baldwin va r i e t y of apple grew much more than the Stayman v a r i e t y . The f a i l u r e of Stayman to set f r u i t i n the orchard under cool temperatures was att r i b u t e d to i n s u f f i c i e n t nitrogen i n the'tops. The Baldwin v a r i e t y under the same conditions set f r u i t abundantly. Working with peaches Nightingale and Blake 0+0) noted very l i t t l e growth at 1f5°F. and a very rapid growth at 95°F* f o r three or four days a f t e r which growth decreased r a p i d l y . Apparently with peaches, spring and f a l l temperatures are extremely important to growth processes, T In a study with Rome apple trees, Nightingale and M i t c h e l l 0*1) found that the quality as well as the quantity of a plant was a product of the factors of environment. At h0 per cent humidity there was formation of terminal buds, l i g h t green f o l i a g e and an accumulation of carbohydrates. At 95 per cent humidity the leaves were a darker green, there was no formation of terminal buds and the carbohydrates 18. were low i n concentration. The importance of noting precise phenological dates was emphasized by Blake and Davidson (9) i n a study of the growth status of the Delicious apple. They stated that the growth in t e r v a l s to be noted were: 1. As soon as the leaves were one-half to one inch long i n the spring. 2. When spur leaves had almost completed development, or about June 20 - July 1 In New Jersey; 3-« At the time the f r u i t was r i p e . h. A f t e r the leaves had f a l l e n . A d i f f i c u l t y was experienced i n the i n f i n i t e v a r i a t i o n i n vigor and growth between i n d i v i d u a l branches, twigs and spurs on the same tree, even with no serious weather or pest i n j u r y . Their n u t r i t i o n a l investigations showed l i t t l e top growth i n Delicious apples at h5°F. but a considerable accumulation of carbohydrates. At 95°F« the va r i e t y used up carbohydrates f a s t e r than they were manufactured. In an attempt to increase the p r e c i s i o n by which harvesting dates of apricots and prunes might be estimated, Baker and Brooks (3) suggested three methods: 1. To „;.. consider the number of days and the p r o b a b i l i t y that the f,. number of days next year w i l l f a l l within a c e r t a i n i n t e r v a l centred at t h i s mean. 2. The c o r r e l a t i o n of accumulated heat units with the number of days. 3» The employment of R. A. Fisher*s method f o r estimating the r e l a t i o n between heat units and the number of days from f u l l bloom to harvest 19. throughout the season. Actually t h e i r Idea was to increase the accuracy of the number of days to harvest concept by taking i n t o consideration heat u n i t s . They used a base temperature of h5°F» to calculate the heat u n i t s . On examining data on harvesting dates avai l a b l e f o r seventeen years f o r apricots they found a range of nineteen days; with prunes the range was twenty days i n t h i r t e e n years. Mathematically they could predict the harvest date of apricots within three days, eighty per cent of the time and for prunes f i f t y per cent of the time. With apricots the excess heat units shortened the number of days to harvest and t h i s shortening was more marked early i n the season. Brooks (13) improved on the above p r e d i c t i o n method i n a l a t e r work with ap r i c o t s . Here he predicted the harvest date s i x weeks a f t e r f u l l bloom, using two formulae, one based on the c o r r e l a t i o n between the heat accumulated fo r the f i r s t s i x weeks a f t e r f u l l bloom and the period between f u l l bloom and harvest. The other formula predicted the number of days between f u l l bloom and harvest. Ac t u a l l y the computations were based on records of previous years' phenological periods and appeared to be quite precise f o r apricots and somewhat l e s s accurate f o r French prunes and B a r t l e t t pears. I t was possible to obtain an accuracy of within four days one hundred per cent of the time f o r 2 0 . apricots and within s i x days eighty per cent of the time f o r pears. The proper time to begin picking apricots was evidently more d e f i n i t e than i t was f o r pears. However, Brown (15) with the temperature, bloom and harvest records ava i l a b l e to him on Royal (Blenheim) apricots i n the d i s t r i c t around Brentwood, C a l i f o r n i a , applied the heat unit method described by Brooks (13) to the data and found i t less s a t i s f a c t o r y than might have been expected. Brown divided temperature in t o eight classes and worked out a multiple c o r r e l a t i o n c o e f f i c i e n t based on the number of hours In each temperature class for h2 days a f t e r f u l l bloom and also an estimate based on the average of the d a i l y mean temperature f o r s i x weeks a f t e r f u l l bloom. Both predic t i o n methods were considered superior to that of Brooks when applied to the Brentwood data. According to Tufts (58) i n C a l i f o r n i a l o c a l environment rather than l a t i t u d e determined the d i s t r i c t s suitable f o r f r u i t culture. Tufts used apricots as h i s study medium, employed a base unit of 35°F. and three d i f f e r e n t orchard l o c a l i t i e s . He found that the orchard having the cooler temperature had more heat units than the warmer temperature orchard. However, the orchard having the highest number of heat units had extra units c o l l e c t e d at night with warmer night temperatures. This orchard had the e a r l i e s t ripening period, whether due to greater number of, 21. heat u n i t s , the higher-night temperatures or to a more equable temperature could not be determined exactly. At the University of C a l i f o r n i a , L i l l e l a n d (30) studied the e f f e c t of temperature on the growth of the a p r i c o t . Apparently there were three growth periods i n the a p r i c o t , the f i r s t one being a period of rapid increase, the second characterized by much arrested rate of increase and the t h i r d by an accelerated rate of growth which continued u n t i l maturity. The length of these periods could be affected by temperature. L i l l e l a n d calculated the heat units required for each of the growth periods using three base temperatures of 35°> ^2° and 50°F. He found that f o r the f i r s t growth period 50°F. was best, none of the base temperatures t r i e d were suitable f o r the second period and f o r the l a s t period 50°F. was again the most e f f i c i e n t base temperature. L i l l e l a n d manufactured a shelter around a branch of an apricot tree. He raised the night temperature a r t i f i c i a l l y 20°F. higher i n the shelter f o r eight weeks. In th i s manner he shortened the f i r s t period length by 22 days, a c t u a l l y lengthened the second period by f i v e days whence the heat was discontinued. A c t u a l l y the f r u i t i n the shelter stopped rapid growth 22 days ahead of those outside, emerged from the period of depressed growth 17 days i n advance of the other f r u i t on the r e s t of the tree and eventually ripened 21 days e a r l i e r . Apparently the growth of sour cherries may also be 22. divided into three stages. The f i r s t i s a period of rapid development of the f l e s h y pericarp beginning at the time of f u l l bloom. The second i s a period of retarded development of the fleshy pericarp. The t h i r d i s a second period of rapid development of the fleshy pericarp known as the f i n a l swell. Tukey (60) used- a heating method s i m i l a r to that of L i l l e l a n d (30) and by r a i s i n g the night temperature of sour cherries Immediately a f t e r f u l l bloom during stage one was able to decrease the number of days to maturity. The same sort of thing was experienced i n stage two. However, warm temperature l a t e i n stage three lengthened the number of days to maturity. The s i z e of the f r u i t was not s i g n i f i c a n t l y d i f f e r e n t when mature except under the highest temperature conditions where the f r u i t s were smaller. I t was thought s i g n i f i c a n t that the commercial areas of sour cherry production were located i n regions having cool night temperatures during stage three. The same p e r i o d i c i t y of growth, that i s , an early rapid growth, an interim of lesser growth and f i n a l l y a period of very rapid growth was noted i n sweet cherries by L i l l e l a n d and Hewsome (31). Cycle growth was also reported i n the plum by L i l l e l a n d (29). According to Chandler, Kimball, etc. (17), the apple on the average required more c h i l l i n g temperatures before a l l i t s buds opened i n the spring than did most other kinds of f r u i t trees. The c h i l l i n g period must be of at 23. l e a s t two months duration with the temperature below *+8°F#; i f not, buds i n the spring would be considerably delayed and some would open much sooner than others. The c h i l l i n g requirement varied with the v a r i e t y . These workers also observed that a f t e r warm winters the buds opened unevenly. Winter shade was b e n e f i c i a l and i n high humidity the trees were les s prone to shed t h e i r buds unopened or to be too greatly delayed i n opening of t h e i r buds. They emphasized the importance of taking observations from f u l l bloom. Apparently, a prolonged drought could cause apricots to be thrown completely into a rest period. More information on the e f f e c t of winter temperatures was supplied by Eggert (19)> Lamb (27) and M agoon (36) • According to Eggert i n New York State, the percentage of active spur and terminal buds was greater than that of the l a t e r a l buds during the winter period. There was a prolonged re s t period i n l a t e r a l buds. L i t t l e spur bud a c t i v i t y was observed i n November and December but there was considerable a c t i v i t y by January 11. He found too that using a base temperature of 32°F. a l l v a r i e t i e s (Mcintosh, Cortland, Northern Spy and Macoun) had considerable v a r i a t i o n from season to season, but there was a better c o r r e l a t i o n between bud a c t i v i t y and accumulated hours below *f5°F. Ellenwood (20) i n Ohio associated low temperatures i n March and A p r i l with high y i e l d . In apples he stated 2*f. that bud development was rather slow at 55°F« or l e s s * Two or three days of temperatures of 70° to 85°F* when the buds had reached the f u l l pink stage would cause very rapid changes; the influence of the same sort of temperature two weeks e a r l i e r was not nearly as noticeable. I t i s generally recognized that there should be a d e f i n i t e period between blossoming of f r u i t trees and the time at which the f r u i t i s ready to harvest. R y a l l , Smith, etc. (50), - took a base of *fO°F. f o r pears, but experienced rather a l o t of v a r i a t i o n from year to year. They t r i e d a maximum temperature of 90°F. as a base unit but there was no great consistency. They showed that d i s t r i c t s not having extremely high or low temperatures had as great an accumulation of heat units as those with sharper f l u c t u a t i o n s . H a l l e r (2h) showed that f o r three seasons the number of days from bloom to harvest f o r each v a r i e t y of apple was rather consistent under middle A t l a n t i c conditions. Tukey (59) working with several v a r i e t i e s of apple as well as pears, peaches and cherries found that the i n t e r v a l of elapsed time between blossoming and maturity was more constant f o r the apple than for other f r u i t s studied. At Michigan, Gardner, M e r r i l l and Toenges (22) i n an i n v e s t i g a t i o n using the Delicious apple found that environmental conditions during the short period Immediately following f u l l bloom were c o n t r o l l i n g factors i n f r u i t 25. s e t t i n g . The f i r s t week or ten days was shown to be the c r i t i c a l period. They stressed the importance of sunshine during the blossoming period. Lu and Roberts (31*) at Madison, Wisconsin, found the setting of f r u i t through temperature fluctuations varied with v a r i e t y . Delicious blossoms dropped heavily i n warm temperatures above 70°F. but the same temperature did not a f f e c t the Wealthy v a r i e t y . A f i v e day warm period at f u l l bloom caused heavy early dropping; a cool temperature at t h i s time delayed dropping i n the Delicious v a r i e t y . Using trees i n the greenhouse, they found that day temperatures as well as night tempera-tures greatly affected s e t t i n g ; warm days reduced set, cool days tended to increase i t . A United States Department of Agriculture publication (25) reported an i n v e s t i g a t i o n by P h i l i p s wherein the length of the period between f u l l bloom and ripening depended upon the amount of heat received by the t r e e . This period was longest In the P a c i f i c Coast, shortest In the A t l a n t i c Coast and intermediate i n the Central States. Also the period was longer i n the south where i t was warmer, than i n the north. The more rapid maturation i n the colder north was attributed to greater i n s o l a t i o n . However, the evidence was contradictory and generally the p u b l i c a t i o n decided that the number of days from f u l l bloom to maturity was the most r e l i a b l e index to maturity. Their data Indicated that the length of period from bloom to maturity 26. was not influenced by growing season temperatures except with the variety Jonathan where the period was shortened by high temperatures i n the early part of the growing season. An early bloom followed by a cool growing season lengthened the time required to mature f r u i t . Maturity studies i n the apple reported by Haller (25) showed that there were three important factors which might be considered: 1. The change i n the ground c o l o r . 2. The firmness of the f r u i t . 3 . The way the f r u i t i s holding to the tree or the ease of separation and dropping. However, Haller objected to the use of these maturity indices f o r several reasons, the most important being the extreme v a r i a b i l i t y experienced between season and between apples on a single t r e e . Even the si z e of the crop affected maturity as a l i g h t crop matured 5 - 1 0 days e a r l i e r than a heavy crop. Haller divided maturity i n t o f i v e stages, immaturity, early maturity, optimum maturity, l a t e maturity ' and overmaturity with a range of no more than f i v e days f o r each stage of maturity. That i s , one could not be i n an error of more than f i v e days i n a p r e d i c t i o n or the apples would be i n an unsatisfactory stage of maturity. According to H a l l e r temperature differences had a greater influence during c e r t a i n periods than i n others, f o r Instance, early i n the season and l a t e i n the season. Very cold weather, p a r t i c u l a r l y during the f i r s t part of the growing season, could delay maturity. 27. Smith (53) d i d considerable research with growth as affected by clim a t i c factors and found that a l l expressions of growth which could be measured quantitatively while the plants were quite young had t h e i r maximum i n the twenty-four hour day, but as the plants grew older, the maximum gradually was displaced i n the d i r e c t i o n of the shorter day lengths. Smith evolved a complete growth formula, using multiple c o r r e l a t i o n with time as the independent variable and the factors of length of day; mean a i r temperature i n degrees C ; mean d a i l y l i g h t as dependent v a r i a b l e s . His growth constants enabled him to calculate the growth i n t e n s i t y of any combination of l i g h t , day length and temperature corresponding to any geographical p o s i t i o n and season. A s i m i l a r method to that of Smith was used by Clements, Shigeura and Akamine at the University of Hawaii (18) i n a sugar cane i n v e s t i g a t i o n . They used a growth unit defined as "the d a i l y increase i n cane volume, a correlated value of i t obtained by multiplying the d a i l y elongation rate i n centimetres and the green weight of the sheaths per s t a l k of cane". The growth unit was a better measure of growth than a simple l i n e a r elongation since i t tended to be a measure of volume growth. After considerable work with p a r t i a l regressions involving such factors as: green weight of sheaths, age, sheath moisture, r e l a t i v e 28. humidity, wind v e l o c i t y , maximum temperature, minimum temperature and l i g h t , they concluded that wind v e l o c i t y , humidity and sheath moisture could be disregarded without destroying the e f f i c i e n c y of the predic t i o n equation. They, l i k e Smith (53)j developed a growth formula, only t h e i r formula was applicable to sugar cane. Thornthwaite (57)> working at Seabrook, New Jersey, evolved a growth unit defined as "the amount of development that would occur i n a plant while a unit amount of water was being transpired". The units were given i n the metric system; 100 growth units corresponded to 1.0 cm. of water (about Omk inches). He believed that the water need of a plant and the growth index were the same and consequently the curve of the mean d a i l y water need also showed the d a i l y growth index. Throughout the year growth units accumulated slowly at f i r s t , more and more r a p i d l y u n t i l midsummer and f i n a l l y more and more slowly u n t i l the end of the season. The curve related growth and development with time and translated the c i v i l calendar i n t o the climatic calendar. Hours and days became growth u n i t s . He employed an instrument known as the evapotranspirometer f o r measuring evaporation and t r a n s p i r a t i o n . Through a detailed observation of peas and by the use of a transpirometer he found a r e l a t i o n s h i p between climate and the plant's water needs. That i s , since t r a n s p i r a t i o n , growth and development were 29. a l l proportional to each other and were a l l affected by temperature i n the same way he was able to work out a crop calendar i n a s l i d e rule whereby he could predict harvest dates from any planting date or vice versa. In general i t would appear that phenology and i t s p r a c t i c a l applications have been and are being examined with considerable i n t e r e s t and determination. The d i f f i c u l t i e s Inherent i n the study of such a subject are f u l l y appreciated. For one thing there i s the complexity of f a c t o r s , physical, chemical and environmental, which contribute to the growth processes within the plant. Then there i s the matter of combining or c o r r e l a t i n g a l l these factors into a mathematical expression which w i l l r e s u l t i n a coherent, reproducible and accurate formula f o r p r a c t i c a l p r e d i c t i o n purposes. Suggested methods of computation range from the Involved multiple c o r r e l a t i o n concept to the very simple remainder i n d i c e s , and each may be able to contribute something toward a f i n a l , successful s o l u t i o n . F i n a l l y , there i s the indisputable f a c t that the problem concerns l i v i n g material, with a l l i t s countless variations and i n d i v i d u a l idiosyncracies, tremendous obstacles to any i n v e s t i g a t i o n . However, being able to recognize and name the troublesome characters i s i n i t s e l f an advantage and i f one can judge by the accumulation of l i t e r a t u r e on the various phases of study, phenology has an important place i n 30. b i o l o g i c a l research. Materials and Methods The procedure of the i n v e s t i g a t i o n l e n t i t s e l f r e a d i l y to a d i v i s i o n i n t o three parts. The f i r s t one, preliminary i n nature, involved the simple c a l c u l a t i o n of degree days and the compilation of hours of sunshine f o r several important apple v a r i e t i e s and covering a period of four years. The second part was an i n t e n s i f i c a t i o n of the i n v e s t i g a t i o n followed i n the f i r s t part but with c e r t a i n s i m p l i f i c a t i o n s and additions. Here, only one v a r i e t y and root, namely Mcintosh on East Mailing I , was studied. The entire scope of the project was enlarged to include data from the year 1952. Various combinations of several base temperatures were examined, together with refinements i n the s t a r t i n g point and duration of the phenological period. Sunshine records were again tabulated as well as minimum and night temperatures. Solar r a d i a t i o n was introduced as a new f a e t o r . The t h i r d and f i n a l phase increased the range of years f o r which degree days were calculated and r e s t r i c t e d the study to temperature e f f e c t s alone. I t also brought i n the e f f e c t of l o c a t i o n by u t i l i z i n g data from the Experimental Station at Summerland, B. C. Under ac t u a l f i e l d conditions a study was made on the growth of apples during the season of active growth and i t s possible r e l a t i o n to the 31. average temperature. Part I A series of calculations were made beginning with an examination and subsequent compilation of meteorological data f o r the years 19^ 8-1951 available from the records of the D i v i s i o n of F i e l d Husbandry at the Central Experimental Farm, Ottawa, Ontario. Averages of the d a i l y maximum and minimum temperatures recorded at Ottawa were calculated and then using the simple remainder indices described by Livingston (33)> with unit or base temperatures of h2°F* and 5*0°F. respectively, degree days were calculated f o r each month of the growth period of apples. Precise phenological data on the dates of blooming and harvesting were taken from the records at the D i v i s i o n of Horticulture f o r the years 191+8-1951. The beginning of the phenological period was taken as being the date of f i r s t bloom, the end of the period being the day previous to the actual harvesting of the f r u i t . Several of the more important and use f u l v a r i e t i e s , such as Melba, Hume, Mcintosh, Lawfam and Sandow, grown at the Farm were selected. The phenological dates chosen were an average computed from two to th i r t e e n trees depending upon the number of trees ava i l a b l e f o r the v a r i e t y and root concerned. Trees were taken from Section I of the Standard Orchard at Ottawa, as that Section had had f a i r l y uniform c u l t u r a l treatment since i t was planted i n 1936. 32. Prom the records of the d a i l y hours of sunshine, the t o t a l hours of sunshine were compiled f o r the phenological periods of the Mcintosh v a r i e t y i n the years 19^ 8-1951 and tabulated with the number of degree days f o r the same period. S t a t i s t i c s on the hours of sunshine and degree days were calculated f o r harvest dates of the Mcintosh v a r i e t y kept by the Record Section of the H o r t i c u l t u r a l D i v i s i o n and also f o r harvest dates recorded i n maturity tests made by the Cold Storage Research Section. Part I I Since the material covered i n the preliminary i n v e s t i g a t i o n seemed inadequate i t was decided to extend the study to include the factors of solar r a d i a t i o n , night temperatures and minimum temperatures. A single v a r i e t y and root, that of Mcintosh on Bast Mailing I , was selected. Thirteen trees from Section I of the Standard Orchard were used f o r t h i s i n v e s t i g a t i o n . In addition to the use of base temperatures of h2°F. and 50°P. already employed i n the previous work, degree days i n t h i s i n v e s t i g a t i o n were calculated with base temperatures of 3h°F» and 38°F. f o r the growing season of the apple during the years 19^8-1952. The above base temperatures were selected from suggestions i n the l i t e r a t u r e . Various combinations of these base temperatures were employed 33. throughout each growing season to ascertain whether (as i s apparently true of other f r u i t s ) there are optimum temperatures f o r c e r t a i n stages of plant growth. In the apple, f o r instance, during the month of May a base temperature of 50°F. might be selected from which to calculate the degree days; the assumption being that temperatures above 50°F. are the optimum f o r that stage i n the development of the apple. In the month of June, assuming a d i f f e r e n t growth temperature optimum, a base of h2°F. might be used. The same or d i f f e r e n t base temperatures could be employed i n the remaining months of the growing season. In t h i s manner a system of d i v i d i n g the growth period i n t o a series of possible optimum temperatures l e v e l s was derived. An example of th i s combination of several base temperatures i s i l l u s t r a t e d i n Table 3, which shows the degree days by month f o r the years 1950 and 1952. Each combination of base temperature i s given a series l e t t e r , A, B, C, D, etc. In series G, 50°F. i s used as a base temperature throughout the phenological period. To i l l u s t r a t e the refinements possible by sel e c t i n g a beginning of the phenological period other than f u l l bloom on the t o t a l number of degree days, a table was set up to make a comparison between the t o t a l degree days as calculated from f u l l bloom and the t o t a l degree days as calculated from ten days before f u l l bloom. 3k. Some conjecture as to the p o s s i b i l i t y of the employment of minimum temperatures rather than average temperatures prompted the construction of a table (Table 6) i n which h2°F» was subtracted from the minimum d a i l y temperature during the phenological periods f o r the years 19^8-1952* This i s p r e c i s e l y the same as the normal degree day c a l c u l a t i o n , but the r e s u l t i s tabulated here simply as 'X' un i t s to d i f f e r e n t i a t e from the degree days* In order to estimate the importance of night temperature on the growth and maturity of the apple, the night temperatures f o r the growth periods during the years 19M3-1952 were calculated a f t e r Went's formula (62)* That i s , the night temperature was found by adding one-quarter of the difference between maximum and minimum temperatures to the minimum temperature* I t was assumed that a higher night temperature i s more conducive to growth of deciduous f r u i t s , therefore a base of 5"0°F* was subtracted from the d a i l y night temperature* For example, i f the average night temperature was 60°F*, then a f t e r subtracting a base of 5*0°F. the r e s u l t i n g 10°F* could be interpreted as being 10 'Night 1 units* These units were accumulated f o r the growing season i n the ordinary way. The t o t a l 'Night 1 units were calculated by month f o r the years 19^8-1952. The 'Night* units were then l i s t e d with the t o t a l degree days f o r the same years i n order that a comparison might be made of the e f f i c i e n c y of 35. each method i n the pr e d i c t i o n of harvest dates. The average calculated night temperature was subtracted from the average d a i l y temperature and the to t a l s found f o r each growing season i n the years 1S&-8-1952. This was intended as a measurement of the f l u c t u a t i o n e x i s t i n g between day and night temperatures. The units here were not calculated using base temperatures. That i s , i f the calculated night temperature.was 6o°F. and the average d a i l y temperature 85°P«, then when the night temperature was subtracted from the average temperature, the r e s u l t i n g 25°F. was interpreted as being 25 u n i t s . These units were again accumulated f o r the growth season as i n the c a l c u l a t i o n of the t o t a l number of degree days. The hours of sunshine were compiled by month f o r the years 19^8-1952 and the t o t a l hours of sunshine tabulated f o r each growing year. The dates of f u l l bloom and of harvest, the t o t a l number of days i n each phenological period and the average number of hours of sunshine per day were included i n t h i s s e r i e s . Sunshine was taken as a measurement of l i g h t i n t e n s i t y . Solar r a d i a t i o n was next considered and a table drawn up showing the amount of r a d i a t i o n per month f o r the years 1950-1952. No solar r a d i a t i o n data are avail a b l e before June 1 ^ 9 . In some instances the data f o r i n d i v i d u a l days were missing. Accordingly the r a d i a t i o n was calculated 36. a f t e r a method suggested by Mr* G. W. Robertson, Meteorologist at the Central Experimental Farm. The method involved the use of the formula Rc = RA (a - b^) where Rc i s the measured r a d i a t i o n , R^ i s a t h e o r e t i c a l maximum t o t a l d a i l y r a d i a t i o n at the top of the atmosphere, a and b are unknown constants which were calculated as being 0.27 and 0.5^ respectively f o r the Ottawa l a t i t u d e ; n i s the t o t a l hours of sunshine, and N i s the maximum possible hours of sunshine. Table 10 l i s t s the maximum hours of daylight and the t h e o r e t i c a l maximum t o t a l r a d i a t i o n at the top of the ~ atmosphere at Ottawa f o r the s p e c i f i c dates shown. From these data the solar r a d i a t i o n units f o r the missing days were calculated. Solar r a d i a t i o n units are expressed In Langleys, a Langley being the unit used to denote one gram c a l o r i e per square centimetre of normal surface. Part I I I In the spring of 1953 i t was decided to i n t e n s i f y the i n v e s t i g a t i o n with regard to temperature alone. Here the main purpose was not so much to predict the harvest date but rather to study the growth processes of the apple as affected by temperature. I t was thought that i n t h i s manner i t might be possible to arr i v e at a more accurate base temperature or temperatures from which to calculate degree days and ultimately predict the harvest date. However, before t h i s experiment was begun the 37. previous year's temperature investigation was broadened to include the years 19 -^0-1952 at Ottawa. The possible differences due to l o c a t i o n were also to be noted by having si m i l a r data examined from Summerland, B. C. The Summerland data were incomplete as harvest dates were not recorded during the War. Data were available f o r the years 19^0 and 19^ 1 and continuously from lS*f6-1952. Temperature and phenological data from both Ottawa and Summerland were compiled at Ottawa. The study medium was again Mcintosh on East Mailing I . Degree days were calculated using base temperatures of 50°F., W ^ . , ^-2^. and 3^°F. f o r both Stations. Dates of f u l l bloom and harvest, t o t a l number of days i n the phenological period as w e l l as the t o t a l degree days were included In the tables constructed. The beginning of the phenological period was taken as ten days before f u l l bloom i n a l l instances. Upon completion of t h i s work a comparison of the t o t a l number of degree days at Ottawa and at Summerland was made by years and by base or unit temperature. The i n v e s t i g a t i o n into growth and temperatures i n the f i e l d was I n i t i a t e d on the f i r s t of June 1953. At t h i s time the bloom on early and l a t e v a r i e t i e s had disappeared and small apples were being i n i t i a t e d . A tree of an Ottawa s e l e c t i o n , 0-277* which i s a cross between the v a r i e t y Melba and the variety Crimson 38. Beauty and consequently an early maturing v a r i e t y , was set aside f o r observation purposes. Four d i f f e r e n t spurs selected at random around the tree were l a b e l l e d on June 1, well a f t e r the n o n - f e r t i l i z e d blossoms had f a l l e n . The number of immature apples varied from one to f i v e on each spur. A c t u a l l y a t o t a l of seventeen apples were measured i n the I n i t i a l phase. However, by June 17, a l l but seven of these had been eliminated by the June drop. A vernier c a l i p e r manufactured by the Central S c i e n t i f i c Company and graduated i n millimetres was used to measure the equatorial diameter of"the apple. I t was possible by means of the vernier scale to achieve an accuracy of measurement up to one one hundredth of a centimetre. Measurements were taken around noon each Monday, Wednesday and Friday of the week. On July 26, the 0-277 tree was attacked by ch i l d r e n who f i l c h e d four of the apples which had been l a b e l l e d . The apples at t h i s time were quite r i p e , but the tree was not picked completely u n t i l August *fth. Growth measurements were made up to an including August 3rd on two apples. Of the data co l l e c t e d from the 0-277 seedling only those measurements beginning on June 5 and continuing to July 2k were included i n this study. These data represent s t a t i s t i c s gathered on seven apples. Three trees of the v a r i e t y Mcintosh on East Mailing I were also marked fo r observation purposes and four 39. j spurs on each tree l a b e l l e d i n a s i m i l a r manner to that employed with the 0-277 seedling v a r i e t y . A t o t a l of f o r t y apples were examined In the i n i t i a l phase. Unfortunately with the Mcintosh v a r i e t y most of the apples marked f e l l o f f during the June drop. In f a c t only one apple of a l l those examined on each tree survived the drop. However, on June 2h the date at which the June drop appeared to be over, three new apples on each tree were selected at random and l a b e l l e d , making a t o t a l of four apples marked f o r study on each tree. Equatorial measurements on the twelve apples were taken throughout the summer and autumn around noon every Monday, Wednesday and Friday. On September 25 the l a b e l l e d apples on one tree were accidently picked by harvesting crews. Therefore complete data on twelve apples were a v a i l a b l e only from June 26 to September 23, although the l a s t l a b e l l e d apple did not drop o f f the tree u n t i l October 5* - The average temperature per day was calculated from records supplied by the Meteorological Section of the D i v i s i o n of F i e l d Husbandry, C. E. F., Ottawa, f o r the active growth period of the 0-277 seedling and of the Mcintosh on East Mailing I apples. The average growth or increase i n equatorial diameter was determined from the f i e l d observations. Two c o e f f i c i e n t s of c o r r e l a t i o n were calculated f o r the r e l a t i o n s h i p between average increase i n size and average temperature. In one instance, the ho. c o e f f i c i e n t of c o r r e l a t i o n was based on a study of the 0-277 seedling with seven apples and twenty-two observations; while i n the other the c o e f f i c i e n t of c o r r e l a t i o n was based on measurements taken on the Mcintosh on East Mailing I v a r i e t y with twelve apples and thirty-nine observations* Results of the Investigation Part I Four years temperature data co l l e c t e d during the active growing season at Ottawa, Ontario, are presented below i n Table No. 1. Table I Average Monthly Temperatures For The Years l<ft-8-195l at Ottawa Degrees Fahrenheit MoAth, 1^8 1^-9 ipx Average May 53.'6 5W9 55.1 56.7 55.1 June 62.9 68.3 6h.l 62.7 6>.5 July 69.1 71 .5 68.3 68.5 69.H-August 68.9 69.'9 (h.l (b.2 66.8 September 61.3 56.2 57.8 57.6 Average 63.2 G+.2 61.9 61.1+ 62.7 The above table shows that monthly temperatures ranged from an average of 55.1°F» i n May to 69.h°F. i n July. In a l l years July was the warmest month. The grand average f o r the four year period was 6 2 . 7 ° ? . Table I fa)-Average Degree Days Prom F i r s t Bloom to Harvest Bv Variety at Ottawa (Record Section) Base Jf2°F. Variety 19 -^8 l<ft-9 1950 1951 Average Melba 2172 2188 1995 I960 2079 Hume 2586 2918 2568 2559 2658 Mcintosh 2919 3072 2672 2812 2869 Linda 3019 298^ 2710 2&ik 2889 Edgar 3072 3251* 2779 290? 3003 Lawfam 3071 325^ 2732 2966 3006 Famous e 3075 32*f8 2698 3067 3008 Sandow 31*+2 320U- 2812 2910 3031 Niobe 311*-3 332k 2903 3052 3108 [ Base 50°PW Variety 19*f8 19^f9 1950 1951 Average Melba 1^27 1^96 1329 127 -^ 1382 Hume 17*f8 1999 1680 1657 1771 Mcintosh 1936 2075 1716 iQOh 1881 Linda 1976 2020 1732 182 -^ 1888 Edgar 2021 21^1 1765 l 8 6 l 19N-? Lawfam 2020 21*fl 1737 188>+ 19>4-6 Fameuse 2022 2130 1719 1905 1 9 ^ Sandow 2031 2119 1781 1883 1951* Niobe 2030 2183 1812 1918 1986 The average number of degree days calculated from base temperatures of h2°Fm and 50°F. as given i n Table No, 1(a) shows that the early v a r i e t i e s Melba and Hume required fewer degree days to mature than did the l a t e r v a r i e t i e s Fameuse and Niobe. Using a base of ^2°F#, Melba required an average of 2,079 degree days f o r the four years 19^8-1951 to bring i t to harvest maturity; while f o r the same period Niobe required an average of 3>108 degree days, a difference of 1,029 degree days. With a base temperature of 5"0°F. a simil a r trend was shown except the difference between the two v a r i e t i e s was only 60h degree days. The v a r i e t i e s Edgar, Lawfam and Fameuse required almost the same number of degree days to bring them to harvest maturity. Table K b ) Degree Days by Month f o r the Years 19^ 8-1951 Base *+2°F. Month, Year May June Attest, Seotember October 19^8 357 11? - -636 21 850 27 838 27 588 20 158 5 l ^ f 9 399 1 3 7 796 27 913 29 871 28 k27 Xh 10 302 1950 h!5 13 ; 671 22 822 27 698 23 391 13 7 232 1951 k6? 1 5 7 631 21 828 27 705 22 >*83 16 7 230 & Average number of degree days per day Table 1(b) shows that as f a r as the t o t a l number of degree days per month was concerned there was a r i s e i n the number to a peak In the month of July, whence the degree days dropped o f f again. Of p a r t i c u l a r i n t e r e s t f o r harvest p r e d i c t i o n work was the average number of degree days per 4-3. day i n the month of September. During September t h i s average ranged from t h i r t e e n degree days i n the year 1950 to twenty degree days i n the year 194-8. The average number of degree days per day during September over the four years 194-8-1951 was sixteen. Table 2 shows phenological data arranged from records kept by the Low Temperature Storage Section. feble 2 Low Temperature Storage Maturity Records, Variety Mcintosh. Base Temperature h2°F. Date of Date of Year F i r s t Bloom CHarvest No. of Days i n Phenological Period T o t a l Degree Davs *. Hours of Sunshine 123 2902 1006.8 130 3*4-3 1070.3 12^ 2685 918.3 132 294-5 920.2 127 2919 978.9 19^ -8 May 20 Sept. 21 194-9 May 13 Sept. 21 1950 May 2h Sept. 26 1951 May 16 Sept. 26 Average I t can be seen that f o r the va r i e t y Mcintosh the t o t a l number of degree days varied from 2,685 i n 1950 to 3,14-3 i n 19^ -9, a difference of 4-58 degree days. The difference i n the actual number of days from f i r s t bloom to harvest f o r the years 1950 and 19**9 was only s i x days. From the average t h i s deviation was only three days f o r each year. There appears to be no consistent r e l a t i o n s h i p between the hours of sunlight and either the t o t a l number of degree days or the t o t a l number of days between f i r s t bloom and harvest. Part I I The several combinations of base temperature upon which degree days were calculated i s outlined i n Table 3 f o r the two years 1950 and 1952. This table shows that a high base temperature i n the spring followed by a low summer base temperature and ending the season with a comparatively low base temperature (Series A) was not e f f e c t i v e i n increasing the p r e c i s i o n of the t o t a l number of degree days from year to year. Nor d i d the low base temperatures used i n Series C increase the p r e c i s i o n . In Series F a base temperature of 50°F. i n May, followed by a base temperature of *f2°F. i n June, 3h>°F. i n July and August and 50°F. i n September reduced the difference between the t o t a l degree days f o r the two years to 364-, the same as that found using a s t r a i g h t base temperature of 50°F. throughout the season.' Table 3 Degree Days Prom F u l l Bloom to Harvest With Various Combinations of Base Temperatures i n Degrees F« By Month f o r Years 1950 and 1952 at Ottawa  Year 1950 Year 1952 Month Month; Series May June July August September Total May June July August September Total 2933 3093 A 50° 50° 38 431 34° 1070 42° 698 42° 285 2522 50° 82 50° 34° 467 1157 42° 768 42° 459 Difference between years 411 B 3 34° 50° 102 431 34° 1070 42° 698 42° 285 2586 34° 242 50° 34° 467 1157 42° 768 42° 459 Difference between years 507 -C , 3 4 ° 38° 102 791 34° 1070 42° 698 42° 285 2946 242 38° 34° 822 1157 42° 768 42° 459 Difference between years 502 D 50° 50° 38 431 34° 1070 34° 946 42© 285 2770 50° 82 50° 34° 467 1157 3 4 Q 1016 42° 459 Difference between years 411 3448 3181 Year 19fQ Month Series May June July August September E 50° h2° 3^° 3k° h2° 38 671 1070 9^6 285 Difference between years 4-11 F 50° h2° 3h° 3 ^ Q 50° 38 671 1070 9^ -6 1*4-8 Difference between years 36*+ G 50 0 50° 50° 50° 50° 38 4-31 57k h$o l*f8 Difference between years 36*f Table "\ (Continued) Year ;L9?2 Month, Tot a l May June July August September T o t a l 50° h2° 3h° 3 k Q h2° 3010 82 702 1157 1016 M-59 3^ -21 50° 4-2° 3h° 3hQ 50° 2873 82 702 1157 1016 275 3237 50° 50° 50° 50° 50° 16I+1 82 4-67 661 520 275 2005 Table 4-Total Degree Days by Years (194-8-1952) From F u l l Bloom'to Harvest With Di f f e r e n t Base Temperatures (Ottawa) Year Base Deviation From Averaee . Base ^8°F. Deviation From Averaee Base 4-2^. Deviation From Averaee Base 50°S Deviation From Averaee Series F Deviation From Averaee 19*4-8 3807 30 3332 33 2855 35 1904- 39 3136 39 1 ^ 9 3905 128 34-33 134- 2961 14-1 2016 151 324-8 151 1950 34-58 319 3002 297 254-6 274- 164-1 224- 2873 224-1951 3710 67 3214- 85 2734- 86 1758 107 2990 107 1952 4-005 228 3515 216 3005 185 2005 14-0 3237 14-0 Average 3777 3299 2820 1865 3097 48. Table 4 shows that when the number of years examined was extended to include the years 1948-1952 the deviation from the average shows that there Is l i t t l e to choose between the employment of one temperature base throughout the season and the combination, Series F, as shown i n Table 3» The deviations from the average were exactly the same f o r the base temperature of 50°F. and the Series F temperatures* Actually the base temperature of 42°F. appears to be most s a t i s f a c t o r y f o r a l l years, but considerable v a r i a t i o n from the average was noted from year to year even with that base temperature* Tables 5 and 5(a) show that s t a r t i n g the phenological period ten days before f u l l bloom rather than at f u l l bloom Increased the p r e c i s i o n of the t o t a l degree days. In 1948 with a base temperature of 34°F* there i s a deviation of t h i r t y degree days from the average when the phenological period was started at f u l l bloom. St a r t i n g the growing season ten days before f u l l bloom r e s u l t s i n a deviation of only s i x degree days from the average using a base temperature of 34°F* A si m i l a r trend i s shown f o r Series F base temperatures and f o r the other years tabulated. Table ? Deviation of Total Degree Days From the Average, Five Different Base Temperatures. Years 1948-1952 at Ottawa  Base Base Base Base Base Temp. Temp. Temp. Temp. Temp. Year 34°F. Deviation 38°F. Deviation 42°ft. Deviation 46°F. Deviation 50°F. Deviation 1948 3982 6 3467 18 2950 1 2434 1 1931 9 1949 4115 127 3677 192 3091 140 2581 148 2067 145 1950 3740 248 3244 241 2748 203 2251 182 1763 159 1951 3927 61 3391 94 2871 80 2346 87 1826 96 1952 4174 186 3644 159 3094 143 2554 121 2022 100 Average 3988 3485 2951 2433 1922 Phenological period begins 10 days before f u l l bloom. Tab^e 5(a) Base 3k°F. 3807 3905 3458 3710 4005 3777 T o t a l Degree Days by Years f o r Two Periods at Ottawa 1. F u l l Bloom to Harvest 2, 10 Days Before F u l l Bloom to Harvest F u l l Bloom to Harvest Deviation From Average 30 128 319 67 228 Series F 3136 3248 2873 2990 3237 3097 Deviation From Average 39 151 < 224 107 140 10 Days Before F u l l Bloom to Harvest Deviation Base From 3io;. Average , 3982 4115 3740 3927 4174 3988 6 127 248 61 186 Series I 3163 3289 2995 3068 3254 3154 Deviation From Average 9 135 159 86 100 2 J 51. Table 6 was compiled by using the minimum temperature instead of the average temperature from which to subtract a base temperature. Table 6 Minimum Temperature Minus Base of 4-2°F. By Month f o r the Years 1<&8-1952 - Ottawa Month Total Deviation Year May June July August September 'X* units From Average 194-8 ^3 292 4-85 495 221 1536 32 194-9 73 4-74- 537 4-77 116 1677 109 1950 118 365 505 371 126 14-85 83 1951 14-1 339 4-99 34-7 154- 14-80 88 1952 91 363 553 4-19 235 1661 93 Average 1568 Period i s from 10 days before f u l l bloom to harvest. The calculated night temperature as shown i n Table 7 reveals no consistency over a f i v e year period except i n 1950 and 1951 when there was a difference of only two 'Night* units.' Table 7 Night Temperature Minus Base 50°F. By Month and Year - Ottawa Month Deviation Total Deviation Total From Degree Days From Year A p r i l May. June July August September 'Night* Units Average"' Base 50°F. Average 194-8 16 227 4-17 4-12 161 1233 3 1931 9 194-9 4-7 397 4-75 4-18 74- 14-11 175 2067 14-5 1950 77 279 4-09 281 69 1115 121 1763 159 1951 99 24-0 4-08 273 97 1117 119 I826 96 1952 33 284- 4-77 338 173 1305 69 2022 98 Average 1236 1922 Period i s from 10 days before f u l l bloom to harvest* V J \ ro 53. Table 8 Average Twenty-Four Hour Temperature Minus Calculated Night Temperature By Month and Year - Ottawa Month, Deviation Average Tot a l From For Last Year May June July August Sent. 'Y* Units Average ' 5 Days lS^ -8 73 172 185 178 129 737 1 5.2 l9*+9 119 167 200 205 75 766 30 5.2 1950 86 161 165 171 97 680 56 h.6 1951 14-2 159 172 176 103 752 16 5.2 1952 93 183 163 182 122 7^ 3 7 5.0 Average 736 Period i s from 10 days before f u l l bloom to harvest. In Table 8 the calculated night temperatures are subtracted from the average d a i l y temperature and o r i g i n a l l y were aimed at some sort of measurement of the f l u c t u a t i o n between night and day temperatures. A c t u a l l y t h i s procedure may be reduced to simply a summation of one-quarter of the d a i l y maximum minus the d a i l y minimum temperatures f o r the phenological period and gives the range between maximum and minimum temperatures. The t o t a l number of •Y1 units c a l c u -l a t e d i n t h i s manner f o r each year shows less deviation from the f i v e year average than any other system yet attempted. The deviation from the average varied from f i f t y - s i x i n 1950 to one i n 19M-8. Table 9, Hours of Sunshine by Month f o r the Years 1948-1952 - Ottawa Month Wo* Average Year Date of F u l l Bloom May June July August September Harvest Date Total of Days Per Day (HoursJ 1948 May 28 113.2 210.9 299.5 257.1 156.5 Sept. 24 1037.2 129 8.04 1949 May 21 160.6 233.9 309.7 278.9 92.5 Sept. 16 1075.6 118 9.12 1950 May 28 97.8 242.9 249.6 223.6 110.4 Sept. 19 924.3 124 7.45 1951 May 21 175.7 167.9 263.6 202.9 126.9 Sept. 20 937.0 132 7.10 1952 May 22 115.3 284.8 300i3 273.9 121.1 Sept. 24 1095.4 135 8.11 Period i s from 10 days before f u l l bloom to harvest. 55. Table 9 Indicates that there i s apparently l i t t l e r e l a t i o n s h i p between the t o t a l hours of sunshine and the t o t a l number of days i n the phenological period. In 1951 there were a t o t a l of 937 .0 hours of sunshine i n the growing period which consisted of 132 days, but i n 1949 the actual records showed a t o t a l of 1075.6 hours of sunshine with only 118 days i n the active growth period. The year 1949 had the larges t average number of hours of sunshine per day of the years l i s t e d , and matured apples i n the shortest time. The year 1951 had the lowest average hours of sunshine per day but only three days l e s s were required to harvest mature the apples than did the year 1952 during which almost an hour of sunshine more per day was recorded during the active growth of the apple. The data i n Table 10 represents basic calculations of the maximum possible hours of sunshine and the t h e o r e t i c a l maximum t o t a l r a d i a t i o n f o r Ottawa. From these data a curve can be constructed which w i l l give the ma^-*™^™ possible hours of sunshine and t h e o r e t i c a l t o t a l r a d i a t i o n f o r any day of the year. Once these data "have been computed i t Is possible using the formula, Rc - (a - b^), suggested by Mr. Robertson to ar r i v e at the number of solar r a d i a t i o n units f o r that day. 56. Table 10' Date Maximum Hours of Daylight at Ottawa Latitude 45° - 24« N March 21 12.20 A p r i l 13 13.38 May 6 14.48 May 29 15.32 June 22 15.63 July 15 15.30 August 8 14.40 August 31 13.43 September 23 12.15 October 16 10.95 November 8 9.87 November 30 9.07 December 22 8.75 January 13 9.10 February 4 9.91 February 26 10.98 Theoretical Maximum Total Radiation At T O P of Atmosphere 626 767 887 964 990 960 878 759 618 474 352 270 241 272 356 481 T*l***r,t*K finnnvi T"»r*t ff*0 >fr Or raw* Ov M.«T« 57. Table H, Solar Radiation By Month f o r Years 1950-1952 At Ottawa Month Year A p r i l May June July August September1 Total 1950 6685 16027 17120 13020 7061 59913 1951 11661 11+620 16621 13592 7578 64072 1952 924-5 18364- 18008 154-83 8559 69659 Period i s from 10 days before f u l l bloom to harvest. A tabulation of the solar r a d i a t i o n by month at Ottawa as recorded i n Table 11 shows considerable v a r i a t i o n between years and between the same month In d i f f e r e n t years. In May, 1950, there were 6,685 Langleys recorded; 11,661 Langleys i n May of 1951 and 9*24-5 Langleys were observed i n May of 1952. Other months were s i m i l a r i n t h e i r variance. The t o t a l number of Langleys varied from 59>913 i n 1950 to 69,659 Langleys i n 1952. Table 12 Climate-logical and Phenological Data Gathered at Ottawa For Years 194-8-1952 No. Total Total Total Total Night Date of Harvest of Degree Days Hours of Solar Temperature Year F u l l Bloom Date Days Base 50°F. Sunshine Rad^Atiofl Minus 50?F. 194-8 May 28 Sept. 24- 129 1931 1037.2 1233 194-9 May 21 Sept. 16 118 2067 1075.6 14-11 1950 May 28 Sept. 19 124- 1763 924-.3 59913 1115 1951 May 21 Sept. 20 132 1826 937.0 64-072 1117 1952 May 22 Sept. 2k 135 2022 1095.4- 69659 1305 Period i s from 10 days before f u l l bloom to harvest. 59. In Table 12 the various c l i m a t o l o g i c a l and phenological factors are grouped f o r purposes of comparison. There appears to be a r e l a t i o n s h i p between t o t a l solar r a d i a t i o n , hours of sunshine, and t o t a l degree days f o r the years 1950-1952. The year 1952 had more solar r a d i a t i o n u n i t s , hours of sunshine and t o t a l degree days than any of the other years tabulated with the exception of 19^9 which had a larger t o t a l number of degree days. That year (1952) required the greatest number of days to mature the Mcintosh apple. The warmest night temperatures were recorded i n 19^ -9 and also the l e a s t number of days to maturity were required, but t h i s trend was not followed In a l l years. For instance, the year 1950 had the coldest nights but yet required only 12h days to mature the apples, while i n 1952 the warmer nights required 135 days to mature the Mcintosh va r i e t y of apple s u f f i c i e n t l y to harvest the crop. Part I I I Table 13 Mcintosh on Eagt Mailing I Date of 1940 May 29 1941 May 16 1942 May 15 1943 May 31 1944 May 22 1945 May 21 1946 May 25 1947 June 6 1948 May 28 1949 May 21 1950 May 28 1951 May 21 1952 May 22 Average Degree Days By Month. Years 1940-1952 - Base 50°F. At Ottawa. Ontario May June 155 368 157 182 447 109 474 245 455 80 389 140 395 16 388 70 396 80 556 160 431 216 391 99 467 544 / r r 642 555 602 644 555 568 611 602 675 574 580 661 Month 516 426 490 471 637 520 42? 665 590 623 450 447 520 116 185 247 167 319 287 265 325 273 £3 192 275 Date of October Harvest Sept. 13 Sept. 1? Sept. 26 Sept. 23 Sept. 29 Sept. 28 Sept. 25 Oct.' 2 Sept. 24 Sept. 16 Sept. 19 Sept. 20 Sept. 24 Total Total No. of Degree Days Davs 117 134 144 125 140 140 133 138 129 118 124 132 135 1699 1927 1921 1823 2300 1831 1795 2006 1931 2067 1763 I826 2022 131 1916 Period begins 10 days before f u l l bloom. ON ! o . .. 1940 1941 1942 i & 1945 1946 194? 1948 1949 1950 1951 1952 Date of f W pipoffi May 29 May 16 May 15 May 31 May 22 May 21 May 25 June 6 May 28 May 21 May 28 May 21 May 22 Table H (Continued) Degree Days By Month. Years 1940-1952 - Base 46°F. * O t t a w a . Ontario May June July 207 488 668 640 252 637 766 550 278 567 679 614 153 594 726 595 317 575 768 761 134 502 679 644 205 515 692 551 30 508 735 789 114 516 726 714 158 676 799 747 216 551 698 574 292 511 704 571 171 587 785 644 At Month August September 164 248 339 247 414 384 357 412 364 201 212 268 367 Date of October Harvest Sept. 13 Sept. 1? Sept. 26 Sept. 23 Sept. 29 Sept. 28 Sept. 25 5 Oct. 2 Sept. 24 Sept. 16 Sept. 19 Sept. 20 Sept. 24 Total Total No. of Degree Days Days 117 134 144 125 140 140 133 138 129 118 124 132 135 2167 24-53 2477 2315 2835 2343 2320 2479 2434 2581 2251 2346 2554 Average 131 2427 ON ! Table 13 (Continued) Degree Days By Month, Years 1940-1952 - Base 4-2°F. At Ottawa. Ontario. Moflth, Date of F u l l Bloom May June July August September Total Total Date of No. of Degree October Harvest Days Days 194-0 May 29 259 608 194-1 May 16 355 757 194-2 May 15 384- 687 194-3 May 31 197 714-194^ May 22 393 695 194-5 May 21 206 622 194-6 May 25 276 635 194-7 June 6 4-6 628 194-8 May 28 170 636 194-9 May 21 24-0 796 1950 May 28 272 671 1951 May 21 373 631 1952 May 22 251 707 Average 792 764- 212 890 674- 312 803 738 4-38 850 719 334-892 885 516 803 768 4-89 816 675 4-53 859 913 •507 850 838 4-56 923 871 261 822 698 285 828 695 3 W 909 768 4-59 Sept. 13 Sept. 17 Sept. 26 Sept. 23 Sept. 29 Sept; 28 Sept. 25 Oct. 2 Sept. 24* Sept. 16 Sept. 19 Sept. 20 Sept. 24-117 134-1W 125 14-0 14-0 133 138 129 118 124-132 135 2635 2988 3050 2814-3381 2888 284*9 2962 2950 274-8 2871 3094-131 294-8 ON ro 194-0 194-1 194-2 194-7 194-8 194-9 1950 1951 1952 Table H (Continued) Degree Days By Month, Years 194-0-1952 - Base 34-°F. At Ottawa. Ontario Month Date of F u l l Bloom May June July August September Total Total Date of No. of Degree October; Harvest Days Days May 29 May 16 May 15 May 31 May 22 May 21 May 25 June 6 May 28 May 21 May 28 May 21 May 22 IP 563 600 285 551 373 4-06 78 282 84-8 997 927 875 868 876 4-08 1036 384- 911 54-1 871 4-11 94-7 104-0 1138 1051 1098 1140 1051 1064-1107 1098 1171 1070 1076 1157 1012 922 986 967 1133 1016 923 1161 1086 1119 94-6 94-3 1016 308 ¥+0 638 510 735 705 64-5 ?4o 64-0 381 4-29 4-96 64-3 22 Sept. 13 Sept. 17 Sept. 26 Sept. 23 Sept. 29 Sept. 28 Sept. 25 Oct. 2 Sept. 24= Sept. 16 Sept. 19 Sept. 20 Sept. 24-117 134-J#f 125 l4o 14-0 133 138 129 118 124-132 135 3571 4-060 4-202 3814-44-94-4-007 3913 3976 3982 4115 374-0 3927 4-174-Average 131 3998 ON I 64-. The foregoing table shows that i n the t h i r t e e n year period 194-0-1952 at Ottawa some v a r i a t i o n was noted from year to year In the t o t a l number of degree days and also i n the number of degree days f o r the same month i n d i f f e r e n t years. Table 14-The Deviation of the Total number of Degree Days From The Average for S i x Base Temperatures at Ottawa, Years 194-0-1952  Base Base Base Base ig°F_. 4 | ^ . 4-2°F. 34-°F. -217 -260 -313 -4-27 11 26 4o 62 5 50 102 204--93 -112 -13^ -184-384- 408 4-33 -60 4-96 -85 -84- 9 -121 -107 -99 •^85 90 52 14- -22 15 7 2 -16 151 15»+ I * * 117 -153 -176 -200 -258 -96 -81 -7? -71 106 127 14-6 176 Series Series K L -217 -24-9 11 -6 5 17 -93 -93 384- 399 -92 -75 -121 -109 90 101 15 26 151 139 -153 -169 -90 -94-106 118 Year 1940 194-1 194-2 194-3 194^ 194-5 19^6 194-7 194-8 194-9 1950 1951 1952 Series K - Base temperature of 50°F. i n May, 4-2°F. In June, 34-°F. i n July and August and 50°F. i n September. Series L - Base temperature of 50°F. i n May, H2°F. i n June, 34-°F. i n July and August and U ^ F . ' i n September. The deviation from the t h i r t e e n year average f o r each of the s i x base temperatures given i n Table 14- shows that no one base temperature was consistently better than any other. The base 4-2°F. occupied a medial p o s i t i o n while 34-°F. seemed to be l e a s t s u i t a b l e . Series K except f o r the 65. year 1945 was exactly the same as base 50°P. Small deviations from the average were the rule f o r year rather than f o r base temperature. Extreme years were selected and the range i n degree days between those years were calculated by month as i n Table 15 below. Table 1? The Range In Total Degree Days Between Extreme Years By Month During the Period 1940-1952 at Ottawa Base Temperature 50°F. 46°F. 42°F. 34°F. Extreme Extreme Extreme Extreme Month Range Years Range Years Range Years Range Years May 229 287 338 522 1942, 1947 June 188 1940, 1949 188 1940. 1949 188 1940, 1949 188 1940, 1949 July 131 1940, 1949 131 131 1940. 1949 131 August 239 1941. 1947 239 1941, 1947 239 1941. 1947 239 1941, 1947 Septem-ber 209 " ^ 7 250 l9%> 304 1940, 1944 432 1940, 1947 The above table shows that there was some f l u c t u a t i o n i n the extreme years for May and September and also shows the uneven range with decreasing base temperatures. Besides temperature fluctuations there was the factor of an i n d e f i n i t e * very variable number of days i n May and September 66. on which degree day determinations were made. The years I9J+9 and 1940 were extremes f o r the months of June and July but 1947 and 1941 were the extreme years f o r August. The range i n June (188 degree days) was the same f o r a l l base temperatures. The same was true of July and August except that the range was 131 and 239 degree days r e s p e c t i v e l y . These data indicated that the average d a i l y temperature did not drop below 50°P. i n June, July and August at Ottawa f o r those years. May and September were c r i t i c a l months i n the s e l e c t i o n of base temperatures. Table 16 A Comparison of the Total Degree Day Averages Based on a Five Year Period and on a Thirteen Year Period at Ottawa. Four Base Temperatures Base Temperature Base Temperature 34°F.' 42°F. 5 Year Av. 13 Year Av. 5 Year Av. 13 Year Av. 3988 3998 2951 2948 Base Temperature Base Temperature 46°F. 50°F. 5 Year Av.' 13 Year Av. 5 Year Av. 13 Year Av. 2433 2427 1922 1916 The f i v e year average f o r the t o t a l degree days as i s shown i n Table 16 d i f f e r e d but s l i g h t l y from the t h i r t e e n year average f o r a l l base temperatures. The greatest difference was shown using a base of 34°F. but even here the difference was only ten degree days. 67. Table 17 Average Monthly Temperature f o r Years 1948-1951 A-h Syrmmerland Month 1948 1942 1250. 222k Average May 55.5 59.6 55.1 58.8 57.3 June 67.9 62.5 65.3 63.8 64.9 July 66.5 68.2 70.4 71.2 69.1 August 64.5 66.8 68.7 68.6 67.2 September 58.1 60.1 62.7 61.6 60.6 Average 62.5 63.^ 64.4 64.8 63.8 Table 17 indicates that the average monthly temperature for the growing season or phenological period at Summerland, B. C , varied from 57.3°F« i n May.to 69.1°F. i n J u l y . Unlike the temperature at Ottawa the month of July was not the warmest month i n a l l years. In 1948 the average temperature i n June exceeded that of the month of J u l y . However, the average temperature f o r July was higher than any other month for the years observed. The grand average was 63.8°F., s l i g h t l y higher than that of Ottawa. Table £8 Mcintosh on East M a i l i n g I Degree Days By Month, Years 1940, 1941, 1946-1952 - Base 50°F. ; At Summerland. B r i t i s h Columbia Date of 1941 1946 1947 1950 1951 Average F u l l Bloom A p r i l May June A p r i l 3 0 39 2 8 9 532 A p r i l 2 5 103 2 2 8 4 1 5 May 7 5 313 316 May 1 57 3 2 9 360 May 21 177 537 May 8 316 3 7 5 May 19 177 4 5 8 May 12 271 4 1 5 May 10 242 3 3 7 Month 6 9 2 7 3 1 5 8 5 573 51-2 564 633 656 588 586 584 4 9 4 4 5 0 520 58© 576 591 Date of September Harvest 2 6 9 119 283 150 253 216 3 8 8 222 2 2 3 Sept. 15 Sept. 1 5 Sept. 27 Sept. 19 Sept. 28 Sept. 22 Sept. 2 9 Sept. 17 Sept. 2 0 Total No. of Days 148 153 153 147 143 138 142 146 Tot a l Degree Days 2 4 0 7 2180 2 0 6 9 1963 1929 1991 2 2 3 6 2140 1981 2 1 0 0 Period begins 10 days before F u l l Bloom. ON 1 0 0 Table 18 (Continued) Degree Days By Month, Years 1940, 1941 , 1946-1952 - Base 4 6 ° P . At Summerland. B r i t i s h Columbia  Month Total T o t a l Date of _ _ Date of No. of Degree Tuly August September Harvest Days Days 816 710 3 2 5 Sept. 1 5 148 2 9 8 9 1941 A p r i l 2 5 160 3 5 1 535 8 5 5 708 175 Sept. 15 153 2 7 8 4 1946 May 7 14 435 4 3 6 7 0 9 6 9 1 3 8 7 Sept. 27 153 2 6 7 2 1947 May 1 95 4 5 3 480 6 9 7 618 218 Sept. 19 151 2 5 6 l F u l l Bloom A p r i l May June A p r i l 3 0 78 4 0 8 652   0 1   7    1    May 21 2 5 8 657 May 8 5 4 2 6 4 9 5 May 19 2 6 5 578 May 12 3 9 1 May 10 353 4 5 6 574 3 55 Sept. 28 140 248© 1949     6 8 8 644 3 0 0 Sept. 22 147 2 5 5 8 1950  19   7 5 7 704 4 9 9 Sept. 2 9 143 2 8 0 3 1951  12  535 7 8 0 700 286 Sept.' 17 138 2 6 9 2 1952  10   712 715 2 9 9 Sept. 20 142 2 5 3 5 Average 146 2 6 7 5 ON NO Table 18' (Continued) Degree Days By Month, Years 1940, 1941, 1946-1952 - Base 42°F. At Summerland. B r i t i s h Columbia Date of F u l l Bloom A p r i l May June A p r i l 30 120 532 772 A p r i l 25 224 475 655 May 7 26 559 556 May 1 135 577 600 May 21 342 777 May 8 13 549 615 May 19 356 698 May 12 ,511 655 May 10 476 576 Mo&tii 940 979 833 821 Total Total Date of No. of Degree Harvest Days Days 834 832 815 742 698 768 828 824 839 381 231 491 290 463 384 611 350 375 Sept. 15 Sept. 15 Sept. 27 Sept. 19 Sept. 28 Sept. 22 Sept. 29 Sept. 17 Sept. 20 148 153 153 151 140 147 143 13o 142 3579 3396 3280 3165 3040 3141 3374 3244 3102 Average 146 3258 -s3 O Table 18 (Continued) Degree Days By Month, Years 1940, 1941, 1946-1952 - Base 34°F. At SummerlandT B r i t i s h Columbia Month, Date of 1940 A p r i l 30 208 780 1012 1188 1082 493 1941 A p r i l 25 352 723 895 1227 1080 343 1946 May 7 50 807 796 1081 IO63 699 1947 May 1 215 825 840 IO69 990 434 1948 May 21 510 1017 1008 946 679 1949 May 8 29 797 855 1060 1016 552 1950 May 19 540 938 1129 1076 835 1951 May 12 751 895 1152 1072 478 1952 May 10 724 816 1084 1087 527 Average Total Total Date 1 of No. of Degree Harvest Days... Sept* 15 148 4-763 Sept* 15- 153 4620 Sept* 27 153 4496 Sept* 15 151 4-373 Sept* 28 140 147 4160 Sept* 22 4309 Sept* 29 143 Sept* 17 138 4348 Sept* 20 142 4238 146 4425 - s i H 72. Table 18 shows that the v a r i a t i o n i n t o t a l degree days f o r a nine year period at Summerland was s i m i l a r to that shown i n the th i r t e e n years at Ottawa (Table 13). The four base temperatures 50°F., 46°F., 42°F. and 34°F., a l l showed variations from year to year. Table jL? The Deviation of the Total Number of Degree Days Prom the Average For Six Base Temperatures at Summerland. B.C.. Years 1940-1941. 1946-19*2 Jeax Base Base Base 42°F. Base 34**F. Series Series „ K.. 1940 307 314 321 338 308 283 1941 80 109 138 195 81 56 1946 -31 -3 22 71 -30 -7 1947 -137 -114 -93 -52 -136 -149 1948 -171 -195 -218 -265 -170 -149 1949 -109 -117 117 -116 -108 -105 1950 136 128 116 93 137 167 1951 40 17 -14 -77 41 24 1952 -119 -140 -156 -187 -119 -124 Series K and L as i n Table 14 Table 19 shows that again no one base temperature appeared to be e n t i r e l y s a t i s f a c t o r y . Series K was almost the same as the base temperature of 50°F. On the whole Series L was better than Series K or the base temperature of 50°F. and may have been s l i g h t l y better than the continuous 7 3 . base temperatures of 46°F. and 42°F. Series L had the smallest deviation from the i n d i v i d u a l yearly average f o r 56 per cent of the years included i n the study. Calculations based on a base temperature of 42°?. shoved the same medial tendency as with the Ottawa data, and 34°F. gave the largest deviations from the average. Table 20 The Range i n Total Degree Days Between Extreme Years By Month i n the Years 1940, 194-1, 1946-1952, At SnTtwnerland. B. C. Base Temperature 50 °F . 46°F.' 42°F. 34°F. Month Ranee Extreme Years Extreme Jears Bantf* Extreme Years ; Ranee Extreme - Years,, May 152 1947, 1948 195 1947,, 1948 235 I947, 1948 315 . June 221 1946, 1948 221 1948 221 1948 221- 1946, 1§48 July 219 1941.; 1948 219 1941, 1948 219 1941, 1948 219 1941, 1948 August 141 1948, 1952 141 1948, 1952 141 1948, 1952 141 1948, 1952 Septem-ber • 269 1941, 1950 324 1941, 1950 380 1941, 1950 492 1941, 1950 The range i n t o t a l degree days between extreme r years In Table 20 shows s i m i l a r relationships f o r Summerland as were apparent at Ottawa. That i s , there was the same f l u c t u a t i o n i n May and September while the months of June, 74. July and August had the same range i n each month f o r a l l base temperatures. The range f o r June was 221 degree days, that f o r July 219 degree days and 141 degree days f o r August, The range f o r June and July was much greater at Summerland than at Ottawa, but the reverse was true f o r the month of August, The greatest difference between extreme years occurred i n June at Summerland and i n August at Ottawa, A comparison of the t o t a l number of degree days required to mature Mcintosh on East Mailing I at Ottawa and at Summerland as shown i n Table 21 indicates that except f o r four instances using a base of 50°F, and two instances using a base temperature of 46°F,, the t o t a l number of degree days at Summerland exceeded that at Ottawa, The average difference i n the t o t a l degree days between locations decreased as the base temperature was r a i s e d , but showed extensive v a r i a t i o n s even w i t h i n base temperatures. For instance, i n 1948 with a base temperature of 50°F,, the difference i n t o t a l degree days between Ottawa and Summerland was only two degree days. In 1940 t h i s difference f or the same base temperature was 708 degree days. Table 21 Variety Mcintosh on East Mailing I Comparison of the Total Number of Degree Days Required to Mature Apples at Summerland and at Ottawa by Base Temperature and Year Base Temperature 50°P. Difference h6°F. Difference 4 2 ° F . Difference 3 4 ° F . Difference Base Temperature 1940 S. Oj, 2407 1699 708 2989 2167 822 3579 2635 944 4763 3571 1192 1949 S* Oj, 1941 S. 0 * 2180 1927 253 2784 2453 331 3396 2988 408 4620-4o6o 560 1950 , 1946 Sj 0,. 1947 S« 0,, 2069 1795 274 2672 2320 352 3280 2849 431 4496 3913 583 1951 , & Qji 1963 2006 -43 2561 2479 82 3165 2962 203 4373 3976 397 1952 S* & 1948 S« 0 , 1929 1931 -2 2480 2434 46 3040 2950 95 4160 3982 178 Average Difference 50 °F . Difference 1991 2067 -76 2236 1763 473 2140 I836 304 1981 2022 -41 243 46°F. Difference 2558 2581 -23 2803 2251 552 2692 2346 346 2535 2554 -19 286 42°F. Difference 3141 3091 50 3374 2748 626 3244 2871 373 3102 3094 8 348 34°F. Difference 4309 4115 194 4518 3740 778 4348 3927 421 4238 4174 64 485 ana Torn. Hunts* or Deatce D * n BY Yfais AT OTTAWA A*/O Suriritni»no LcatrfO ivto '111 itqt >f93 i**q >9v >*fi /fir 19*9 >9so /<??/ ,tfi Figure I I I Total Number of Degree Days by Years at Ottawa and Summerland, Base Temperature 50°F. v 3 Figure IV Total Number of Degree Days by Years at Ottawa and Summerland, 34 0F. 76. Table 22 Total Number of Days i n Phenological Period For Years Indicated at Ottawa, Ontario, and Summerland, B.C., With the Deviation From the Average Ottawa. Ontario" SnTnmp;p;i*inaT B. C. Deviation Deviation Year No. of Days From Average No. of Days From Average 1940 117 14 148 2 194-1 134 3 153 7 1942 144 1§ 1 * 3 125 6 1944 140 9 1945 140 9 1946 133 2 153 7 194-7 138 7 151 5 1948 129 2 140 6 1949 118 13 147 1 1950 124 7 143 3 1951 132 1 138 8 1952 135 4 142 4 Average 131 7 146 5 Period begins 10 days before f u l l bloom On the average i t took longer to mature the f r u i t at Summerland than at Ottawa when a comparison between the t o t a l number of days i n the phenological period at Ottawa and the t o t a l number of days at Summerland i s made. Individual years deviated from the average by as much as fourteen days at Ottawa while at Summerland the greatest deviation from the average was only eight days. The average deviation f or thirteen years at Ottawa was seven days; that at Summerland for nine years only f i v e days. Jor/tt. NoiacK or Ours ve PufotociCAL finii°o AT OTTAWA AKO *r SuHM*ti'ite ( i I I « latino I . , OTTAWA » • SunncAiAnD I I lano ,111 ifil iftf l»9C /tft 1991 /99t 1999 1*10 HSI lati yaaa. Figure V Total Number of Days i n the Phenological Period at Ottawa and at Summerland Seedling Variety 0-277 Increase i n Diameter of Apples on Spurs on Dates Indicated Measured i n Centimetres ; ' Date Sour 1A Spur IB Sour IC Spur 2A Spur "\k Spur 4A Spur 4B Average June 5 .22 .23 .20 .23 .18 .07 .12 .1785 June 8 .24 .20 .21 .21 .33 .25 .25 .2414 June 10 .18 .19 .27 .28 .10 .22 .16 .21 .2071 June 12 .15 .13 .13 .14 .10 .13 .1343 June 15 .32 .28 .27 .31 .29 .23 .26 .2800 June 17 .23 .14 .21 .25 •22 .19 .22 .24 .2085 June 19 .20 .18 .28 .23 .20 .21 •2200 June 22 .24 .28 .39 •26 .13 .16 .18 .2342 June 24 .07 .24 .18 .10 .19 .07 .16 .26 • 3 f .26 .1700 June 26 .10 .10 .20 .16 .1742 June 29 .17 .27 .24 .17 .20 .18 .2085 July 1 .07 .06 .14 .08 .14 .11 .10 .13 .1100 July 3 .13 .15 .17 .13 .15 .1343 July 6 .16 .16 .15 .14 .17 .18 .20 .1657 July 8 .07 .09 .11 .14 .09 .10 .05 .0929 July 10 .06 .08 .06 •15 .09 .15 .10 .11 .0929 July 13 .10 .17 •20 .17 A? •V .1557 July 15 .12 .09 .13 •15 .10 .14 .14 .1243 July 17 .09 .14 .03 .02 •P7 ,07 .07 ,07 .0600 July 20 .19 .21 .19 .05 .20 .04 .23 .05 .20 .06 .1943 July 22 .00 .05 •00 .0357 July 24 .11 .14 .16 .12 .11 .10 .10 .1200 Average Growth Per Day .0893 .0805 .1036 .0672 .0933 .1043 .1100 .0781 .0850 .0871 .0695 .0550 .0672 .0552 .0465 .0465 .0519 .0622 .0300 .0648 .0179 .0600 NI NI The i n v e s t i g a t i o n into the r e l a t i o n between increase i n size and temperature using the Ottawa seedling 0-277 as study medium and i l l u s t r a t e d i n Table 23 shows that the greatest increase i n growth per day f o r seven apples took place from the time the measurements were started u n t i l about June 19th# The greatest average increase was eleven hundredths of a centimetre and was recorded on June 19th# From that date growth decreased s l i g h t l y but f a i r l y r e g u l a r l y u n t i l July 1st, from whence the growth fluctuated around the ,05 centimetre mark f o r the remainder of the season. 1 79. Table 24 Average Growth Per Day and Average Temperature Per Day As Recorded on 0-277 at Ottawa i n 1953 (Seven Apples) Average Growth Average Temperature Date Per Day For Same Period (cm.) ~ °F. ~-~" June 3 June 5 .09 53.4 June 8 .08 64,1 June 10 .10 62.7 June 12 .07 57.7 June 15 .09 59.4 June 17 .10 65.1 June 19 .11 69.2 June 22 .08 76.2 June 24 .09 66.6 June 26 .09 63.0 June 29 .07 71.0 J u l y 1 .06 68.1 July 3 .07 72,4 J u l y 6 .06 64.5 J u l y 8 .05 67.3 July 10 .05 58,9 July 13 .05 64.3 July 15 .06 68.5 J u l y 17 .03 75,6 July 20 .06 79.3 July 22 .02 78.0 July 24 .06 75.5 An examination of the average growth per day f o r seven apples together with the average temperature f o r the same period of time as i n Table 24 reveals no v i s i b l e c o r r e l a t i o n . When the co r r e l a t i o n was calculated f o r these data using a method outlined by Goulden (23) the c o e f f i c i e n t of c o r r e l a t i o n was found to be - . 4 0 5 . The t test of significance gave a t value of 1.98 which i s less than the required t s 2.09 f o r H a 20 at P s . 0 5 . Therefore the 80. c o e f f i c i e n t of co r r e l a t i o n was not s i g n i f i c a n t mathematically, Table 25 Variety Mcintosh on Bast Mailing I Average Increase i n Size of Apples Per Tree on Dates Indicated Measured i n Centimetres Tree 1 Tree 2 Tree ^ Average June 24 June 26 .24 .19 .24 ,2233 .2600 June 29 .24 •29 .15 •25 July 1 •13 .14 .1460 July 3 ,15 •19 .16 .1667 July 6 •19 .22 .20 •2033 July 8 ,13 •17 ,17 .1567 July 10 .14 .14 •12 •25 ,1333 July 13 .20 .24 .2300 July 15 .12 .12 ,1233 July 17 .09 .16 .10 •09 •0933 .1633 July 20 .16 .17 July 22 .05 .06 •05 •0533 July 24 ,13 ,13 .12 .1267 July 27 .20 .22 .18 •2000 .0833 July 29 . 0 ? .09 .09 July 31 .06 .07 .05 .0600 August 3 .07 .10 . 0 9 .0867 August 5 .10 .13 .11 .1133 .0967 August 7 .11 .11 .07 August 10 .09 .14 .13 .1200 August 12 •13 .16 .23 .08 .1733 August 14 .12 .10 .1000 August 17 .10 .12 .12 .1133 August 19 •09 .07 • 08 .0800 August 21 •07 .09 .07 .0767 August 24 .09 .10 •09 •0933 .0667 August 26 .06 •07 .07 August 28 .04 .07 .06 .0567 August 31 •05 .05 •03 .0433 September 2 .02 .02 .03 .0233 September 4 .02 .03 .04 .0333 September 7 •05 •09 .05 .0633 September 9 .05 .05 .07 .0567 September 11 .05 .05 ,05 .0500 September 14 .05 •06 •07 .0600 September 16 .04 .05 .05^ .0467 September 18 .02 .06 .03 .0367 Average Growth Per Day .1117 .0867 .0700 .0834 .0678 .0784 .0667 .0767 .0617 .0467 •0544 .0267 .0634 .0667 .0417 .0300 .0289 .0484 .0460 .0867 .0378 .0400 .0384 ,0311 •0334 .0284 .0144 .0117 .0167 .0211 .0284 .0250 .0200 .0234 .0184 81. Table 25 (Continued) Average Growth Date Tree 1 Tree 2 Tree 3 Average' Per Day September 21 .06 .10 .08 .0800 .0267 September 23 .02 .03 .04 .0300 .0150 The above table shows i r r e g u l a r growth up to August 12, from whence the growth rate begins to decline. The d a i l y increase i n size of the apples was very small a f t e r August 28. The greatest growth was recorded on June 26. Table 26 Average Apple Growth Per Day and Average Temperature Per Day As Recorded on Mcintosh on East Mailing I at Ottawa i n 1953 (Three Trees. Twelve Apples) Average Temperature Date Average Growth Per Day For Same Period 24 (cm.) Degrees F. June — • June 26 .11 63 June 29 .09 71 July 1 .07 69 July 3 .08 73 July 6 .07 .08 65 July 8 68 July 10 .07 P July 13 .08 .06 65 July 15 6 I July 17 .05 76 July 20 .05 79 July 22 .03 76 July 24 .06 76 July 27 ,07 .04 63 July 29 72 July 31 .03 ?? August 3 .of 64 August 5 .06 60 August 7 .05 ¥ August 10 .04 67 August 12 .09 " 67. 82. Table 26 (Continued) Date August 14 August 17 August 19 August 21 August 24 August 26 August 28 August 31 September 2 September 4 September 7 September 9 September 11 September lh September 16 September 18 September 21 September 23 Average Growth Per Day (can.) .05 .04 .04 .04 •03 .03 .03 .01 .01 .02 .02 .03 .03 .02 .02 .02 .03 .02 Average Temperature For Same Period Degrees F. 71 68 60 V 65 72 76 82 76 77 70 61 54 60 49 52 58 52 A v i s u a l study of the gro\rth and temperature data f o r the variety Mcintosh on East Mailing I shows very l i t t l e c o r r e l a t i o n * This observation was v e r i f i e d when the co r r e l a t i o n c o e f f i c i e n t was calculated a f t e r Goulden (23), and found to be 0.032. The t test of significance gave a v t value of 0.20 which i s much less than the required t ; 2.03 f o r N = 37 at P s . 0 5 . The c o e f f i c i e n t of co r r e l a t i o n was therefore not s i g n i f i c a n t , i n d i c a t i n g no rel a t i o n s h i p between average temperature and growth, at le a s t f o r these data as presented here. 83 Discussion There are obviously three important considerations i n the science of phenology and i t s p r a c t i c a l a p p l i c a t i o n with respect to /the c a l c u l a t i o n of degree days, or the accumulation of heat units which w i l l permit the prediction of harvest maturity of the f r u i t of the apple. These considerations are: the date at which the phenological period w i l l begin, the base or unit temperatures to be employed and the maturity date of the f r u i t . I t would appear that i n the prediction of harvest maturity of the f r u i t s of perennial plants such as the apple, Malus pumil;a« ( M i l l . ) , less precision may be obtained than has been experienced with vegetable crops. In the annual plants, i n which category vegetables are most generally placed, there i s not the same degree of d i f f i c u l t y experienced i n the s e l e c t i o n of a date i n which to begin the phenological period because the date of sowing or the date of emergence generally w i l l s u f f i c e . In perennial crops t h i s aspect,of the problem i s much more complicated. In these plants the two dominant phases of plant growth, vegetative and reproductive, are very closely related over a time i n t e r v a l which may begin during the spring or early summer of the year preceding the maturation and harvest of the f r u i t ' . Bud d i f f e r e n t i a t i o n i s an example of t h i s sort of phenomenon. Further complications may a r i s e due to the 84, part played by cl i m a t i c environment during the rest and dormancy periods, the l a t t e r usually l i m i t e d by winter temperatures (19> 27, 36); the former may be i n i t i a t e d some time before the cooler temperatures begin and may be broken any time upon completion of the required accumulation of low temperatures* I t i s jus t possible that the phenological period should begin at some time during the year preceding that of the year of harvest. Undoubtedly t h i s may account, at l e a s t i n part, for the v a r i a b i l i t y i n t o t a l degree days found by using the date of f i r s t bloom as the beginning of the phenological period. The minimum and optimum temperatures at which plants grow best i s not easy to ascertain f o r according to S c h i l l e t t e r & Rickey (52), i n t e r n a l and imperceptable growth processes such as the development of f l o r a l parts and the thickening of c e l l walls may occur even during the dormancy period of the tree. Therefore c e r t a i n i n t e r n a l changes are undoubtedly taking place at the very low temperatures which prohibit outward manifestations of growth. However, i t i s generally agreed (1, 4 3 , 40, 30) that temperatures from 42°F, to 50°F, are most desirable f or ordinary growth processes. When the extremes of t h i s temperature range are used i n ca l c u l a t i n g t o t a l degree days as i n Table 1(a) the same trend i s observed i n both base temperatures with less yearly v a r i a b i l i t y i n t o t a l degree days at the higher base 85. temperature due, doubtless, to the f a c t that average temperatures are less variable above 50°F, The t h i r d consideration In phenological studies i s an accurate, reproducible Indices of f r u i t maturity. In the apple no e n t i r e l y s a t i s f a c t o r y index of maturity has yet been devised (24), Harvesting dates are therefore somewhat haphazard, f o r i n addition to the lack of a good maturity index, harvesting may be dictated by the demands of the consumer or by the size of the labor force at harvest. That i s , an apple crop may be picked immature because of a good current demand for apples or on the other hand the harvest period may be extended beyond optimum maturity i f few pickers are available for the work of harvesting. However, as the apples under in v e s t i g a t i o n i n t h i s paper were harvested on a research farm only the factors of labor and maturity could contribute to the v a r i a b i l i t y of the t o t a l degree days. In t h i s study the maturity index as suggested by the Low Temperature Storage Research Section of the D i v i s i o n of Horticulture resulted i n a v a r i a t i o n of 458 degree days (base temperature, 42°F,) In the v a r i e t y Mcintosh between the years 1949 and 1950 while the ordinary harvest dates as recorded from the f i e l d resulted i n a v a r i a t i o n of only 400 degree days under the same conditions. Since there cannot be an error of more than f i v e days i n apple maturity prediction dates or the f r u i t w i l l 86 have advanced to an unsatisfactory stage of maturity (24) and since the average number of degree days f o r September at Ottawa i s sixteen f o r the years examined (Table 1(b)) a v a r i a t i o n of over 400 degree days would r e s u l t i n a v a r i a t i o n of twenty-five days, considerably i n excess of that which can be permitted i n prediction work* S i m i l a r l y , assuming each day i n September has an average of sixteen degree days, the difference of 458 degree days indicates a possible difference of approximately twenty-eight days i n the harvest dates between the years 1949 and 1950. But the employment of the average number of degree days f o r the four year period as a c r i t e r i o n of harvest date reduces the deviation of the harvest date i n 1950 to f i f t e e n days and that of the year 1949 to fourteen days (Table 2 ) , The t o t a l hours of sunshine as i n Table 2 bears l i t t l e r e l a t i o n s h i p to the t o t a l number of degree days* The highest accumulation of 1070*3 hours of sunshine and the greatest number of degree days was l i s t e d i n the year 1949« But i n 1951 there were only 920*2 hours of sunshine with a t o t a l of 2945 degree days, only s l i g h t l y higher than the 2902 degree days l i s t e d f o r the year 1948 which accumulated a high of 1006*8 hours of sunshine, A s i m i l a r r e l a t i o n s h i p or lack of r e l a t i o n s h i p i s shown between the t o t a l hours of sunshine and the number of days i n the phenological period* The season was longest i n 1951 with a t o t a l of 132 days and 87. a r e l a t i v e l y low accumulation of sunshine, while i n 1S&-9 the season consisted of 130 days but i n t h i s year there accumulated more hours of sunshine than i n any of the other three years l i s t e d . The number of days i n the phenological period appears to be the best c r i t e r i o n to use i n prediction work from the data i n Table 2, which confirms the observations of Haller (24), The difference i n the number of days between the extreme years of 1949 and 1950 was only s i x days and the number of days i n the growing season f o r these years varied from the average by only three days. The greatest deviation from the average was i n 1951 when the number of days In the season was f i v e days more than the average. Using the number of days i n the season may just come with the range of precision desired f o r prediction purposes according to the data i n Table 2 but information gained i n examining a longer time i n t e r v a l rather discourages t h i s p o s s i b i l i t y (Please see Table 22). From Table 1(a) i t would appear that since there i s a general increase i n the t o t a l number of degree days required to mature apples from early to l a t e v a r i e t i e s , a simple c l a s s i f i c a t i o n may be drawn up using t o t a l degree days from blooming period to harvest as a c r i t e r i o n of maturity. Assuming a base temperature of «+2°F, the c l a s s i f i c a t i o n could be arranged i n t o three broad groups, one being from a t o t a l number of degree days of 2000 to that of 2700 degree days. Another group might be from 2700 to 3100 degree days and the l a s t group could include those v a r i e t i e s ripening with an accumulation of over 3100 degree days* The extremes of the c l a s s i f i c a t i o n represent the very early v a r i e t i e s as Melba and the very l a t e as Niobe. The intermediate c l a s s i f i c a t i o n of 2700 - 3100 degree days would include many of the better v a r i e t i e s grown at the Central Experimental Farm, that i s , v a r i e t i e s as Mcintosh, Linda, Edgar, Fameuse, Lawfam and Sandow. From the data obtained i n t h i s Investigation i t would appear that Fameuse matured a f t e r Lawfam* A c t u a l l y , the Fameuse va r i e t y may mature a l i t t l e e a r l i e r than Lawfam* However, f o r a l l p r a c t i c a l purposes they may be said to mature at the same time as there i s considerable f l u c t u a t i o n from year to year between v a r i e t i e s and within v a r i e t i e s * The success or f a i l u r e of a degree day c l a s s i f i c a -t i o n as suggested above would depend very l a r g e l y upon the accuracy with which the phenological period can be determined* The data from the Record Section with respect to dates of harvest were used i n a l l calculations subsequent to Table 2, since as was noted e a r l i e r i n t h i s discussion, the data from the Record Section were as good as or better than those from the Low Temperature Storage Research Section* The f a c t that data from the Record Section were more complete 89. as w e l l as more accessible also influenced that decision. This then e f f e c t i v e l y takes care of the l a s t consideration i n phenological i n v e s t i g a t i o n s , that of f r u i t maturity date mentioned e a r l i e r and leaves the way clear f or a study of the remaining two aspects of phenological applications; namely, the i n i t i a t i o n of the period and the temperature bases to be employed. These should be arranged i n such a manner that greater precision i n yearly t o t a l degree days i s achieved. An examination of the phenological data f o r the years 1948-1952 at Ottawa i n Table 4 indicates that the years 1950 and 1952 are extreme years of low and high t o t a l degree days respectively. This makes these years I d e a l l y suited f o r use as c r i t i c a l years upon which to t r y various combinations of temperatures through the growth period as suggested by L i l l e l a n d (3D > Tukey (59) and Ellenwood (20). I t i s not unreasonable to conclude that using a single base temperature throughout the growing period may introduce a source of error as the tree may require d i f f e r e n t optimum temperatures f o r optimum growth during the various phases r e l a t i n g to the maturation of f r u i t . In Table 3 several combinations of base temperatures for each month of the growing season as w e l l as a further refinement, namely, that of s t a r t i n g the phenological period from f u l l bloom rather than from f i r s t 90 bloom, did not decrease the v a r i a t i o n i n t o t a l degree days appreciably. The Series known as F i s equally as good as Series G and both are better than a l l the other combinations t r i e d . Actually the only temperature base i n Series F that may be said to be d i f f e r e n t from any i n Series G was 42°F. i n June. Since the average temperature i n July and August at Ottawa ra r e l y goes below 50°F., any base temperature selected below that would r e s u l t i n a constant d i f f e r i n g only i n magnitude with the base temperature selected. That there i s l i t t l e to choose between the combination of base temperatures, Series F and that of Series G i s further demonstrated i n Table 4 where the t o t a l degree days are l i s t e d f o r the years 1948-1952 under the base temperatures of 34°F., 38°F., 42°F., 50°F. and Series F. Here the deviation from tie average i s exactly the same f o r Series F and the base temperature of 50°F. (Series G). Extreme v a r i a t i o n i n the t o t a l number of degree days i s noted from year to year although there i s a marked increase i n p r e cision when the deviation of each year's t o t a l i s taken from the f i v e year average. The precision gained by the use of the date of f u l l bloom, rather than that of f i r s t bloom as the Period s t a r t i n g point i s doubtful. There was a difference of 400 degree days between the t o t a l degree days i n the years 1949 and 1950 i n Table 1(a) with the use of a 42°F. base temperature and the date of f i r s t bloom; while 91. using f u l l bloom t h i s difference under the same conditions was 415 degree days. In a s i m i l a r manner, for the same conditions except that a base temperature of 50°P. was used, the difference i n t o t a l degree days changed from 359 using f i r s t bloom to 375 using f u l l bloom. When the phenological period i s extended to include the period ten days before f u l l bloom there i s a marked increase i n precisi o n . For instance, with a base temperature of 34°F. and s t a r t i n g from f u l l bloom i n the year 1950, there was a deviation from the average of 319 degree days; but when the period was extended ten days the deviation from the average was only 248 degree days. Similar increases i n precision are observable with the other base temperatures employed. I t would appear, therefore, that considerable precision may be gained by s t a r t i n g the phenological period ten days before f u l l bloom rather than at f u l l bloom or even at f i r s t bloom. However, t h i s s t i l l does not bring the t o t a l degree day v a r i a b i l i t y to withi n the desirable eighty degree days (based on the average sixteen degree days per day found i n Table 1(b) )• In addition there are so many other aspects to phenological problems that should be examined such as: temperature (4, 44, 55» 21), l i g h t (38), the employment of the multiple of mean temperature and day length (1, 42), moisture and growth (57» 67, 54), multiple c o r r e l a t i o n of 92. pertinent f a ctors (15, 18, 53), p r o b a b i l i t y predictions based on past performances (13)j night temperature (62, 48), n u t r i t i o n (56) and plant physiological aspects (47), that I t seems prudent to examine the p o s s i b i l i t i e s , however b r i e f l y , of a few of these at l e a s t , and with the understanding that these factors w i l l i n no way detract from the main purpose of the investigation which concerns average temperature and the Heat Unit Theory i n the prediction of apple maturity. Obviously since the employment of the average temperature i n ca l c u l a t i n g degree days apparently does not re s u l t i n the necessary precision f o r prediction purposes from the data thus f a r examined i t becomes imperative to t r y other kinds of temperature i n the c a l c u l a t i o n s , f o r instance, the minimum temperature. The compilation of the number of 'X1 units as i n Table 6 using the minimum temperature with a base of 42°F. and data for the years 1948-1952 reveal that further precision may be gained by using the minimum temperature rather than the average temperature. Converting the 'X* units to a d a i l y basis s i m i l a r to that employed i n Table 1(b) for the growth period i n September i t i s found that the average •X1 units per day i s approximately 8.5 'X1 u n i t s . M u l t i p l i e d by f i v e t h i s comes to approximately 43 ,X I u n i t s . Except i n one instance the deviations from the average i n Table 6 are much larger than that figure i n d i c a t i n g that s u b s t i t u t i n g the minimum temperature f o r the average 93. temperature w i l l not give the required precision f o r prediction purposes, with respect to the data gathered i n t h i s i n v e s t i g a t i o n . Another al t e r n a t i v e to the use of average temperature i n c a l c u l a t i n g heat units may be night temperature for i t i s considered to be the l i m i t i n g factor i n plant growth (62). When the night temperature calculated a f t e r a method suggested by Went (62) i s substituted f or the average temperature i n c a l c u l a t i n g heat units the r e s u l t i n g units may be designated as being 'Night 1 units to d i f f e r e n t i a t e them from the degree days found i n the ordinary way. That i s , the same method Is employed i n accumulating 'Night' units as i n the standard degree procedure, except that instead of average temperature data, night temperature •averages are used. In Table 7 a comparison i s made between •Night' units using a base of 50°F. and degree days using the same base temperature, data being collected for the years 1948-1952 at Ottawa. No d i r e c t comparison can be made between the deviation of 'Night 1 units from the average and a s i m i l a r deviation f o r the degree days as the components making up the deviations are not the same. However, the -.number of 'Night' units per night f o r that part of the phenological period extending i n the month of September works out to approximately s i x u n i t s . As before t h i s number may be m u l t i p l i e d by f i v e to ascertain the permissable t o t a l 94. number of 'Night 1 units f o r maturity predictions as indicated by Haller (24). Therefore the desirable deviation should not be more than t h i r t y 'Night 1 u n i t s . An examination of the material In Table 7 shows that i n only one year, 1948, does the deviation come within the t h i r t y 'Night' u n i t l i m i t . Of course as already noted the deviation l i m i t f o r the degree day method i s eighty degree days. There does not appear to be any advantage i n the employment of night temperatures as a substitute f o r the average d a i l y temperature i n c a l c u l a t i n g heat u n i t s . Greater use of calculated night temperatures can be made when i t i s subtracted from the average temperature. The r e s u l t i n g s t a t i s t i c may be considered as a crude measure of the f l u c t u a t i o n between day and night temperatures but can be more accurately expressed as the range between maximum and minimum temperatures. The accumulated 'Y' units calculated i n th i s way are not heat units as the term has been applied throughout t h i s paper. No base or unit temperatures are involved i n the c a l c u l a t i o n s . The method i s simply a mathematical accumulation of a range of temperatures. In Table 8 the calculated average night temperature i s subtracted from the d a i l y average and these subtractions accumulated f o r the phenological period as i n the standard degree day method. This procedure may be simply expressed as a summation of one quarter of the d a i l y 95. maximum minus the d a i l y minimum temperatures. The accumulated t o t a l s tabulated i n t h i s way are l i s t e d i n Table 8. The greatest deviation from the average was f i f t y - s i x 'Y1 units i n the year 1950. The average number of 'Y1 units per day during the growth period i n the month of September f o r the f i v e years l i s t e d i s 5.3 and f o r the l a s t f i v e days of the same phenological period i t i s 5.0 'Y1 units per day. I f the precision of the prediction must be wi t h i n f i v e days of the actual harvest date then only a t o t a l of twenty-five ,Y* units i s permissable. That i s , the deviation from the average cannot be greater than twenty-five fY f u n i t s . The data i n Table 8 are w i t h i n the required l i m i t s three out of f i v e years. The precision gained i n the u t i l i z a t i o n of the phenological data i n t h i s way cannot be considered as adequate, but i t i s an improvement over the other methods examined i n t h i s paper. I t also gives r i s e to the v a l i d i t y of the Heat Unit Theory, with i t s accompanying confusion of base temperatures i n the prediction of apple maturity when the phenological period i s of comparatively short duration. I t should be emphasized here that the use of average temperatures and the subsequent compilation of degree days, as w e l l as using a minimum temperature with the r e s u l t i n g 'X1 units and the night temperatures as 'Night 1 units are a l l based on the Heat Unit Theory and are an expression of various forms of that Theory. The use of the 96 range of temperature values with i t s expression i n 'Y1 units as outlined above i s d e f i n i t e l y a departure from the Heat Unit Theory, Yet another aspect of phenological investigations i s that of the part played by the sun. Sunshine or hours of sunshine as such appears to bear but l i t t l e r e l a t i o n s h i p to the length of the phenological period. Table 9 shows that i n 1951'there was a t o t a l of 937*0 hours of sunshine i n a growing period of 132 days, while i n 1949 there were 1075.6 hours of-sunshine with only 118 days i n the phenological period. The apparent rel a t i o n s h i p thus f a r indicated was shattered i n 1952 when the growing season contained a t o t a l of 1095.4 hours of sunshine but required 135 days to bring the apples to harvest maturity. Similar anomalies occurred i n other years. The month of May i n 1950 had fewer hours of sunshine than had May of any other year l i s t e d . But t h i s did not extend the growth period compared to years when more hours of sunshine were recorded i n May as might be expected i f sunny weather around blossom time affected the length of growing season of the apple. I t would appear that sunny periods around blossoming time do not have a consistent effect on the length of the phenological period. A s u b s t i t u t i o n of solar r a d i a t i o n for sunshine data would not seem to be j u s t i f i e d from the work done i n t h i s i n v e s t i g a t i o n . Solar r a d i a t i o n units are available f o r 97. only the three years 1950-1952 as int e r e s t i n t h i s approach to the growth problem i s of r e l a t i v e l y recent o r i g i n . The data i n Table 11 indicates that an accumulation of solar r a d i a t i o n units would not be useful i n predicting harvest maturities of the apple. Too much v a r i a b i l i t y i n the t o t a l number of Langleys e x i s t s from year to year. There does appear to be some rel a t i o n s h i p or at least a s i m i l a r trend, between the number of days i n the phenological period, the t o t a l degree days, t o t a l hours of sunshine and t o t a l solar r a d i a t i o n units f o r the years 1950-1952. Unfortunately, there are no solar r a d i a t i o n figures available f o r the growing periods i n 1948 and 194-9. One can only conjecture as to how the r a d i a t i o n f o r these years would f i t i n with the trend established i n the years 1950-1952. Certainly the other factors as the t o t a l degree days, hours of sunshine, and number of days i n the growth period for the years 1948 and 1949 tend to destroy any re l a t i o n s h i p between each other once the data from these years are examined. The apparent lack of significance attached to sunlight and solar r a d i a t i o n expressed above should not be construed as meaning these factors have no effect on plant growth. The effect of l i g h t and duration of l i g h t are widely known and recognized as being extremely important to the growth processes of plants (38, 42, 46, 53). For instance, very recent work by Liverman and Bonner (32) suggest that v i s i b l e red l i g h t activates a p a r t i c u l a r -9.8. protein i n plant tissue i n order that i t may combine with the es s e n t i a l plant hormone, auxin, to produce growth. The auxin and protein are combined with the help of l i g h t during the day and the union i s broken down during the night. Thus the role of l i g h t and darkness i n plant growth cannot be emphasized too much. However, the data on sunlight and solar r a d i a t i o n are compiled In t h i s i n v e s t i g a t i o n i n a manner purported to show that an accumulation of these units alone are of doubtful value i n prediction work. I t may be that a co r r e l a t i o n of many factors as l i g h t , moisture, temperature, wind v e l o c i t y , etc., i n a manner s i m i l a r to that suggested by Clements (18) and Smith (53) i s a more e f f i c i e n t method of attacking the problem of plant growth than the study of only one such factor alone. The b r i e f discussion of the d i f f e r e n t temperature s t a t i s t i c s , sunshine and solar r a d i a t i o n units as outlined above i s f a r from complete but serves to i l l u s t r a t e t h e i r importance as i n d i v i d u a l factors i n maturity prediction studies. However, our main interest i n t h i s paper i s the s t a t i s t i c of average temperature and i t s r e l a t i o n to growth i n the plant. So f a r the examination has been directed to four and f i v e years 1 data. I t becomes necessary to see whether data collected over a longer period of time w i l l introduce any new aspects of the problem. Degree days calculated f or the years 1940-1952 at 99 Ottawa as i n Table 13 reveal the same fluctuations that were observed i n the data from only f i v e years. In other words there i s considerable v a r i a b i l i t y i n the t o t a l degree days for a l l base temperatures and a l l years. Contrary to what may have beenjexpected there i s no increase i n pre c i s i o n gained by taking the deviation from a th i r t e e n year average rather than a deviation from a f i v e year average. A c t u a l l y the reverse i s true, f o r upon examining the deviations from the t h i r t e e n year average for the base of 50 °F, as i n Table 14 and comparing i t with the information given i n Table 5 i t may be observed that the range of deviation i n Table 5 varies from plus 145 to minus 159 degree days; while i n Table 14 the range varies from plus 384 to minus 217» That i s , the in c l u s i o n of more years into the survey merely introduced abnormal years as 1940 and 1944 which were very much out of l i n e with other years. However, i t does stress the necessity for the inc l u s i o n of as many years 1 data as possible i n order that a more complete picture of the problem may be obtained. Obviously no one base temperature (at l e a s t of those base temperatures used i n t h i s investigation) appears to give a consistent increase i n precision over the other. But the base temperature of 42°F, occupies a medial p o s i t i o n . Years such as 194l and 1948 appear to be "average" years and a l l base temperatures work reasonably w e l l i n those years. That i s , precision i s 100. gained i n i n d i v i d u a l years rather than f o r i n d i v i d u a l base temperatures. I t i s i n t e r e s t i n g to note that the s e l e c t i o n of the actual base temperatures for summer months i s r e l a t i v e l y unimportant as long as i t i s 50°F. or lower. Table 15 shows that f o r the summer months of June, July and August there i s no change i n the range of extreme years f o r a l l base temperatures. But the selection of base temperatures f o r the months of May and September may be much more important as i t i s i n these months when the temperature fluctuates r a p i d l y . Therefore, i t becomes imperative that the s e l c t i o n of base temperatures f o r those months be c a r e f u l l y chosen with due regard to minimum or optimum growth temperatures fo r a s p e c i f i c l o c a t i o n . Some ad d i t i o n a l rather i n t e r e s t i n g information may be gathered from Table 16. Here the t o t a l degree averages are l i s t e d f o r f i v e years' data and f o r t h i r t e e n years 1 data at Ottawa, using four d i f f e r e n t base temperatures. There i s a remarkably close agreement between the two averages f o r each base temperature leading to the conclusion that i f one i s interested only i n an average for data on phenology, a f i v e year time i n t e r v a l may s u f f i c e . However, as e a r l i e r observed i n t h i s paper, i f i t i s desirable to ascertain the range of yearly v a r i a b i l i t y then i t may be necessary to include ten or more years* c l i m a t o l o g i c a l and growth data 101. i n the i n v e s t i g a t i o n . The i n c l u s i o n of data from Summerland, B, C,, serves to i l l u s t r a t e the effects of geographical p o s i t i o n on phenological investigations. For instance, Ottawa i s situated at a l a t i t u d e of 45°24*; Summerland i s located at a l a t i t u d e of 49 034 !. A comparison bet\*een Table 17 and Table I shows that i n general, Summerland has warmer average temperatures than are experienced at Ottawa, The grand average for the growing season at Summerland i s 63.8°F, while at Ottawa i t i s 62,7°F. The warmer temperatures at Summerland resulted i n a longer phenological period with a subsequent larger t o t a l number of degree days than was experienced at Ottawa, Comparable figures are not available f o r Summerland and Ottawa f o r the t h i r t e e n year period of 1940-1952 since records at Summerland were not complete for the war years of 1942-1945* However, the data f o r nine years as l i s t e d i n Table 18 shows s i m i l a r yearly variations to that of data recorded at Ottawa, The deviations from the average i n Table 19 show that at Summerland there i s the same tendency f o r "average" years as at Ottawa, But the years are not necessarily the same and indeed are not i n these data. At Ottawa the "average" years were i n 1941 and 1948; while at Summerland the "average" years were 1946 and 1951. A s i m i l a r conclusion with regard to base 102. temperatures was observed at Summerland as at Ottawa. That i s , no one base temperature appeared to be very much better than the others with the possible exception of the Series L combination of temperatures. This s e r i e s , which consists of the employment of a base temperature of 50°F. f o r May, 42°F. i n June, 3h°F. i n July and August and 46°F. i n September, appeared to be best suited to the conditions at Summerland. A base temperature of 42°F. occupied a medial pos i t i o n and the base temperature of 34°F. was le a s t s a t i s f a c t o r y at Summerland. The same sort of information i s obtained at Summerland with regard to the range i n t o t a l degree days between extreme years (Table 20) as was observed at Ottawa. That i s , the months of June, July and August are not c r i t i c a l months i n the selection of base temperatures but car e f u l consideration should be given to base temperatures selected f o r the months of May and September. From Table 21 i t would appear that with very few exceptions more degree days were required to mature f r u i t at Summerland than at Ottawa, despite the fact that temperatures were generally warmer at Summerland than at Ottawa. However, t h i s i s i n accordance with the observations made by others (19, 25, 31» 6 0 ) , that i s , under ce r t a i n conditions of higher temperature, maturation of f r u i t s and vegetables may be a c t u a l l y retarded. I t may be that the range of f l u c t u a t i o n 103. between night and day temperatures at Summerland i s greater than at Ottawa and t h i s greater f l u c t u a t i o n has an adverse effect on growth and ripening. In addition, geographical p o s i t i o n and i t s effect i n length of day has not been explored f u l l y i n t h i s i n v e s t i g a t i o n . But whatever the reason, there i s a d e f i n i t e increase i n the t o t a l degree days accumulated at Summerland over those accumulated at Ottawa and t h i s i s r e f l e c t e d i n the length of the growth period as i s shown i n Table 22. The average number of days to mature f r u i t at Ottawa over a period of thirteen years was 131 while at Summerland the average for a nine year period was 146 days. I t therefore takes f r u i t an average of f i f t e e n days longer to mature at Summerland than at Ottawa. Under the cl i m a t o l o g i c a l conditions e x i s t i n g at Ottawa there i s considerably more yearly f l u c t u a t i o n i n the length of the phenological period than at Summerland. Phenological periods i n i n d i v i d u a l years at Ottawa may deviate as much.as 14 days but at Summerland the greatest deviation of the years l i s t e d i n t h i s investigation i s only 8 days. The data from Summerland are not quite comparable to those of Ottawa because of the missing years, 1942-1945. However, i t would appear that using the t o a l number of days as a c r i t e r i o n for prediction purposes would be more sa t i s f a c t o r y at Summerland than at Ottawa. Further, and with respect to the data 104 gathered i n the present investigation i t i s doubtful whether, as has been suggested by Haller (25) the number of days i n the phenological period could serve as a method f o r predicting the harvest dates of apples. The work thus f a r examined has indicated that average d a i l y temperature may not be the correct factor to use i n the prediction of harvest dates of apples. Actual measurements of growth related to average temperature were not available f or the years observed. Information of t h i s kind was supplied using the Ottawa seedling 277 and the Mcintosh variety on East Mailing I , From the measurements taken on seven i n d i v i d u a l apples on the 0-277 seedling and l i s t e d with average temperatures as i n Table 24 i t i s not possible to observe the c y c l i c growth that has been noted i n the l i t e r a t u r e (30, 31> 59)• Nor does there appear to be much c o r r e l a t i o n between average temperature and average growth. For instance during the period June 3 to June 5 the average growth per day was 0,0893 cm, with an average temperature of 53«4°F, During the period June 5 - 8 the average growth was 0,0805 cm, with an average temperature of 64,1°F, The growth i s about the same although the average temperatures are quite d i f f e r e n t . The argument of c y c l i c growth with d i f f e r e n t optimum temperatures would not account f o r t h i s phenomenon as the temperature differences were recorded i n what could 105. only be one phase of the c y c l i c growth. A similar sort of thing occurred from July 6 to July 10. However, there does appear to be a f a i r l y rapid increase i n the rate of growth up to June 19 and then a s l i g h t l y lower rate of growth u n t i l July 1 whence the growth hovered about the .05 cm. mark u n t i l the end of the season. The f i r s t two periods would agree with those observations i n the l i t e r a t u r e , but instead of the l a s t phase increasing i n rate of growth t h i s i n v e s t i g a t i o n found the rate to decrease. C y c l i c growth may be present i n the data as found i n t h i s investigation but i t appears d i f f i c u l t to associate these periods with any optimum average temperature. I t i s i n t e r e s t i n g to note that the c o r r e l a t i o n c o e f f i c i e n t calculated f o r the data i n Table 24 i s negative. That would lead to the conclusion that growth decreases with increasing temperature. Unfortunately, with an early v a r i e t y of apple, cessation of growth or f r u i t maturation coincides with the a r r i v a l of warmer summer temperatures. I t i s therefore d i f f i c u l t to disassociate the ef f e c t s of temperature from the natural processes of maturation. The c o e f f i c i e n t of c o r r e l a t i o n calculated.here i s -0.405 which proves to be i n s i g n i f i c a n t according to the t test as In Goulden (23). However, i t i s very nearly s i g n i f i c a n t and I t may be that i f more data had been avail a b l e the r e s u l t s would have been s i g n i f i c a n t . 106. Since the data on the early seedling v a r i e t y 0-277 may be influenced by factors other than c l i m a t o l o g i c a l , one might expect the data on growth and temperature as collected from the Mcintosh v a r i e t y to be much more s a t i s f a c t o r y . That i s , observations are made over a longer period of time embracing a greater range of temperatures. However, on examination the Mcintosh data as recorded i n Tables 25 and 26 are even more d i f f i c u l t to interpret than those observed with the 0-277 seedling. The average rate of growth i n the Mcintosh variety was maintained i n excess of .06 cm. up to August 12, from whence the rate of growth declined but never a c t u a l l y stopped. Rather steady growth took place from June 26 to July 15, but the average temperature varied from 59°F. to 73°F. Evidence of c y c l i c growth i s not r e a d i l y observable i n the Mcintosh apple. But one might say that there i s a period of rapid growth from bloom to July 15» then a period of i r r e g u l a r growth follows ending about August 15 and f i n a l l y there i s a period during which very l i t t l e growth takes place and which does not end u n t i l the apple Is removed from the tree. There i s no reason to suspect a f l u s h of growth toward the end of the season. But i n t h i s respect i t would be well to remember that during the summer and autumn of the year 1953? moisture was d e f i n i t e l y a l i m i t i n g factor i n the experimental orchard. A good r a i n 107. which f e l l from August 10 to August 12 i s no doubt responsible for the increase i n rate of growth shown f o r that period of time. The c o r r e l a t i o n c o e f f i c i e n t for the data recorded on the Mcintosh v a r i e t y was 0.032 i n d i c a t i n g no r e l a t i o n between average growth and average temperature. One should have a c o r r e l a t i o n c o e f f i c i e n t of at l e a s t 0.8 before one could state p o s i t i v e l y that for a given average temperature a s p e c i f i c rate of growth w i l l be obtained. From the data i n t h i s i n v e s t i g a t i o n i t would appear that the growth or maturation of the apple f r u i t i s not related to average temperature but i t must not be assumed that these r e s u l t s are conclusive. Further work should be done, p a r t i c u l a r l y i n regard to the actual measurement of apple growth. Summary The a p p l i c a t i o n of the Heat Unit Theory i n the forecasting of harvest dates of vegetables i n commercial plantings throughout Canada prompted an inves t i g a t i o n to study the possible use of the Theory i n the prediction of harvest maturity i n apples at the Central Experimental Farm at Ottawa. The primary purpose of the inves t i g a t i o n was the accurate prediction of harvest maturity of the apples I 108 through the medium of an accumulation of heat u n i t s , commonly known as degree days, for each of the years studied. Only the c l i m a t o l o g i c a l factors of temperature, sunshine and solar r a d i a t i o n were considered i n the study and of these temperature was the factor most c r i t i c a l l y analyzed. In the preliminary inquiry four years phenological data f o r the period 193+8-1951 were arranged i n a manner calculated to show the v a r i a b i l i t y i n t o t a l degree days ex i s t i n g between years and between apple v a r i e t i e s . Several of the more important v a r i e t i e s grown at the Central Experimental Farm such as Melba, Hume, Mcintosh and Niobe were selected as study mediums. The beginning of the phenological period of each variety was taken as being that of the date of f i r s t bloom of the v a r i e t y . Maturity indices were taken from data gathered by the Record Section and from those of the Low Temperature Storage Research Section. I t was found that harvest dates as recorded i n the f i e l d were as good as, i f not better than, optimum harvest dates selected through storage research. Ho r e l a t i o n could be observed between the accumulated hours of sunshine and t o t a l degree days or the length of the phenological period. In the next phase of the work, phenological data from the year 1952 were added to the four years examined previously. Only one v a r i e t y , that, of Mcintosh on the root 109. East Mailing I was used as the study medium i n t h i s phase and throughout the r e s t of the in v e s t i g a t i o n . Refinements i n the phenological period were made by st a r t i n g the period at f u l l bloom and at ten days before f u l l bloom of the Mcintosh v a r i e t y . Beginning the period ten days before f u l l bloom achieved maximum prec i s i o n i n the t o t a l degree days f o r the f i v e years examined. Base temperatures of 34°F., 42°F., 46°F., 50°F., constantly maintained throughout the period were tested, as well as ce r t a i n combinations of these base temperatures. No one base temperature or combination of temperatures appeared more e f f i c i e n t than any other, although the base temperature of 42°F. maintained throughout the period occupied a medial p o s i t i o n . The possible substitution of temperature s t a t i s t i c s other than the average i n the c a l c u l a t i o n of heat units was explored. I t was found that the su b s t i t u t i o n of either the minimum temperature or the night temperature for average temperature did not materially a i d i n the p r e c i s i o n of a pred i c t i o n based on heat u n i t s . However, an accumulation of a range of temperatures, which bears no r e l a t i o n to the Heat Unit Theory, being a departure from the assumption of base temperatures, gave the most consistent r e s u l t s of a l l methods attempted. The i n c l u s i o n of the cli m a t o l o g i c a l data on n o . sunshine and solar r a d i a t i o n from the year 1952 into the inv e s t i g a t i o n did not appear to improve the r e l a t i o n s h i p between the accumulated hours of sunshine or the accumulated solar r a d i a t i o n units and the t o t a l degree days or the length of the phenological period. The time i n t e r v a l at Ottawa i n the l a s t phase of the i n v e s t i g a t i o n was lengthened to include data from the th i r t e e n years 1940-1952. In addition, nine years-data from the Summerland Experiment Station were included i n order that the e f f e c t of geographical p o s i t i o n could be noted. Irrespective of base temperature, the deviation i n t o t a l degree days f o r each year from the average was not consistently low enough for predi c t i o n purposes at either S t a t i o n . Precision was acquired within i n d i v i d u a l years rather than f o r i n d i v i d u a l base temperatures. That i s , "average" years were noted during which a l l base temperatures resulted i n good p r e c i s i o n . These "average" years were not necessarily common to both Stations. The c r i t i c a l months for the establishment of a base temperature were found to.be May and September. The s e l e c t i o n of base temperatures f o r the months of June, July and August was r e l a t i v e l y unimportant to the pr e d i c t i o n as long as the base temperature selected was below 50°F. The average d a i l y temperature at Summerland was somewhat warmer than that at Ottawa; yet more degree days 111. were required to mature the apple f r u i t at Summerland than at Ottawa. At Ottawa there was l i t t l e difference In the average t o t a l degree days computed from f i v e years 1 data and the average calculated from thirteen years* data. In a study designed to note the effect of average temperature on the rate of increase i n size of the apple f r u i t i t was found that f o r the early Ottawa seedling 277 and for the Mcintosh va r i e t y very l i t t l e c o r r e l a t i o n could be established between growth of the f r u i t and average temperature. The t o t a l number of days contained w i t h i n the phenological period was found to give more precise predictions than the employment of the Heat Unit Theory based on an accumulation of degree days. Conclusion A study of the p r a c t i c a l a p p l i c a t i o n of phenology i n predicting harvest dates of the apple through the medium of the Heat Unit Theory indicates that: Starting the phenological period ten days before f u l l bloom results i n greater precision than when i t i s begun at f u l l bloom or even at f i r s t bloom. No one base temperature or combination of base temperatures appears to be better than any other. C r i t i c a l 112. months f o r the establishment of base temperatures are May and September as long as these temperatures are 50°F. or lower. Precision of harvest predictions i s acquired within i n d i v i d u a l years rather than f o r p a r t i c u l a r base temperatures. That i s , "average" years occur during which a l l base temperatures r e s u l t i n good pr e c i s i o n . This i s true f o r both Ottawa, Ontario, and Summerland, B. C , although the years are not necessarily the same f o r these Stations. Ordinary picking or harvest dates when used as a point at which to end the phenological period are as good as optimum dates procured through maturity indices studies i n cold storage. The average d a i l y temperature at Summerland i s somewhat warmer than at Ottawa, yet more degree days are required to mature the apple f r u i t at Summerland than at Ottawa. Very l i t t l e r e l a t i o n can be observed between the accumulated hours of sunshine and the t o t a l number of degree days or the length of the phenological period. In t h i s i n v e s t i g a t i o n no r e l a t i o n s h i p can be shown between average temperature and average growth i n either the Ottawa seedling 277 or the Mcintosh v a r i e t y on East Mailing I root. 113 An accumulation of a range of temperatures gives more consistent r e s u l t s i n harvest predictions than does an accumulation of heat units based on minimum, average or night temperature s t a t i s t i c s . The t o t a l number of days contained within the phenological period gives a more precise prediction than an accumulation of degree days, p a r t i c u l a r l y at Summerland, B. C. 114. L i t e r a t u r e Cited 1. Abbe, Cleveland. F i r s t report on the r e l a t i o n between climates and crops. U.S.D.A. Weather Bureau, Washington. 1905. 2. Appleman, CO. and S.V. Eaton. Evaluation of cl i m a t i c temperature e f f i c i e n c y f o r ripening processes i n sweet corn. Jour. Agr. Res. 20:795-805. 1921. 3. Baker, G.A. and R.M. Brooks. Climate i n r e l a t i o n to deciduous f r u i t production i n C a l i f o r n i a . I I I . E f f e c t of temperature on number of days from f u l l bloom to harvest of apricot and prune f r u i t s ; Proc. Amer. Soc. Hort. S c i . 45:95-103. 1944. 4. Bandurski, R.S., F.M. Scott, and F.W. Went. E f f e c t of temperature on the color and anatomy of the leaves. Paper read at the Meeting of Am. Assoc. Adv. S c i . P a c i f i c Coast D i v i s i o n . 1951. 5. Barnard, J.D. Heat units as a measure of canning crop maturity. The Canner, A p r i l , 1948. 6. Blackman, G.E. An analysis of the effects of seasonal l i g h t i n t e n s i t y and temperature on the growth of plants i n the vegetative phase. Int. Hort. Congress. 1952. 7. Blake, M.A. Factors which influence the blooming and ripening period of peaches. Proc. Am. Soc. Hort. S c i . 8:95-101. 1911. 8. Blake, M.A. Growth of the f r u i t of Elberta peach from blossom bud to maturity. Proc. Am. Soc. Hort. S c i . 22:29-38. 1925. 9. Blake, M.A. and O.W. Davidson. The Hew Jersey standard for judging the growth status of the Delicious apple. New Jersey Agr. Exp. Sta. B u l l . No. 559. 1934. 10. Bomalaski, H.H. Growing degree days. Food Packer. July and August. 1948. 11. Brooks, R.M. E f f e c t of d a i l y temperature on the date of picking apricots and pears. The Blue Anchor. 22:17-20. 1945. 115 12. Brooks, Held M. Climate i n r e l a t i o n to deciduous f r u i t production i n C a l i f o r n i a , I I • E f f e c t of the warm winter of 1940-41 on ap r i c o t , plum and prune v a r i e t i e s i n northern C a l i f o r n i a , Proc. Am, Soc, Hort. S c i . 40:209-211. 1942. 13* Brooks, Reid M. Apricot harvest predictable. C a l i f . Agr. 5:1-3. 1951. 14. Brooks, Reid M. and Guy L. P h i l p . Climate i n r e l a t i o n to deciduous f r u i t production i n C a l i f o r n i a , I. E f f e c t of the warm winter of 1940-41 on peach and nectarine v a r i e t i e s i n northern C a l i f o r n i a . Proc. Am. Soc. Hort. S c i . 39:190-194. 1941. 15. Brown, D i l l o n S. Climate i n r e l a t i o n to deciduous f r u i t production i n C a l i f o r n i a . V. The use of temperature records to predict the time of harvest of a p r i c o t s . Proc. Am. Soc. Hort. S c i . 60:197-203. 1952. 16. Camus, G.C. and F.W. Went. The thermoperiodicity of three v a r i e t i e s of 21 Bot. 39:521-528. 19 Nicotiana tabacum. Am. Jour. - £ 2. . . 17. Chandler, W.H., M.H. Kimball, C.L. P h i l i p , W.P. Tufts, and G.P. Weldon. C h i l l i n g requirements f o r opening buds on deciduous orchard trees and some other plants i n C a l i f o r n i a . C a l i f . Agr. Exp. Sta. Bui. 611. 1947. 18. Clements, Harry F., Gordon Shigeura and Ernest K. Akamine. Factors a f f e c t i n g the growth of sugar cane. Univ. Hawaii A g r i . Exp. Sta. Tech. B u i . 18. 1952. 19. Eggert, F r a n k l i n P., A study of rest i n several v a r i e t i e s of apple and i n other f r u i t species grown i n Hew York State. Proc. Am. Soc. Hort. S c i . 57:169-178. 1951. 20. Ellenwood, C. W. Bloom period and y i e l d of apples. Ohio A g r i . Exp. Sta. Bui. 6 l 8 . 1941.' 21. Gardner, V.R., F.C. Bradford and H.D. Hooker, J r . The fundamentals of f r u i t production. McGraw-Hill Book Go., New York and London. 1939. 116. 22. Gardner, V.R., J.A. M e r r i l l and W. Toenjes. F r u i t setting i n the Delicious apple as influenced by c e r t a i n post blossoming environmental f a c t o r s . Mich. A g r i . Exp. Sta. Spec. Bui. 358. 1949. 23. Goulden, C.H. Methods of s t a t i s t i c a l a n a l y s i s . John Wilby and Sons, New York. 1939. 24. H a l l e r , Mark H. Days from bloom as an index of maturity f o r apples. Proc. Am. Soc. Hort. S c i . 40:141-145. 1942. 25. H a l l e r , M.H. Evaluation of indexes of maturity for apples. U.S.D.A. Tech. Bui. 1003. 1950. 26. Katz, Y.H. The r e l a t i o n s h i p between heat unit accumulation and the planting and harvesting of canning peas. Agron. Jour. 44:74-78. 1952. 27. Lamb, Robert C. E f f e c t of temperatures above and below freezing i n the breaking of rest i n the Latham raspberry. Proc. Am. Soc. Hort. S c i . 51:313-315* 1948. 28. Lana, E.P. and E.S. Haber. Seasonal v a r i a b i l i t y as indicated by cumulative degree hours with sweet corn. Proc. Am. Soc. Hort. S c i . 59:389-392. 1952. 29. L i l l e l a n d . 0. Growth study of the plum f r u i t . I . The growth and changes i n chemical composition of the Climax plum. Proc. Am. Soc. Hort. S c i . 30:203-208. 1933. 30. L i l l e l a n d , Omund. Growth study of the apricot f r u i t . I I . The e f f e c t of temperature. Proc. Am. Soc. Hort. S c i . 33:269-279. 1936. 31. L i l l e l a n d , 0 . , and L. Newsome. A growth study of the cherry f r u i t . Proc. Am. Soc. Hort. S c i . 32:291-299. 1935. 32. Liverman, James and James Bonner. The mechanism of growth. Paper given at Am. Inst, of B i o . S c i . Wise. 1953. 33. Livingston, B.E. Physiological temperature indices f o r the study of plant growth i n r e l a t i o n to c l i m a t i c conditions. Phys. Res. 1:339-420. 1916. 117 34. Lu, C.S. and R.H. Roberts. E f f e c t of temperature upon the setting of Delicious apples. Proc. Am. Soc. Hort. S c i . 59:177-183. 1952. 35. Magoon, C.A. and C.W. Culpepper. Response of sweet corn to varying temperatures from time of planting to canning maturity. U.S.D.A. Tech. B u i . 312. 1932. 36. Magoon, C.A. and T.W. Dix. Observations on the response of grape vines to winter temperatures as related to t h e i r dormancy requirements. Proc. Am. Soc. Hort. S c i . 42:407-412. 1943. 37. Nightingale, G.T. E f f e c t of temperature on growth, anatomy and metabolism of apple and peach roots. Bot. Gaz. 92:581-639. 1935. 38. Nightingale, G.T. Light i n r e l a t i o n to the growth and chemical composition of some h o r t i c u l t u r a l plants. Proc. Am. Soc. Hort. S c i . 19:18-29 1922. 39. Nightingale, G.T. and M.A. Blake,. E f f e c t s of temperature on growth and composition of Stayman and Baldwin apple trees. New Jersey A g r i . Exp. Sta. Bui. 566. 1934. 40. Nightingale, G.T. and M.A. Blake. E f f e c t s of temperature on the growth and metabolism of E l b e r t a peach trees with notes on the growth responses of other v a r i e t i e s . New Jersey A g r i . Exp. Sta. B u i . 567. 1934. 41. Nightingale, G.T. and J.W. M i t c h e l l . E f f e c t s of humidity on metabolism i n tomato and apple. Plant Phys. 9:217-236. 1934. 42. Nuttonson, M.Y. Some preliminary observations of phenological data as a t o o l i n the study of photoperiodic and thermal requirements of various plant materials. Vernalization and Photoperiodism. Chronica Botanica Co. Waltham. 1948. 43. Overly, F.L. and W.J. Rogers. Relation of low spring temperatures to f r u i t growing i n Wenatchee d i s t r i c t of Washington. Wash. A g r i . Exp. Sta. C i r . 176. 1951. 118. 4 4 . Partridge, Newton L. A method for the estimation of the advancement of vegetation by the use of daily maximum temperatures. Proc. Am. Soc. Hort. Sci. 48:7-14. 1947. 4 5 . P h i l l i p s , E.E. The heat unit summation theory as applied to canning crops. Veg. Growers Assoc. Am. Annual Report. 1950. 46. Reath, A.N. and S.H. Wiltwer. The effect of temperature and photoperiod on the development of pea varieties. Proc. Am. Soc. Hort. S c i . 60:301-310. 1952. 4 7 . Roberts, R.H. Blossom structure and setting of Delicious and other apple varieties. Proc. Am. Soc. Hort. S c i . 46:87-90. 1945. 48. Roberts, R.H. The role of night temperature In plant performance. S c i . 98:265. 1943. 4 9 . Robertson, George W. Some agri-meteorological problems in Canada. Royal Meteorological Society. 4:1-11. 1953. 50. Ryall, A. Lloyd, Edwin Smith, and W.T. Pentzer. The elapsed period from f u l l bloom as an index of harvest maturity of pears. Proc. Am. Soc. Hort. Sc i . 38:273-281. 1941. 51. Sayre, C.B. Further studies of heat units for forecasting maturity of peas. New York State Agri. Exp. Sta. Annual Report. 1949. 52. Schilletter, Julian Claude and Harry Wyatt Rickey. Textbook of general horticulture. McGraw-Hill Book Co. Inc. New York & London. 1940. 53. Smith, Folmer. The plant producing power of sunlight as a function of geographical position and season. Inter. Hort. Congress. 1952. 54. Stanescu, P.P. Daily variations i n products of photosynthesis water content, and acidity of leaves toward the end of the vegetative period. Am. Jour. Bot. 23:374-379. 1936. 55. S t i l e s , Walter. Introduction to principles of plant physiology. Mathewen and Co. London. 1950.' 119. 56. Thomas, Walter. F o l i a r diagnosis: p r i n c i p l e s and practice. Plant Phys. 12:571-600. 1937. 57. Thornthwaite, C.W. Climate i n r e l a t i o n to planting and i r r i g a t i o n of vegetable crops. Paper prepared f o r XVII International Congress. Section of Climatology - Washington. 1952. 58. Tufts, Warren, P. Season temperatures and f r u i t ripening. A preliminary report. Proc. Am. Soc. Hort. S c i . 26:163-166. 1929. 59. Tukey, H.B. Time i n t e r v a l between f u l l bloom and f r u i t maturity f o r several v a r i e t i e s of apples, pears, peaches and cherries. Proc. Am. Soc. Hort. S c i . 40:133-140. 1942. 60. Tukey, Loren D. E f f e c t of night temperature on growth of the f r u i t of the sour cherry. Bot. Gaz. 114:155-165. 1952. 6l• Weinberger, J.H. Influence of temperature following bloom on f r u i t development period of Elberta peach. Proc. Am. Soc. Hort. S c i . 51:175-178. 1948. 62. Went, F.W. Response of plants to climate. S c i . 112:489-494* 1950. 63. Went, F.W. Thermoperiodicity. Vernalization and Photoperiodism. Chronica Botanical Co. Waltham. 1948. 64. Went, F.W. Simulation of photoperiodicity by thermoperiodicity. S c i . 101:97-98. 1945. 65. Went, F.W. E f f e c t of temporary shading on vegetables. Proc. Am. Soc. Hort. S c i . 48:374-380. 1946. 66. Went, F.W. and L. Cosper. Plant growth under controlled conditions. VI. Comparison between f i e l d and a i r conditioned greenhouse culture of tomatoes. Am. Jour. Bot. 32:643-654. 1945. 67. Wilson, Charles E., W.R. Boggs and Paul J . Kramer. Diurnal fluctuations i n the moisture content of some herbaceous plants. Am. Jour. Bot. 40:97-99. 1953.' 120 68. Winkler, A.J. Maturity tests f o r table grapes. The r e l a t i o n of heat summation to time of maturing and p a l a t a b i l i t y . Proc. Am. Soc. Hort. S c i . 51:295-298. 1948. 69. Winkler, A.J. and W.O. Williams. The heat required to bring Tokay grapes-to maturity. Proc. Am. Soc. Hort. S c i . 37:650-652. 1939. 70. Young, J.O. Growing of sv/eet corn f o r canning. Paper given at Canned Foods Assoc. Ont. Fieldman's School, Guelph. 1953. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0106298/manifest

Comment

Related Items