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Chemical aspects of physiological disorders of apple trees in the Okanagan Smith, I. C. 1934

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CHEMICAL ASPECTS OF PHYSIOLOGICAL DISORDERS OF APPLE TREES IB" THB QKAHAGAIT. I. C •Smith. Thesis presented to the Department of Chemistry for the degree of Master of Applied Science University of British, Columbia APRIL 1954 INTRODUCTION The experimental results presented in this paper are a part of a comprehensive; investigation into certain physiological diseases which are of exceptional sev-erity throughout the Okanagan f r u i t growing d i s t r i c t s of British Columbia. This investigation at present, is dealing with three disorders in the apple, known as Drought-Spot, Corky-core and Die-back. This investigational work i s a co-operative one» organized under the Provincial Advisory Committee with a sub-committee known as an Advisory Committee on Physiologi-cal Diseases in charge. The Chairman of the Committee is the Superintendent of the Experimental Station at Summerland » and themembers, technical o f f i c i a l s from the Provincial and Dominion Agricultural Departments. Details of the experi-mental work are under the direction of the Officer-in-charge, Dominion Laboratory of Plant Pathology, Summerland. The characteristics of the three diseases as described by McLarty (48) are as follows, '"under the name Drought-spot, we include a f a i r l y large number of diseased conditions in the apple. In general, however, the disease; is characterized by the presence of spots of dead corky tissue at or near the surface and predominately around the calyx end. VZhen the disease i s severe, spots often coalesce and as the apple grows, large cracks are found on the surface. When the trouble is less severe, i t may appear only as a (2) browning of the epidermis around the calyx end resulting later in a russetted fruit'. ttA very distinguishing character of Drought-spot is that i t always occurs in the early stages of growth, appearing even before the apple is one inch in diameter. An apple when once affected does not, as some believe, recover. ••When this early attack is severe the apples are rendered en-ti r e l y unmarketable". "The term Corky-core refers to a condition in the f r u i t that makes i t s appearance considerably later than does Drought-spot. Usually i t is not perceptible u n t i l the apple i s half grown. It may continue to appear from that time on until the apple is picked. Unlike Drought-spot i t i s not externally apparent. It consists of one or any number of light brown corky areas either within the area of the core i t s e l f or in the inner flesh*. "By Die-back, we refer to the dying back in the tree of the previous years terminal growth. When tree growth starts, however, the twigs affected with Die-back either do not put out any leaves or i f they do the latter are weak and sickly and soon die. Later the bark on the tree begins to die and by midsummer the twig is entirely dead for some distance back. Below the point to which the"twig has died out new lateral shoots start out in several places, and one gets an impression of a rosette of growing twigs with the dead one standing out prominently in the centre"* (3) LITERATURE REVIEW Ion parasitic disturbances of plants may re-sult from a variety of causes, such as unsuitable environ-mental conditions of s o i l or a i r , or injurious mechanical in-fluences, or lack of inherent qualities. This investigation has to do with physiological disorders considered to be the result of unfavourable s o i l conditions, especially those which are of a physical or a chemical nature. De.f ioiencies Literature on the subject shows that deficiency diseases present symptoms similar in some degree at least, to those under consideration in this paper*. A condition of chlorosis has been attributed by numerous investigators to a deficiency of one or more of the essential elements. A number of papers have been written on chlor-osis caused by a deficiency of iron (22) (9) (2) ( l ) . The investigators believe that the disturbances are due to an in-sufficient supply of iron available to the tree as a result of an excess of lime in the s o i l , and state that the condition oan be eliminated by the application of suitable iron salts. Several other papers have been written on chlorosis as a result of a deficiency of manganese (65) (46) ( l l ) (19)* The authors describe a type of chlorosis peculiar to a manganese deficiency. McHargue (46) has found that such diseased tissue can be revived by the application of mangan-ese . He believes that manganese is just as indispensable as (4) Iron for..plant growth; An interesting paper hy Anderssen(3) describ-ing a physiological disorder of f r u i t trees in South Africa, provides information applicable to the disorders here. A typical chlorotio eonditon of the leaves and in some cases* dying back of the branches, was found to result from a defic-iency of copper in the plant tissues. A large number of s o i l and plant tissue analyses was made, and in recording the re-sults of his analyses i t is interesting to note that this in-vestigator found a definite increase in the amount of ash, especially calcium and iron, in the tops of diseased trees when compared to the tops of normal trees. Two other papers (ll)(72) describe the effects of deficiencies of zinc and boron on,plant growth. It i s evident that a certain amount of boron and zinc is essential in order to preserve a healthy condition in the plant. Chlorotio conditions in plants due to lack of magnesium have also been studied toy several investigators (64)(18)(30). The application of magnesium has been found to be correct the disorders in most of these cases. Many other investigations have been carried out on deficiencies of such elements as sulphur, (52)(53)(56) phosphorus, (25)(37)(39) and potassium 9(5l)(32)(4l)(66)(74) (?55(765(77)(?8)(79) in plants. In the latter case, the work of Wallace (74)(75)(76)(77)(78)(79) on the Leaf Scorch and Chlomsis of f r u i t trees, is perhaps outstanding in this f i e l d . (5) Wallace found from chemical analyses that these disorders» which in many ways are similar to the disorders in the Okan-agarn could he definitely attributed to a deficiency of pot* " assium available to the tree. He found that the application of potassium as a f e r t i l i z e r to trees suffering from the disorders would prevent the: appearance of pathological symptoms in most cases* but he found that in some cases, "the ordinary method of applying potassium manures i s not an effective means of obtaining a response in a reasonable period under the pre-vailing conditions'? and suggests that this lack of response is due to the ^inability of the potassium to penetrate the root system owing to the absorptive properties of the soils concerned*. In this particular investigation i t i s worthy of note that the author found the ash content of the dry material to be lower in the affected trees that in the normal trees* 'Excesses^ ' In contrast to disorders caused by mineral deficiencies^ we may also have disease exhibiting somewhat similar characters to those in the Okanagan, caused by mineral excesses. Overstimulated plants are frequently more suscept-ible to unfavourable climatic conditions and to parasitic in-vaders, but apart from this in most plants there i s a definite optimum concentration for practically a l l mineral elements. It has been shown that although plants are able to withstand moderate excesses of such elements as calcium and nitrogen, they are especially susceptible to abnormal amounts of the more toxic minerals such as copper, aluminium, manganese, (6) arsenic and boron ( l i ) (45)(67).-(14)* However» even such essential elements as the alkalies, calcium and nitrogen, when present in excesses may cause serious disorders (23)(33)(36) (38)(20)(I6)(2l). The following observation was made by G-lldehaus (20). "It should be borne in mind that the more nitrogen applied the greater w i l l be the drain on the mineral resources of the s o i l . Every pound of nitrogen used in plant nutrition requires also a certain amount of phosphorus * pot-assium and other mineral elements. Continued absorption of relatively large amounts of nitrogen w i l l cause an unbalanced nutrition when no provision i s made for the renewal of the soils supply of phosphorus and potassium, which are probably absorbed by the plant in amounts proportional to the nitrogen". This statement may reasonably have some bearing on the results of the experiment herein described since i t has been frequently observed that the application of nitrogen f e r t i l i z e r s to trees affected with Drough-spot, Corky-core or Die-back, aggravated their condition. If an unbalanced absorption of minerals is already taking place in trees affected with these diseases* the deleterious effect of nitrogen f e r t i l i z a t i o n on such trees might, be explained as resulting from this further unbalance in absorption as described by Gil&ehausv Prom the above papers, i t seems obvious that the requirements and tolerances of plants for the different mineral elements are restricted in most cases to a comparative-ly narrow range, and that the maintenance of health in plants ia- dependent upon a regulated supply of these minerals. :<7) • • ' Physical Conditionsof the S o i l in Relation to Water_ S u p p l y Many diseases have been described which are the r e s u l t of the physical s t r u c t u r e o f the s o i l in i t s relation t o the water supply. OEB of the most common physiological dis-orders which has been reported resulting from unfavourable water conditions is Bitter P i t . The characteristic symptoms of certain types o f the disease a s d e s c r i b e d by H e a l d ( 2 7 ) are very similar to those of the disorders under investigation in t h e Okanagan. The same m i s s h a p e n appearance of the f r u i t is present, and the general symptoms of the d i s e a s e d t r e e a r e s o similar that t h e p r o b a b i l i t y of these disorders r e s u l t i n g f r o m s i m i l a r causes may be s u s p e c t e d . H e a l d c o n c l u d e s t h a t t h e d i s e a s e o f Bitter Pit i s a *non parasitical malady a s s o c i -a t e d w i t h a d i s t u r b e d w a t e r r e l a t i o n " , and a l s o s t a t e s , t h a t " t h e r e h a s b e e n no u n a n i m i t y a s t o the e x a c t way i n which t h e d i s t u r b a n c e o p e r a t e s " . j?our theories are advanced to a c c o u n t for t h e p r e s e n c e o f d e a d c e l l s r e s u l t i n g f r o m a d i s t u r b e d w a t e r r e l a t i o n , b u t no d e f i n i t e e v i d e n c e i s advanoed favouring any one o f t h e s e theories. S e v e r a l c o n d i t i o n s r e l a t e d t o m o i s t u r e s u p p l y h a v e b e e n d e f i n i t e l y s t a t e d a s being a t l e a s t c o n t r i b u t o r y i n p r o d u c i n g the d i s e a s e a n d s t r e s s h a s b e e n l a i d b o t h on eEcessively dry conditions in the s o i l and also on c o n d i t i o n s o f s u p e r - m o i s t u r e . F l u c t u a t i n g v/ater c o n d i t i o n s a r e a l s o s t a t e d a s p l a y i n g an i m p o r t a n t p a r t . The work of ffic&lpin e ( 4 3 ) ( 4 4 ) on B i t t e r P i t , c o v e r i n g a p e r i o d o f f i v e y e a r s o f i n v e s t i g a t i o n on the d i s -o r d e r , h as presented e v i d e n c e i n favor o f a d i s t u r b e d water (8) relation as the cause of Bitter P i t . He states that "rapid alternations between dry and moist conditions combined with fluctuating temperatures during the growing stages of the f r u i t is the exciting cause of Bitter P i t " . Apparently the work of these two investigators provides evidence for a dis-turbed water relation as the cause of the disorder. Further evidence along this line has been pro-vided by the work of Came and his collaborators ( 1 5 ) . . These authors state that Bitter P i t is caused by Mthe with-drawal of water during the ripening process from the immature cells of the plant, due to a shortage of water in the f r u i t caused by picking in an immature condition". Contrary to Heaid these authors do not believe that the dlsea.se in initiated during the growing season. Cork is another disorder of similar nature to Bitter P i t which is: accounted to be the result of unfavourable water conditions. In a paper published by Mix (50) both the diseases, Cork and Drought-spot,, are described in detail. The symptoms of both are similar to Bitter P i t and their similar-ity to the Drought-spot, Corky-core and Die-back in the Okan-agan is very striking. They are probably identical. This author suggests that the origin of cork is the with-drawal of water from the fruits by the leaves during periods of high transpiration. In concluding, he makes the following interest-in t limitation, "Since, however, in a wet season and under con-ditions when there seems to be no deficiency of moisture, these disorders may occur in trees that have been previously diseased, (9) and since there is a tendency for certain trees, to become diseased year after year, insufficient s o i l moisture cannot be looked upon as the sole cause. Some not thoroughly under-stood factor or factors must operate to produce the disease under these conditions'** Cork spot of apples has also been described by Fisher (17). He attributes the disorder to the physical texture of the s o i l especially in relation to i t s moisture holding capacity. Further evidence is presented on drought as an important causal factor. An important physiological disease of citrus fruits has been investigated by Bartholomew (5)(6)(7)(8}» This disorder termed Endoxerosis is mainly characterized by a loss of water from the internal cells of the f r u i t with the production of gum in the conducting vessels and surrounding-tissues. These symptoms are very similar to the dying off of ceils- in the. apple* as reported by Mix and C ame etc. Bartholomew concludes that, like cork, the disease is due to, "the inability of the root system of the lemon tree when grown under arid or semi-arid conditions to supply f u l l y the water demands under conditions producing rapid evaporation"• Exanthema, a common physiological disease of citrus has been described by Came (12) as a result of unsatis-factory conditions especially in relation to s o i l moisture. The symptoms are similar to those of Die-back as exhibited by . . •. time.. f r u i t trees in the Okanagan. At the same/Thomas (73) in a publication on the same trouble, suggests that the disease i s ( 1 0 ) a result of a copper deficiency. Apparently both water conditions and mineral nutrition play a part in producing this disorder. An uncommon physiological disorder has been reported in a paper by Petherbridge, D i l 1 on-¥eston and JSewman (54)* The leaves of the trees were scorched in appearance and f e l l early and the f r u i t did not mature. But the most striking symptom was the death of the root systems of the affected trees below the three foot level* It is suggested that the drought conditions of the year concentrated the s o i l solution to such an extent that the permeability of the ab-sorbing parts of the roots was changed bringing about an ab-normally high intake of salts, especially iron, into the tree. In this connection It is interesting to note that chemical analyses of diseased and healthy tissue showed a much higher percentage of ash in the affected trees. The association of dead absorbing tissue with the disorders in the Okanagan is noticeable also and indieatiens are:that the disorder de-scribed in this paper by Petherbridge et a l , reaalts from a very similar cause to that producing the disorders here. The physiological disorders of f r u i t trees in the Okanagan have been investigated by McLarty (47). The. occurrence of the disorders was found to be associated with water conditions in the s o i l . Trees that had at some time suffered from an abundance of moisture were found to be subject to the disorders just as were those which had been exposed to a prolonged period of drought. One of the important observa™ (11) ' tions made by HcLarty was "a distinct difference apparent in the rootlet development in the two classes of trees*. In an unpublished report to the Committee-in-charge, McLarty (49) outlines his theory for the cause of these disorders. Direct quotation from this report affords the best means of introduc-ing this theory. " I . Observation shows that the occurrence of these diseases i s always associated with an excessive k i l l i n g of the absorbing root tissue of the affected trees. This k i l l i n g occurs at sometime previous to the time that the disease appears in the tree. In vigorous well fed trees this k i l l i n g off of the root-lets- may occur at least three years before the disease becomes evident. At. the time the disease does appear the rootlets may or may not have recovered to a normal conditions. £. This k i l l i n g off of the absorbing tissue of the roots does not, however, seriously interfere with the moisture intake from the s o i l . The evidence seems clear that trees can con-tinue to take up large quantities of water from the soil,, even when 90 per cent of the l i v i n g absorbing tissue has been k i l l -ed. This would indicate that the presence of living cells be-tween the s o i l solution and the xylem conducting vessels is not an essential factor in promoting and maintaining the transpiration current. 3. When only the absorbing tissue of the roots is killed and the usual intake of water continues, the tree is not as a rule stimulated to produce a new living absorbing system. Some new development takes place but the dead tissue may continue to (12) f u n c t i o n f o r a considerable p e r i o d of time, two to three years or more. Some trees have not shown more than ten to twenty per cent recovery i n three y e a r s . 4. I t i s i n the c r e a t i o n and continuance of t h i s dead absorb-in g t i s s u e that the r e a l cause of these d i s o r d e r s i s to be found. With no p r o t e c t i n g l a y e r of l i v i n g protoplasm i t i s reasonable to assume that the general laws of d i f f u s i o n w i l l govern the movements of a l l s a l t s d i s s o l v e d i n the s o i l s o l u -t i o n . Food m a t e r i a l s w i l l be present i n the t r a n s p i r a t i o n current i n the same proportions as they are i n the s o i l s o l u -t i o n . Such a c o n d i t i o n of a f f a i r s might of i t s e l f be quite responsible f o r a serious deraignment of the metabolic process-es. Of more importance and danger, however, i s the i n t r o d u t i o n to the t r a n s p i r a t i o n current of high percentages of the many t o x i c s a l t s present i n the s o i l s o l u t i o n . The attempt of the p l a n t to f u n c t i o n normally i n the presence of these adverse conditions i s a f a i l u r e . The r e s u l t s of t h i s f a i l u r e are to be found i n the appearance of the disea.se" . This theory p o s t u l a t i n g an unbalanced absorption of mineral elements as the r e s u l t of some type of root injury, i s the b a s i s of t h i s i n v e s t i g a t i o n . I t seems very reasonable that i f abnormal amounts of n u t r i e n t s are supplied to the tree f o r i t s metabolism, such excesses or d e f i c i e n c i e s might e a s i l y reaflt i n d i s o r d e r s of the type prevalent i n the Okanagan V a l l e y , e s p e c i a l l y when we consider the long l i s t of disorders caused by mineral d e f i c i e n c i e s and excesses as o u t l i n e d i n the l i t e r a t u r e . This subject of unbalanced absorption opens up (13) the question of the actual mechanism of mineral intake into the roots. The work of Scott and Priestly (68)(69) on the function of the root as an ahosrbtng organ has established many facts on the actual location of the absorbing surfaces. According to these writers the zone of extension behind the meris tern is the chief functioning zone is absorption. This zone usually contains the root hairs, but as pointed out by these authors, a l l absorption is not necessarily carried on by their agency. The anatomy of this absorbing region is f u l l y described by these authors. Owing to the loose construction of the cortex layer the authors suggest that the s o i l solution would diffuse in between the walls of the cortex layer as far as the endodermis. There i t would be stopped from further in-ward diffusion by the relatively impermeable network of the .Casparian Strip. In such a case, the actual functional absorb-ing surface of the root is the endodermal layer, and under such conditions, " i t is quite immaterial whether the actual surface of the root is increased by the production of root hairs or not**; • This same view is held by Priestly (57) who states that "The endodermis is apparently the c r i t i c a l layer for absorption and a l l solutes and water must pass directly through the protoplasm of the endodermal cells as a result of the obstruction caused by the Casparian Strips. Thus the passage of water through tie endodermis under normal conditions is controlled by osmotic phenomena and is always taking place in an inward direction". ( 1 4 ) This view that the selective action of plants in aborption takes place at the endodermal layer seems to he held by most authorities. The work of Priestly and his oollab-if orators ( 5 8 ) ( 5 9 ) ( 6 0 ( ( 6 1 ) ( 6 2 ) ( 6 3 ) on the actual mechanism of water and solute transference from the cells of the parenchyma to the xylem vessels h as done much to elucidate this question. The actual mechanism of solute intake by roots has been described by many authors. A recent paper by Petrie (55) provides evidence to show that the rate of ion intake by the root cells is dependent upon the rate of respiration of these c e l l s . The energy necessary for absorption being supplied by the respiration of the c e l l s . This view, that the energy derived from the v i t a l processes of the c e l l s , is necessary for the abosrption of ions is also held by Stewart ( 7 1 ) and by Blackman (10) and by Hoagland (29). Absorption of ions is apparently independent of the intake of water in normal roots. This has been shown by the papers of Hasselbring ( 2 6 ) Muenscher (51) and Scott ( 6 9 ) . , The selective action of the protoplasm of endodermal cel l s in the absorption of minerals has been widely proven. Maximov ( 4 2 ) states that "It would be erroneous to think that a plant like a simple wick passively absorbs a l l substances dissolved in the s o i l solution. Before entering the vessels of the plant the s o i l solution has to pass through a series of l i v i n g cells. These being endowed with selective permeability produce considerable changes inthe solution". Hoagland has also produced evidence to prove that the composition ' (15) of the sap within the xylern vessels is by no means the same as that of the s o i l solution (28). However, as mentioned by this same investigator (29) "The selective action of plants is a characteristic which is universally recognized and yet i t would appear that many erroneous ideas have been held concerning this question. "While i t is undeniably true that the plant may-absorb certain ions more readily than others i t is not true that a plant necessarily selects from a solution only or even chiefly those ions which are indispensable to its growth". This statement must be taken into consideration in the inter-pretation of the results of this experiment, yet undoubtedly -within certain limits the protoplasts of normal roots do discriminate in the absorption of minerals. Recently two papers have been published by Kramer (34)(35), describing the absorption of water through live and dead root systems. This investigator found that ab-sorption of v/ater takes places through dead root systems at a greater rate than through normal roots, and states that w i t appears that the living roots offer more resistance to the inflow of water than do dead roots. It is probable that this resultsfrom a decrease in the resistance to water movement from the periphery to the conducting vessels of the roots due to the destruction of the protoplasts and the differentiating permeable membranes". A destruction of the endodermal membranes would undoubtedly interfere with the normal absorption of solutes as well as that of water. The work by Straeburger (79) as (16) reviewed by Examer has shown that "when the differentially permeab le membranes were destroyed by k i l l i n g the roots, any kind of solute present in a solution surrounding the dead roots was readily absorbed**, and that "other substances which were then made available were absorbed in greater quantities than through living roots". Further support to this statement is afforded by Daubeny (15) as reviewed by Branch!ey. He states that where death of the absorbing tissue results from a corrosive toxin "The v i t a l i t y of the absorbing sufface of the roots is destroyed and is reduced to a condition of a simple membrane which by endosmosis absorbs whatever is present-ed to i t s external surfaces". Furthermore Maximov (42) has stated that "Substances incapable of penetrating through the protoplasm or unable to accumulate in the cells are aabsorbed by the roots (normal) from the s o i l in rather insignificant quantities. It i s necessary to open the conductive system and to let the solution directly into the cut vessels". Blow i f the root systems of affected trees were injured to such an extent that the s o i l solution could find i t s - way directly to the xylem vessels, i t is quite possible that this indiscrim-inate absorption suggested by McLarty and other authors does take place. The result of such a type of absorption would of course be an unbalance in the metabolism of the tree and physio-logical breakdown. Statement of Problem Taking the above observations into con-sideration the problem to be investigated in this paper, is to determine whether or not minerals are present in affected trees in different proportions than in normal trees, and in addition, i f possible, to produce similar variations, i f any, in the mineral content of small trees grown under controlled conditions. Approach to __the Problem The problem of investigating this loss of selective absorption as the primary cause of these disorders has been divided into two separate parts* The f i r s t consists of comparison of the ash analysis of different organs of a number of both healthy and diseased trees. It is reason-able to suspect that i f minerals are absorbed by the affected trees in discriminately, the proportions of one mineral to another in such trees w i l l vary from proportions between the same minerals in a healthy tree. Of course, as mentioned by Gile and Carew (2S) '*The r e l i a b i l i t y of ash analyses as a -sole means of diagnosing the cause of chlorosis in question-able . At the most the results of ash analyses should be taken as merely indicating the cause or confirming other evidence. The ash compostions of normal plants show, such wide variations and are effected by so many conditions that i t is sometimes unsafe to assume that of two lots of plants, those which have made the better growth, have an ash composition more nearly normal". Nevertheless i t is quite possible that i f an un-balance is present i t w i l l be reflected in the ash analysis of the tissue in question. The main di f f i c u l t y in this project lay in obtaining.suitable material for analysis. The degree of health of an apple tree is d i f f i c u l t to estimate. Consequently ( 1 8 ) Healthy trees were selected on the basis of their past freedom from the disease as well as their external appearances. Mo such d i f f i c u l t y was experienced in the selection of diseased trees» their condition was quite apparent. The ash content of plant tissue varies widely with the part of the tree from which the sample is taken, and such an unbalance might be more apparent in one organ than in another. In addition many other variables had to be eliminat-ed such as climatic and s o i l conditions, agej variety and cultural treatment, in order to obtain comparable samples for analysis. It was also f e l t desirable to analyze composite samples covering a number of trees in both the healthy and diseased stages rather than individuals. The second part of the work has been to graw small apple trees under controlled conditions and to injure a r t i f i c a l l y the root systems of some of these trees in an attempt to reproduce conditions found in the f i e l d . Absorption would then proceed through dead tissue except in the checks, and i f the same variation, i f any, could be found between the chemical composition of the trees with injured root systems and those with normal root systems, as is found between diseased and healthy trees in the f i e l d , i t would seem possible that rootlet injury with a resulting loss of selective absorption may be considered at least a contributory cause of these dis-orders. While i t was recognised that tree root conditions are very different in water culture to those in the f i e l d , at (19) the same time both the check trees and the treated trees were under the same conditions, and in addition, a much higher degre of control could be maintained. The small trees used were a l l of approximately the same size and had been grown vegetatively from a root stock known as Ifo. 327 • By this method the usual variation of inherent characteristics as expressed in seed-lings was avoided* Methods and Technique^ The f i r s t part of the investigation was contained in the analyses of different parts of healthy and diseased trees in the f i e l d . In this case the analytical work was divided into two portions, the f i r s t on fru i t buds and the second on two year old twig growth, For the f r u i t bud analysis trees were selected from three different orchards in the valley. The f i r s t group was taken from a diseased experimental orchard in Kelowna, and was made up of thirty trees suffering from advanced forms of the three disorders mentioned above. The second group consist-ed of ten trees taken from an orchard in Summerland in which Drought-spot, Corky-core, and Die-back had never been apparent, but in which over thirty per cent of the trees had suffered from another physiological disorder known as Collar Rot. The third group of seventeen trees was taken from a commercial orchard in Kelowna. These trees were to a l l external appear-ances in normal health, and continuous records covering their complete bearing age. showed freedom from a l l forms of physiol-1' Supplied by R.&.Palmer, Dominion Experimental Station, Summerland, B.C. (20) ogical disease. These trees were a l l Mcintosh in variety. The age; of the trees in Group No.1 and Ho.2 was fifteen years, and that of Group Ho. 3 was ten years. The climatic and s o i l con-ditions of the f i r s t and third group trees were identical. Group No. 2 taken as i t was from Summerland, was under slightly different climatic and s o i l conditions from the other two groups. The f r u i t hud samples were taken during the f i r s t week in April, 1932, just before the breaking period. Analysis was made on composite samples covering each group according to the methods outlined below. Results are shown in Fig.T Each determination given is the average of eight checks made on the same sample. For the twig analyses a group of five trees was chosen from each of the three orchards raentioned above. These trees were selected from those from which the bud samples were obtained. In addition, a fourth group was added taken from an orchard in Peaohland. Five years continuous records showed that this orchard was suffering from these physiological dis-eases thought to be the result of conditions of super-moisture. The age and variety of the Peachland trees was the same as Groups Ho. 1 and No. 2. Soil and climatic con-ditions were, however, considerably different from thoss of the other groups. The trees were sampled in April, 1933, just before the buds h ad broken. Only two year old twig growth was taken in a l l cases. The results of these analyses are shown in Fig.'i^ . '(21)' ' Methods of Analysis. The samples for analysis were made up of equal amounts of tissue from each tree in the group. Drying. The bud samples were dried in an electric oven for twelve to fourteen hours at I 0 0 ° C . The dry material was ground in a meat chopper for ashing. The twig samples were cut into thin sections by a revolving knife. These sections were dried in an electric oven at 1 0 4 ° C for the forty-eight hours and then ground in a meat chopper for ashing* Nitrogen. Was determined by the standard Kjeldahl-Gunning method to include nitrate nitrogen ( 4 0 ) . Sulphur. Was determined by the magnesium nitrate method ( 4 ) . The results are the average of at least three checks on the same sample• Ashing. Ashing of the dry material was done in a muffle fur-nace at a dull red heat for twenty-four hours. The ash obtain-ed was f a i r l y free from Charcoal. A known quantity of the ash was digested with acid six normal hydrochloric/on a water bath for two to three hours. The residue, sand and charcoal was filtered off and weighed. The weight of pure ash was corrected by subtraction of the weight of this fraction from the weight of crude ash. The f i l t r a t e containing the mineral elements in solution was evaporated to dryness and the residue was heated at 104°C for twelve hours to dehydrate the s i l i c i c acid. Digestion of the residue was carried on with dilute hydrochloric for one hour on a water bath and the s i l i c a was filtered off, ignited and weighed. The f i l t r a t e was made to volume in a volumetric flask. Calcium and Magnesium. Calcium and magnesium were determined ••in an aliquot of this solution. Iron and aluminium were sep-arated by the basic acetate method. Calcium was precipitated twice as oxalate and the final precipitate was dissolved in sulphuric acid and titrated against standard potassium per-manganate* The combined f i l t r a t e s from calcium precipitation were evaporated to a volume of approximately 150ccs* Magnesium was precipitated from the boiling solution with sodium ammonium phosphate as magnesium ammonium phosphate* This precipitate was f i l t e r e d off, ignited and weighed as magnesium pyro phos-phate. Fhosphoais. Phosphorus was determined in a separate aliquot by precipitation as ammonium phospho-molybdate, solution in ammonium hydroxide, and precipitation as magnesium ammonium phosphate. This precipitate was fil t e r e d off, ignited and weighed as raagnesium-pyro phosphates Potassium and Sodium. Potassium and sodium were also determin-ed in a separate aliquot by the standard chloroplatinate method. Iron. Iron was determined colorimetically in an aliquot by the potassium thiocyanate method. The basic acetate separation for iron and aluminium was used in spite of warnings against i t (80) because the precipitation of such small quantities of iron as are present in plant ash, as a hydroxide proved very d i f f i c u l t . (23) Ho trouble was experienced with the basic acetate method so i t was used exclusively. For carrying out the second part of the experi-ment, fifteen one year old apple trees were supplied by the Dominion Experimental Station, Summerland. A l l trees were of approximately the same size and external appearance and a l l were grown from root stock. Three of them were set aside for chemical analysis and the remaining twelve were used in the actual experiment. The trees were grown in five gallon earthenware jars. Covers for the containers were made of fibre board dipped in molten paraffin to maintain a certain degree of hardness. One tree was mounted to a jar and was suspended through the centre of a large cork f i t t e d into the cover. The contact be-tween the tree and the cork was loosely padded with absorbent cotton in order to permit free growth of the trunk. The culture solution employed was that used by Harris (24) and introduced by Hoagland• Its concentration and composition is as follows: K - 190 ppmv P0 4 - 117 ppm. Ca 172 ppm. S0 4 - 200 ppm. Mg - 52 ppm. Fe citrate 0,5% solution UQg - 700 ppm. when required. The culture solution was made up in 260 l i t e r lots and the solution in each jar was changed every three weeks. Aeration of the solution was accomplished by means of an apparatus shown in Fig. ' Water was run through a suction pump, and the air and water mixture discharged into (24) the reservoir. The water was run off at the side and sufficient air pressure was developed in the reservoir to produce a con-stant jet of air to each jar. Aeration was continued constant-ly from the beginning'to the end of the experiment. This type of apparatus proved very cheap and efficient for the purpose intended. •Bach •container.-was f i t t e d with a scale for measuring the volume of water transpired daily and i t was found necessary to add d i s t i l l e d water several times during the three week period, in order to maintain the volume of nutrient solution in the j ar. The method used to k i l l the root systems was to l i f t the tree out of the nutrient solution and expose the root to an air blast for a definite period of time. This a ir blast was produced by an electric fan six inches in diameter placed one foot from the root. This prodedure proved very satisfactory and could easily be applied for longer or shorter periods to obtain different degrees of root k i l l i n g . Samples of the roots were taken before and after exposure to the air blast in order to have some record of the degree of k i l l i n g accomplished. The twelve trees were divided into four groups of three trees each. The f i r s t group was given an exposure for five minutes, the second group for ten minutes and the third group for fifteen minutes. The fourth group received no ex-posure and was kept as a check. Fifteen minutes exposure caused almost a complete browning of the root system and in some cases wilting of the tops. The trees recovered quickly (25) upon reimmersion in the nutrient solution. Root k i l l i n g was carried on as the solutions were "being changed. For the f i r s t six weeks a l l trees were allowed to grow without any difference of treatment and at the end of that time a l l presented practically the same degree of growth and general appearance of health. As the trees were by that tirae in leaf, and had established vigorous new rootlet develop-ment, the f i r s t root k i l l i n g treatment was applied. Each group except the checks was exposed for the respective time periods mentioned above namely,. Group 1 - five minutes; Group 2 -ten minutes; and Group 3 - fifteen minutes, and then a l l were immersed in a fresh supply of nutrient solution. This proced-ure was carried on for eighteen weeks, the root k i l l i n g treat-ments and change of nutrient being applied once every three weeks. At the end of this time the experiment was concluded. The physical appearances of the trees at the conclusion of the experiment were widely different. The checks had by far the most healthy appearance, and had made consider-ably more growth than any of the treated trees. Two of the trees in the f i r s t group (these receiving five minutes exposure) had completely shed their leaves and had to a l l appearances passed into a dormart condition* A l l during the experiment, a,ny leaves that had dropped, or the branches that had broken, were collected and those from each tree were kept separately. At the end of the run each tree together with the accumulated fallen leaves etc. was dried and weighed separately. A separate chemical analysis TABLE If0.1 ANALYSIS OF FRUIT BUDS. 1932 Group Ho.l Group Ho .2 Group Mo.3 CaO MgO P2°5 SO-Fe 20 3 H"a20 Si0 o .02374 .01394 . 00516. .01338 .00380 *00010 .00110 .00047 .02290 .01182 .0043S; •01198 .00350 .00010 .00064 ^00031 .01753 .01582 .00488 .01465 .00380 .00009 .00120 .00032 Total Ask .07553 .07085 .07110 Expressed in grams per gram of dry material, Group Ho.! - Kelowna trees, diseased. tt " 2 - Summerland trees. • " 3 - Kelowna trees, normal. F r u i t Bucis r r> l if" O O s-1 • 4 I g>1 I S^J I E CD CD o j O O 33 ° I < — I I K (0 21 CO (M CO o o J (26) was then made on each, of the twelve trees. The methods used were the same as those described above. Analysis was made covering the entire tree roots, leaves, branches etc., a l l parts being mixed together for sampling. Results are shown in, Fig.^Sfc RESULTS. F i r s t Part. The d i f f i c u l t y in interpreting ihe results of the f i r s t part of the work, lies in estimating the significance of the variables known to be present in the samples. As men-tioned ab ove the Summerland and Peachland trees are growing under different s o i l and climatic conditions from those of Kelowna and also different from each other. In addition, cultural conditions in a l l four orchards have been varied to a certain extent in the past, and the degree of health of these orchards is a d i f f i c u l t matter to estimate especially in the case of the Summerland orchard where, while no Drought--Spot, Corky-core and Die-back were present, yet the occurrence of so much Collar Rot definitely points to a certain degree of unbalance* Analysis of the bud samples as shown in TableX shows a slightly higher ash content for the diseased trees than for those assumed to be healthy from Kelowna. This variation is hardly great enough to be significant. Variation also occurs between health and disease in the cases of one or two of the individual elements, n otably calcium, phosphorus and potassium, while an excess of calcium is found in the TABLE. - H 0 . - 2 AlfALYSIS OF TYfIG GROWTH 1933. Group S o i l Group Uo.2 Group Ho„3 Group Ho.4 H~ CaO KgO MgO s o 3 S i O o .0063? .01990 .00412 .00216 .O033S ,00150 ,00004 ,00076 •00044 .00585 .02260 .00431 .00215 .0026? .00224 .00005 ,00069 .00026 .00532 .01961 .00442 .00213 ,00350 .00150 .00004 .00068 .00029 .00628 .01670 .00367 .00219 .002&6 .00130 .00003 .00077 .00015 T. otal Ash .03930 .04750 .03710 .03710 Expressed in grams, per gram of dry material. Group Ho.1 « » 2 » « 5 « » 4 KelaTsna* trees, diseased. Summerland trees* PeacHland trees. Kelowna trees, normal. (27) diseased trees the other tv/o minerals are present in smaller amounts than in the normal trees. Analysis of the tv/o year old twig growth as shown in Tableji shows a higher ash content for the trees of Groups No. 1, 2 and 3 than for the normal trees of Group Bo.4. This is especially marked in the case of the Summerland trees Group No.2. This higher percentage of minerals is reflected in an increased amount of some of the individual elements especially calcium, phosphorus, potassium and iron. In fact, most of the elements w i l l be noted to be higher in the diseased trees than in the normal trees. However, in view of the fact that the Group No.2 trees, while they are known to be in a certain degree of un balance, s t i l l have not yet evinced actual symptoms of the disease in question, the significance of this variation amy reasonably be considered questionable, especially as the varia-tions are most marked in the case of this group. Of course these variations may be characteristic of the climatic and s o i l conditions rather than the actual absorption of the trees them-selves , in which case this characteristic would either act to increase any variation caused by physiological disease, or else to reduce i t , or even to reverse i t . Unfortunately no analyses have been made on either perfectly normal trees from Summerland or on trees from this d i s t r i c t definitely affected with these disorders. Actually the best basis of comparison lies between Groups No.2 and No.4. Both', these groups were grown under the same s o i l and climatic conditions. Group No. 3 was T A B E S HO. 5 H Ca E 3% P S Fe Ha Si 1HALYS1S OF THSBS 1935 Group Ho.l Group Ho.2 Group Ho.3 Group Ho.4 .01254 .01445 .01758 .01721 .01234 .01077 .00161 .00460 .00230 .00095 .00079 .00034 .01227 .01579 .00189 .00445 .00210 .00083 .00082 .00031 .01706 .01189 .00189 .00703 .00200 .00085 .00093 .00029 .01066 .01101 *00150 .00395 .00160 .00059 .00097 .00043 Total Ash .0550 .0598 .0708 .0481 Expressed in grams per gram of dry material. Group H o . l it is 2 » » 5 » n 4 Five minute rootlet k i l l i n g . Ten il' * tt Fifteen 1* n w GHeek. (28 ) included in the analyses as characteristic of a diseased con-dition resulting from excess amounts of moisture in the s o i l * The similarity between the composition of these trees, and that of the trees of Group ITo • 4 which are suffering from the same disorders as a result of the prolonged period of drought, is very interesting* Second Part Analyses of the small trees grown in liquid culture yielded somewhat similar results to those obtained from the twig analysis in the f i r s t part. The most conspicuous indication of an unbalance is the increased ash content of the treated trees. As noted in Fig-HT the percentage of mineral nutrients in the tissue of the treated trees is distinctly higher, especially in the Group. Ho- 3 trees. This increase in mineral content is apparently-most pronounced in the case of calcium and iron, although the potassium, phosphorus and sulphur contents are to a certain degree higher also. It was noticed in the beginning that the original nutrient solution contained too l i t t l e iron for proper growth and a l l the trees developed the typical chlorotio conditions of an iron deficiency. Accordingly the concentration of the iron was stepped up, unfortunately to such an extent that some bufning of the foliage was apparent, and some kil l i n g of the roots of even the checks took place. However, in the face of this unfavourable environment the checks were able to exclude the excess iron to a very marked degree, and absorption of (29) this mineral took place only slightly higher than usual, while with the treated trees practically a l l the iron in the solution was absorbed in almost every case as determined by analysis, of solution and the effect on the foliage and roots was very mark-ed. It is noticeable that at the end of the experiment, the concentration of iron per gram of dry weight in the treated trees was higher by one hundred per cent than in the checks. This fact seems very indicative of an indiscriminate absorp-tion of minerals by an injured root system. Only in the cases of s i l i c a , sodium and nitrogen were the concentrations of any of the elements higher in the check trees. S i l i c a and sodium are not of relative importance in the metabolism of the tree, and in any case, the excesses of these minerals are too slight to be of any significance. That nitrogen is high in the checks is to be expected as a result of the increased rate of metabolism taking place in the leaves of the check trees. In general, i t is apparent from these analyses that by injuring the root system we can induce a greater mass flow of minerals into the growing plant. This is especially to be noted in the case of calcium and iron, although within certain limits i t can be extended to most of the other essent-ialelements. Suggested Significance of Results The results reported in this paper raise the question as to whether nutritional conditions dn trees, attrib-uted by many investigators to fe r t i l i z e r s , soil conditions and ( 3 0 ) other external physical agencies, are not in reality due to injured root systems. If the ab i l i t y of the tree to absorb ^ food materials from the s o i l is so dependent upon the physical condition of i t s absorbing tissue, then the results of f e r t i l -izer treatments w i l l be influenced by the condition of the absorbing system of the tree. Just how common is this unbalance of absorption in trees? The evidence seems quite clear that Drought-spot, Corky-core and Die-back are occasionally present in every orchard growing section in Canada, for these disorders have been found in Quebec, Ontario and 11 ova Scotia, as well as in B r i t i s h Columbia. The presence of Drought-spot and Corky-core in numerous apple growing di s t r i c t s , suggests that under so-called normal cultural conditions a certain amount of root k i l l i n g with the resultant unbalance absorption of food mater-ia l s may possibly be widespread as tbe cause of the disorders. Our results, moreover, suggest that an unbalanced absorption does n ot necessarily express i t s e l f in the form of Drought-spots Corky-core and Die-back, but may become evident in some other physical weakness in the trees, such as the high percent-age, of Collar Rot present in the orchard from which the Croup Fo. 2 trees were selected. It i s quite reasonable to suspect that many so called off colour, poor vi t a l i t y trees are simply an expression of a certain degree of unbalanced absorption rather than an expression of lack of f e r t i l i t y in the s o i l . SUMMARY. 1. Samples of the f r u i t "buds, and of the two year old twigs of both healthy and diseased Mcintosh apple trees, grown in the Okanagan, have been analyzed for their mineral content. 2. Small two year old apple trees grown in water culture have been exposed to root k i l l i n g treatments, and the tissue of treated and untreated trees growing under the same con-ditions has been analyzed for i t s mineral content. 3 . Ash analyses of the f r u i t buds have shown a slightly higher ash content for the diseased trees. Calcium has been found to be higher in diseased trees, while phosphorus and potassium have been found to be lower. 4 . Analyses of diseased two year old twigs, have shown a higher ash content for diseased trees. The higher content is reflected especially in the oalcium and iron contents a l -though some of the other minerals are also slightly higher. 5. Analysis of small trees grown in water culture, has shown a distinctly higher ash content for trees with injured root systems. Calcium and iron are most significantly higher, but most of the other minerals are higher also. 6. Suggestions are made regarding the significance of the results. ACE1T0 wTJEDGEKENT . The writer wishes to express his appreciation of the suggestions and guidance given by Dr. H.R. Mccarty and Mr. J.C. Roger of the Dominion Field Laboratory of Plant Pathology at Summerland in the planning and execution of this experiment. Thanks are also due to Mr. R .G. Palmer of the Experimental Station at Summerland for his assistance and helpful criticisms. KBBEKESTCgS. 1. Alben, A.O., Cole, J.R. and Lev/is, R.D, Chemical Treat-ment of Pecan Rosette.- Phytopathology, Vol.22. 1932. 2. Allyn, W.E.. The Relation of lime to the Absorption of Iron by Plants. Proc. Indianna Ac.of Sci., Vol.37,1927. 3. Anderssen, F.G-. Chlorosis of Deciduous Pruit Trees Due to a Copper Deficiency. Jour.of Pom. and Hort. Sci. Vol.X. 1932.' 4. Methods of Analysis. Ass. of O f f i c i a l Agr. Chemists 1930. 5. Bartholomews E.T. Barrett,J.T. and Pawcett, H.S. Internal Decline of Lemons I. Amer.Jour.Bot.Vol.10,1923. 6. Internal Decline of Lemons II.Amer.Jour. Bot.Vol.10. 1923. 7i ^ Internal Decline of Lemons 111.Amer. Jour.Bot.Vol.13. 1926. 8. . and Robbins, W.J. Internal Decline of Lemons TV. Amer. Jour. Bot. Vol. 13. 1.926. 9. Bennett, J.P. The Treatment of Lime Induced Chlorosis with Iron Salts. Univ. of Calif., Agr.Exp.Stat.Circ.321 1931. 10. Blackman, V.H. Osmotic Pressure.Root Pressure and Exudation. Uew Phytol. Vol.20. 1921. 11. Brenchley, W.E. Inorganic Plant Poisons and Stimulants 1914. 12. CameW.M. Exanthema. West.Aust.Dept.Agric.Leaflet 176 13. Pittman, H.A. and H.G. E l l i o t . Bitter Pit of Apples in Australia. Bui1.41. Australia 1929. 14. Conner a, S.D. The Injurious Effect of Borax in F e r t i l -izers on Corn. Proc. Ind.Acad.Sci.1917. 15. Daubeny, C.G.B. On the Power Ascribed to the Roots of Plants of Rejecting Poisonous or Abnormal Substances Presented to them. Jour.Chem.Soc.Vols. 14 & 15. 1862. 16. Floyd,. B.F. Some Cases of Injury to Citrus Trees Apparent-l y Induced by Ground Limestone. Fla.Agr .Exp.Stat.Bull. 137. 1917* 17. Fisher, D.F. Cork Spot of Apples. Vfenatehee Fruit Grower. April 1923. 18. Garner, W. , McMurtrey, J.E., Bacon, C.W., and Moss,E.G. Sand Drown, a Chlorosis of Tobacco Due to Magnesium Deficiency and the Relation of Sulphates and Chlorides of Potassium to the Disease. Jour.Agr.Res.,Vol.23. 1923. 19. Gilbert, B.B. McLean,F.T., and Adams, W.F. The Current Mineral Nutrient Content of the Plant Solution as an In-dex: of Metabolic Limiting Conditions. Plant Physiol. Vol. 2. 1927. 20. Gildehaus, E.J. The Relation of Nitrogen to Potassium in the Nutrition of Fruit Trees. Bot.Gaa.No.4. 1931. 21. G i l e s P.L. Relation of Calcareous Soils to Pineapple Chlorosis. Porto Rico Agr .Exp.Stat .Bull.11. 1911. 22. 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The Effects of Kanurial Treatments on the Chem-i c a l Composition of Gooseberry Bushes. Jour.Pomol. and Hort. Sci. Vol.VII. Hos.l & 2. 1928. 78. . Experiments on the Manuring of Fruit Trees III Jour.Pomol. and Hort. Sci.Vol.VIII. 1930. 79» Chem. Investigations Relating to Potassium Beficiency of Fruit Trees. Annual Report Agr. and Hort. Res. Stat. Univ. of Bristol. 1931. 80. Washington, H.S*. The Chemical Analysis of Rocks. 1930. 


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