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Transpiration and stomatal movements of plants treated with sulphur dioxide Dill, Charlotte Elva 1939

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TRANSPIRATION AND STOMATAL MOVEMENTS OP PLANTS TREATED WITH SULPHUR DIOXIDE by C h a r l o t t e S i v a D i l l A T h e s i s s u b m i t t e d f o r the Degree of MASTER OF ARTS i n the Department of BOTANY The U n i v e r s i t y of A p r i l , B r i t i s h 1939 Columbia AGKFOWLEDQ'BIffl¥TS » To Dr. A.H. Hutchinson I am very g r a t e f u l f o r h i s assistance i n t h i s work, f o r h i s advice i n the i n t e r p r e t a t i o of r e s u l t s , and f o r the use of the equipment necessary. To Dr. P. Dickson I wish to express my appreciat-i o n f o r help and advice i n growing the plants and s e t t i n g up the apparatus and f o r suggestions of references and methods of obtaining data. To the f o l l o w i n g I am also deeply indebted. To Mrs. Miles R i t c h i e , who was o r i g i n a l l y to have shared i n t h i s workj, f o r cooperation i n s e t t i n g up the f i r s t experiment and making the f i r s t weighings. To Dr. Dickson and Mr. J.D. Menzies f o r bringing s o i l from the greenhouse. To the' Agronomy Department f o r seeds. To the Chemistry Department f o r the use of a wet t e s t meter. To Mr. A. L i g h t h a l l of the C i v i l Engineering Department f o r the use of a planimeter. TABLE OF CONTENTS. A c knowiedg erne n t s. Statement of the problem................ .. . 1 Methods. The p l a n t c a b i n e t s and method o f s u l p h u r d i o x i d e treatment and analysis...................».0« 3 The plants used and methods of growing them .....0.«>. 7 Measurement of l e a f area Barley . ........... 12 Beans .....p..........©.***.................. 13 Examination of atomata. Barley «> 14 Beans .....................<....».........»..<> 16 Method of t r e a t i n g d a t a 17 Data. P l r s t Experiment: h i s t o r y , environment records and appearance of p l a n t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Second Experiments h i s t o r y , environment records and appearance of p l a n t s . . . . . . . . . . . . . . . . . . . . 20 T h i r d Experimenti history., environment records and appearance of plants 22. Eo-urth. Experiments h i s t o r y , environment records and appearance of plan t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Tables and graphs of t r a n s p i r a t i o n measurements ...» 26 Tables and graph of a t o m a t a l measurements........... 34 TABLE OF CONTENTS (continued) D i s c u s s i o n of r e s u l t s 36 C o n c l u s i o n s 41 Summary. 43 B i b l i o g r a p h y . 44 TRANSPIRATION AND S.IOMATAL. MOVEMENTS OE PLANTS r TREATED WITH SULPHUR D I O X I D E . STATEMENT OE THE PRO BLEU. The problem of the e f f e c t of s u l p h u r d i o x i d e gas on the f u n c t i o n s of p l a n t s has been approached In t h i s paper from the. p o i n t of view of I t s e f f e c t on t r a n s p i r a t i o n c o r r e l a t e d w i t h the opening and c l o s i n g of the stomata. While t r a n s p i r a t i o n ^ as a p h y s i o l o g i c p r o c e s s may or may not have any v e r y g r e a t p r i m a r y f u n c t i o n i n the l i f e of a p l a n t 5 n e v e r t h e l e s s measurements of the amount of t r a n s p i r a t i o n c a r r i e d on by a p l a n t serve as one i n d e x of a p l a n t *s a c t i v i t y , and ser v e as an i n d i c a t i o n o f the degree o f atoBiatal opening.. The degree of s tornate1 opening I s o f a c t u a l s i g n i f i c a n c e i n c o n n e c t i o n w i t h the amount of photo-s y n t h e s i s b e i n g c a r r i e d on. Maximow and Krasnoss e l s k y -maximovr (.11) have e x p e r i m e n t a l l y c o r r e l a t e d photosynthesis«, t r a n s p i r a t i o n and s t o m a t a l openings. There I s c o n s i d e r a b l e disagreement among those who have worked on the problem o f I n v i s i b l e I n j u r y r e g a r d -i n g the v a l i d i t y of the t h e o r y t h a t s u l p h u r d i o x i d e has d e t r i m e n t a l e f f e c t s on p l a n t a v/hen p r e s e n t i n c o n c e n t r a t i o n s t h a t do not cause v i s i b l e i n j u r y . W i e l e r (16.) found t h a t i n 3-10 y e a r o l d p i n e s , spruce and c e r t a i n hardwoods the - 2 -a a s i i a i l a t i o n of carbon d i o x i d e was reduced, a t d i l u t i o n s , below those n e c e s s a r y to d i s c o l o r the l e a v e s . However the c o n c e n t r a t i o n he mentions I s v e r y h i g h , 2 p.p.m. r and would cause v i s i b l e i n j u r y to such p l a n t s as legumes and g r a i n s . On the o t h e r hand, Thomas and H i l l (15) working an. the r e l a t i o n o.f s u l p h u r d i o x i d e i n the atmosphere to p h o t o s y n t h e s i s and r e s p i r a t i o n i n a l f a l f a , found t h a t con-c e n t r a t i o n s , w h i c h produced no v i s i b l e i n j u r y a l s o d i d not cause, i n v i s i b l e i n j u r y . The papers of Katz. and Ledingham ar e n o t a v a i l a b l e but have been quoted by S e t t e r s t r o m et a l . (13) to the e f f e c t t h a t t h e i r work s u b s t a n t i a t e s t h a t of Thomas and F i l l . S e t t e r s t r a m 9 Zimmerman and C r o c k e r (13) made I n v e s t i g a t i o n s on the e f f e c t of low non-marking con-centra.tia.ns of sulphur- d i o x i d e on the y i e l d of a l f a l f a and C r u c i f e r a e when grown i n v a r y i n g c o n d i t i o n s o f m o i s t u r e and n u t r i e n t s u p p l y . They found t h a t the low c o n c e n t r a t i o n s used had no s i g n i f i c a n t e f f e c t on the y i e l d of e i t h e r a l f a l f a or the species, of C r u c i f e r a e s and i n one experiment they found a s i g n i f i c a n t I n c r e a s e i n the sulphur' c o n t e n t of the l e a v e s . I n v e s t i g a t i o n s on the nature and cause o f v i s i b l e i n j u r y by s u l p h u r d i o x i d e have shown t h a t the degree of i n j u r y I s dependent upon the c o n c e n t r a t i o n s ^ d u r a t i o n of exposure and the h u m i d i t y o f the a i r ( 6 ) . A c c o r d i n g to Zimmerman and Crocker ( 1 7 ) h u m i d i t y i s a f a c t o r because of i t s e f f e c t on the stomata. They found t h a t w i l t e d p l a n t s are more r e s i s t a n t than t u r g i d ones, and a t t r i b u t e the r e s i s t a n c e to. the f a c t t h a t the stomata a r e c l o s e d . The f a c t t h a t p l a n t s a r e more r e s i s t a n t a t n i g h t than i n d a y l i g h t supports t h i s i d e a . Sulphur d i o x i d e i s be l i e v e d , to a c t through the stomata i n c a u s i n g v i s i b l e i n j u r y and t h e r e i s a p o s s i b i l i t y t h a t It. might a c t upon the • guard c e i l s thus a f f e c t i n g the s I z e of the stomata. I f t h i s were t r u e i t would be an e x p l a n a t i o n o f the reduced a s s i m i l a t i o n o f carbon d i o x i d e s t a t e d to; have been found by some workers„ I n the work of Y/.E. J a c k (7) low non-marking c o n c e n t r a t i o n s o f s u l p h u r d i o x i d e were found to reduce the amount of t r a n s p i r a t i o n s i g n i f i c a n t l y y and the p r e s e n t experiment was undertaken w i t h a view to c o r r e l a t i n g any r e d u c t i o n i n t r a n s p i r a t i o n , w h i c h might o c c u r , w i t h the stomata! openings o f the p l a n t s . ~4-METHODS. Tlie plant cabinets and method of sulphur dioxide treatment and a n a l y s i s . The plants were grown In cabinets under a r t i f i c i a l l i g h t . The two .cabinets, one f o r sulphur dioxide treatment and one f o r c o n t r o l , are Identical. I n co n s t r u c t i o n except f o r the sulphur dioxide i n l e t and mixing chambers on one. The cabinets are constructed according to the plan of Davis and Hdagland ( 2 ) , except that the l i g h t s are d i r e c t l y above the p l a n t s , as suggested by Swain and Johnson (14), and that i n the base of each cabinet i s a water tank f o r the purpose of i n c r e a s i n g the r e l a t i v e humidity of the atmos-phere. Each cabinet i s composed of a base 6 f e e t long by 2. f e e t wide by 2. f e e t h i g h i n which the c u l t u r e j a r s are placed on wooden frames. Above t h i s i s a. glass, walled cover 6 f e e t long by 2 f e e t wide by 5 f e e t h i g h which can be r a i s e d and lowered to allow easy access to the p l a n t s . When lowered i t i s fastened i n place and the cabinets are p r a c t i c a l l y a i r t i g h t . The l i g h t s are seated i n 52 cm. r e f l e c t o r s w i t h the bulb centres 9 inches above the cabinet tops. The height of the l i g h t s above the l e v e l of the s o i l i s 5^ - f e e t . Owing to the extreme heat produced by the l i g h t s the gl a s s tops are kept covered w i t h about one h a l f to one inch of water to absorb the heat. The l i g h t s are c o n t r o l l e d by a time switch. A. continuous c i r c u l a t i o n of a i r through the cabinets i s . maintained by two Sirocco blowers, driven by General E l e c t r i c motors. The sulphur dioxide was introduced to the exper-;Imental cabinet through a g l a s s tube entering the a i r intake pipe. The a i r w i t h the sulphur dioxide then passed through a large galvanized i r o n box containing b a f f l e plates ?/here the gases were thoroughly mixed before entering the plant cabinets. The a i r enters the plant cabinets at the bottom, i s d i v e r t e d by b a f f l e p l a t e s i n the base and passes up through the wooden frames supporting the p l a n t j a r s . The a i r passes out through a pipe at the top. The sulphur dioxide was obtained from the Ansul Chemical Company, Marinette, Wisconsin. The 6 pound c y l i n d e r s * containing l i q u i d sulphur d i o x i d e , are equipped w i t h a needle valve to regulate the flow o f gas., Erom the valve c a p i l l a r y tubing- leads i n t o a r e s e r v o i r of l i q u i d petrolatum, through which the gaa bubbles r i s e . Glass tubing leads from t h i s point through the w a l l to the adjacent room where i t enters the a i r intake to the plant cabinet. Counts of the number of gas bubbles per minute give a rough estimation of the amount of gas being emitted to the cabinet. The method used to determine the exact concentrat-i o n of sulphur dioxide In the cabinet was that of G r i f f e n and Skinner ( 5 ) . By means of a s u c t i o n pump a gram molecular volume of a i r from the pla n t chamber i s bubbled through an absorber c o n t a i n i n g 100 e.c. of a s o l u t i o n c o n t a i n i n g i o d i n e , potassium iod i d e and s t a r c h . Through a-second absorber i s bubbled the same volume of a i r which has passed through a soda-lime tower. The s o l u t i o n s are then drawn o f f i n t o f l a s k s and t i t r a t e d to the same l i g h t blue end point with .001 N. sodium t h i o s u l p h a t e , u s i n g a p r e c i s e 5 c c . burette with readins to .02 c . c . The d i f f e r e n c e between the two readings equals the equivalent of the sulphur dioxide absorbed, The flow of a i r through the absorber was regulated by a small pressure e q u a l i z i n g tank, and was measured by a U-manometer through which the a i r passed before e n t e r i n g the absorber. The manometer was c a l i b r a t e d with, a wet t e s t meter which had been p r e v i o u s l y c a l i b r a t e d by passing through i t , a known volume of a i r from a large a s p i r a t o r . The volume of a i r was forced from the a s p i r a t o r through the wet t e s t meter by water from the tap. The apparatus was f i n a l l y adjusted to pass 22.4 l i t r e s of a i r through the absorbers . i n a d e f i n i t e i n t e r v a l of time and the manometer reading f o r t h i s r a t e was recorded. The temperature and r e l a t i v e humidity were recorded but not c o n t r o l l e d . Owing to the proximity of the l i g h t s the temperature v a r i e d g r e a t l y , r i s i n g to about 90' P. at the end of the l i g h t p e r i o d and f a l l i n g to room temperature during the period of'darkness. The v a r i a t i o n i n temperature caused a d i u r n a l v a r i a t i o n i n r e l a t i v e humidity which f e l l during the l i g h t period and rose during the dark period. During the l a s t experiment an attempt was made to c o n t r o l the humidity by the i n s t a l l a t i o n of a humidistat i n each cabinet. Each humidistat was connected to a heating element i n the water tank i n the base of the cabinet, iihen the humidity f e l l below the desired percentage the heating element was switched on automatically causing the water to evaporate more f r e e l y thus increasing the humidity. When the humidity rose the element was switched o f f . This method was f e a s i b l e during the period of darkness when the temperature remained f a i r l y constants but during the period of l i g h t the temperature rose above 90'E. causing a drop i n the r e l a t i v e humidity which could not be overcome by the evaporation of water using t h i s apparatus. This means of changing the humidity has an excessive l a g period i n i t s r e a c t i o n to the humidistat and does not give s a t i s f a c t o r y c o n t r o l of the r e l a t i v e humidity, .however, the readings f o r the two cabinets agree reasonably w e l l , so that the co n d i t -i o n s were s i m i l a r and the v a r i a b l e f a c t o r s were p a r a l l e l except f o r the presence of sulphur dioxide I n one. The p l a n t s used and method of growing them* ihe plants used f o r the f i r s t and second exper-iments were D u c k b i l l b a r l e y , a pure l i n e of seed and selected f o r u n i f o r m i t y of growth, obtained from the department of Agronomy, of the U n i v e r s i t y , and two v a r i e t i e s of dwarf beans f o r tne 3rd. and 4th experiment, B r i t t l e Wax i n exper-- a -iment 3 and Masterpiece i n experiment 4» A quantity of r i c h loam s o i l s u f f i c i e n t f o r the experiment was obtained from the U n i v e r s i t y greenhouse. I t was w e l l mixed to insure u n i f o r m i t y . The water holding cap-a c i t y of t h i s s o i l was then determined. Aluminum cups w i t h perforated bottoms, l i n e d w i t h f i l t e r paper were used f o r the s o i l samples. Ten siamples of s o i l were d r i e d to- constant weight at 103'G. The cups were then immersed i n water t o the l e v e l of the s o i l w i t h i n and water allowed to saturate the s o i l . They were then allowed to d r a i n u n t i l a l l the surplus water had dripped o f f , and they were then weighed. Evapor-a t i o n from the surface was prevented by p l a c i n g a large watch glas s on top of each cup. The water holding capacity of the s o i l was. found to be 8Q95% of the dry weight of the s o i l . The- s o i l moisture used i n these experiments was one h a l f the water holding capacity of the s o i l or 40^ of i t s dry weight. In preparing the j a r s f o r the p l a n t s a s u f f i c i e n t q u a n t i t y of s o i l was thoroughly mixed to insure uniform s o i l moisture. The j a r s , two quart Mason j a r s w i t h wide mouths, which (with the watering apparatus to be described below), had been p r e v i o u s l y weighed, were f i l l e d w i t h s o i l which was tapped down to prevent l a t e r s e t t l i n g . At the same time ten samples of s o i l were taken and weighed, then d r i e d to constant weight to determine the water content of the s o i l at the time* Immediately a f t e r f i l l i n g , the j a r s were weighed, and assuming the wateE content of the s o i l to be uniform, the dry weight of the s o i l I n each j a r could be c a l c u l a t e d from the value determined f o r the s o i l samples. A base weight was then c a l c u l a t e d f o r each j a r to bring the water content to 50$ of the water holding capacity of the s o i l . Since the experiment was an attempt to f i n d the r e l a t i v e amounts of water transpired by two groups of p l a n t s , i t was necessary to prevent evaporation from the surface of the s o i l and at the same time to have a means of watering the p l a n t s * The method used by Kiesselbach (8, p.50) was adopted w i t h s l i g h t m o d i f i c a t i o n s . A small inverted flower pot was placed i n the bottom of the j a r . A piece of f i n e g l a s s tubing was attached to the side of a t h i s t l e tube w i t h e l a s t i c bands, and the two tubes were i n s e r t e d through the hole i n the flower pot wi t h the t h i s t l e tube extending nearly to the bottom of the j a r and the side tube ending about one h a l f i n c h w i t h i n the hole. The lower e l a s t i c band p r o j e c t i n g around the tube was s u f f i c i e n t to keep them i n place i n the flower pot. The top of the t h i s t l e tube was f i t t e d wi t h a rubber stopper and the side tube l e f t open. When the j a r s were f i l l e d and the s o i l covered wi t h wax, water could be added through the t h i s t l e tube and the a i r escaped through the side tube. L i k e w i s e , as water was transpired by the plants a i r was drawn i n through the side tube. Check j a r s were prepared to t e s t the evaporation of water. The l o s s of water per j a r averaged 1.1 gm. over a peri o d of f i f t y days and the i n d i v i d u a l r e s u l t s were i n close «L0-> agreement* Th.erefo.re no c o r r e c t i o n was considered, to be necessary f o r water l o s s from the cultu r e j a r s . Owing to the d i f f e r e n c e i n structure between barley and beans d i f f e r e n t procedures were followed from the time of p l a n t i n g * The barley seeds, which had been germinated f o r three days, were selected f o r uniform germination and planted f i v e to a j a r . The surfaces of the j a r s were then covered to a depth of approximately 2 m.m. w i t h a wax mixture of three parts petrolatum and seven parts p a r a f f i n i n the 1st experiment. The proportions were l a t e r changed to four of petrolatum and s i x of p a r a f f i n . This i s the method described by Briggs and Shantz; ( l ) . The barley c o l e o p t i l e s pierced the wax covering i n about two days and growth i n the j a r s appeared to be normal. I n the f i r s t experiment the percentage of plants to f i n i s h germinating was low, due, probably, to l a c k of s u f f i c i e n t oxygen while germinating. I n the second experiment f o u r holes were punched i n the wax s e a l of each j a r . These were again sealed over a f t e r the seedlings had come through the x?ax. I n t h i s case there was p r a c t i c a l l y 1 0 0 $ germination of the seedlings. The j a r s were weighed two to three times per week and were brought to t h e i r base weights by the a d d i t i o n of water. The scales used had a capacity of 4-g- kilograms and were s e n s i t i v e to one f i f t e e n t h of a gram. The t o t a l weight o f a j a r was approximately 2 4 0 0 gm. and the j a r s were weighed to .1 gm.. The beans were planted four to a j a r . Owing to the large cotyledons the jar s could not be waxed over immediately f o l l o w i n g p l a n t i n g . The plants were allowed to grow u n t i l the s t a l k had r a i s e d the cotyledons w e l l above the s o i l , then they were thinned to•the three best plants per j a r i n the t h i r d experiment and the two best i n the f o u r t h experiment. The par-a f f i n and petrolatum mixture was then poured over the surface at a temperature of between 45' and 50'C.. The large l e a f area of the bean plants caused a great l o s s of water so during the t h i r d experiment the jar s were weighed and watered on a l t e r n a t e days and d e f i n i t e q u a n t i t i e s of water were added oh the i n t e r -vening days. In the f o u r t h experiment the j a r s were weighed and watered d a i l y except f o r a few occasions on which d e f i n i t e q u a n t i t i e s were.added. In both the experiments on beans i t was found that a large percentage of the plants permanently w i l t e d when they were about four weeks o l d . In a l l cases every plant i n a p a r t i c u l a r j a r w i l t e d . In no case d i d one plant In a jar w i l t while others remained normal. When the w i l t e d plants were examined, i t was found that the root systems had hot developed a p p r e c i a b l y and no root nodules were.found on them. A growth of mold was found immediately below the wax cover and i n some cases the bean stem had r o t t e d j u s t below the s u r f a c e . When healthy plants were ex-amined the root system was found t o be extensive and covered with root nodules. A growth of mold was found i n these jars a l s o but i t was more extensive i n the jar s i n which the plants had wilted.> The mold apparently attacked the "bases of the stems of those plants which w i l t e d but caused no serious e f f e c t s on those plants which survived. There may also have been some In j u r y to the plants caused by the heat of the wax when i t was a p p l i e d . Those plants which d i d not w i l t when f a i r l y young remained healthy u n t i l the end of the experiment. Therefore to obtain uniform m a t e r i a l the plants which showed no s i g h of w i l t i n g a f t e r a few weeks were selected and evenly d i s t r i b u t e d among those to be treated and those to serve as c o n t r o l s . Measurement of l e a f area. Barley. Ta obtain accurate comparisons of the amount of water tra n s p i r e d i t was necessary to obtain the l e a f area of the p l a n t s . To measure i n d i v i d u a l l y by graph paper or by a planimeter, the area of every l e a f would take too long? so an easier method was sought. The method of comparing the weight of pieces of l e a f of known area w i t h the weight of a l l the leaves was not used because the leaves vary a great deal i n thickness and therefore i n weight compared to area. Graf-Marin (4) found that there i s a c o r r e l a t i o n between the area of barley leaves and the product of t h e i r lengths times .widths. His method was used i n t h i s experiment. A number of leaves of a l l siz.es were placed under a transparent sheet of c e l l u l o i d and t h e i r o u t l i n e s traced w i t h a planimeter, which had been p r e v i o u s l y checked w i t h known areas to determine the accuracy of the instrument. The areas obtained were p l o t t e d on a graph ( J i g . l ) w i t h the products of t h e i r length times width. The values were found to f a l l e i t h e r side of a s t r a i g h t l i n e w i t h i n a small distance. The f a c t o r for convert-i n g the product of the length times width to the area was found to be .70, wit h v a r i a t i o n s between .556 and .890. The area, of the stems was obtained by measuring the length and taking an average diameter about the middle of the stem. The area was then c a l c u l a t e d . To make sure that the leaves measured had a c t u a l l y been f u n c t i o n a l , a l l dying leaves were removed from the plants previous to the second l a s t weighing and a l l the leaves, l e f t on were measured a f t e r the f i n a l weighing. Beans. Two methods were used to obtain the l e a f area. Samples of leaves were weighed and measured by the planimeter. Then the t o t a l weight of the leaves of a plant was compared w i t h that of the measured sample and the t o t a l area c a l c u l a t -ed. The sample was selected to contain representative s i z e s and. textures of leaves. The other method was to c o r r e l a t e the l e a f area wi t h the length. Graphs were made of terminal and l a t e r a l leaves of both v a r i e t i e s . ( F i g s . 2-5). The points on the graphs i n each case were found to f o l l o w a curve, the curves i n each of the four cases being s l i g h t l y d i f f e r e n t . These graphs were used to f i n d the l e a f area of the pl a n t s from "J5 1 0 l ' : 5 ~~ "25 " 25 " 3 0 Area of leaves i n :sq. icm„ -14-the Bieaaur.em.ents of the lengths of the leaves. In some cases "both the above methods were used on the same plants and were found to oheclc w i t h i n l i m i t s approximating "Sfo. Examination of stomata. Barley. For counting the number of stomata i n d i f f e r e n t areas, pieces of the leaves and stems were f i x e d i n a s o l u t -i o n of absolute a l c o h o l and acetic: a c i d , placed on a s l i d e and eslamined under the microscope. Ebr determining the degree of opening, the method of L l o y d (9) was used, t h a t of s t r i p p i n g the epidermis and plunging i t immediately i n t o absolute a l c o h o l . The theory behind the method i s that the absolute a l c o h o l dehydrates the c e l l u l o s e so q u i c k l y that there Is not time f o r the c e l l s to change t h e i r shape before the c e l l u l o s e i s hardened and therefore the stomatal opening remains f i x e d . Absolute a l c o h o l f i x a t i o n cannot be used f o r whole leaves because there i s s u f f i c i e n t water i n the mesophyll to d i l u t e the a l c o h o l and prevent the immediate hardening of the epidermal c e l l s . L o f t f i e l d (10} made comparisons of leaves f i x e d by t h i s method with, leaves examined while a l i v e and s t i l l attached to the p l a n t and found that the two methods gave s i m i l a r r e s u l t s . The w r i t e r assumed f o r purposes of t h i s experiment that Lo-ftfIelcL rs r e s u l t s were c o r r e c t . To make the stomata more c l e a r l y v i s i b l e the s t r i p s are stained i n Congo Red, a saturated s o l u t i o n i n absolute a l c o h o l , f o r a day before -15-examining,* They may be examined i n a b s o l u t e a l c o h o l , or a c c o r d i n g to L l o y d the s l i d e s may be made permanent by p a s s i n g the t i s s u e through c l o v e o i l and mounting i n Balsam, I t i s d i f f i c u l t to o b t a i n a l a r g e p i e c e o f b a r l e y e p i d e r m i s due to the r i d g e s and p a r a l l e l d e p r e s s i o n s on i t s -s u r f a c e . The upper s u r f a c e i s - so d e e p l y r i d g e d t h a t a l l attempts to o b t a i n the e p i d e r m i s r e s u l t e d i n o b t a i n i n g shreds o f v a s c u l a r bundles w i t h the epider m i s above them o n l y . The stomata l i e i n l o n g i t u d i n a l d e p r e s s i o n s between the bundles: and t h i s p o r t i o n o f the ep i d e r m i s d i d not come o f f when s t r i p p e d . For t h i s r e a son the lower s u r f a c e was used f o r a l l the samples because the r i d g e s a re not a s l a r g e and the ep i d e r m i s c o n t a i n i n g the stomata can be s t r i p p e d ' o f f . A s h a l l o w c u t was made a c r o s s the l e a f w i t h a sharp s c a l p e l and a s m a l l p i e c e o f the epi d e r m i s was r a i s e d . The p i e c e of e p i d e r m i s was then grasped by the f o r c e p s , s t r i p p e d down the l e a f and w i t h the same movement o f the hand plunged I n t o a v i a l of a b s o l u t e a l c o h o l . I n examining the s t r i p , stomata i n the p o r t i o n f i r s t r a i s e d by the s c a l p e l were not measured. The l e a f samples taken were the second youngest l e a f i n each case, to be sure t h a t the stomata were mature and s t i l l f u n c t i o n i n g . Samples were taken from the t r e a t e d and c o n t r o l p l a n t s a t i n t e r v a l s throughout the day. -16-• Transverse measurements were ma.de of s e v e r a l stomata w i t h a f i l a r micrometer. The s i z e s were d i v i d e d i n t o s i x groups as f o l l o w s : S'X_2L.G 0 o- & c* G J - . O S G C L » S i s E 1 e « » & u.p "to 1 &.(5x1 & S-X. Zt.& & & & o -1- © "fc.o 3 p Qui. ©. S o l to 4 . 4u . S i z e 4 « .«,. 4,5 to 5.8u» I t was found t h a t the stomata c o u l d he p l a c e d i n these s i s e groups q u i t e a c c u r a t e l y , by j u d g i n g the degree o f opening w i t h the eye., supplemented w i t h o c c a s i o n a l micrometer r e a d i n g s . The number of stomata i n each group per hundred stomata was r e c o r d e d f o r each sample, and the average w i d t h of the stomata i n each sample was c a l c u l a t e d . Beans. The number of stomata per square mm. on upper and lower s u r f a c e s of the bean l e a v e s was c a l c u l a t e d u s i n g the c o l l o d i a n method,, A drop of c o l l o d i o n i s p l a c e d on the l e a f and a l l o w e d to form a t h i n f i l m . When t h i s hardens i t i s s t r i p p e d o f f and examined, For s t o m a t a l measurements the under s u r f a c e was used s i n c e t h e r e i s . a p p r o x i m a t e l y t e n times the number of stomata per square mm. on the lower s u r f a c e as on the upper s u r f a c e (Table 9 ) . Tlie l e a v e s c o u l d not be s t r i p p e d by making a p r e l i m i n a r y c u t because the leaves, a r e too t h i n . To o b t a i n a a t r i p a r i d g e on the under s u r f a c e -17-caused by s m a l l v e i n was grasped w i t h the f o r c e p s and then t o r n i n a d i r e c t i o n a t r i g h t angles t o the v e i n . I n t h i s way a p i e c e o f ep i d e r m i s was o b t a i n e d • w i t h very l i t t l e o t h e r t i s s u e connected t o i t . I t was immediately plunged i n t o a b s o l u t e a l c o h o l and s t a i n i n g was found t o be unnecessary. Leaf samples of d i f f e r e n t ages were taken from the t r e a t e d and c o n t r o l p l a n t s . Transverse measurements of the stomata were made w i t h a f i l a r micrometer. On one o c c a s i o n s u f f i c i e n t s u l p h u r d i o x i d e ' was g i v e n t o cause v i s i b l e l e s i o n s . The l e s i o n s f i r s t appeared as watersoaked a r e a s . Samples were t a k e n of the ep i d e r m i s from the watersoaked p a r t s and from the normal p a r t s of the same l e a v e s and samples were taken from c o n t r o l l e a v e s a t the same time. These l e a f samples were taken w i t h i n one h a l f hour of the time the i n j u r y occured. Comparisons were made of the degree of opening of the stomata i n a l l c a s es. Method of t r e a t i n g d a t a . T r a n s p i r a t i o n measurements. For each experiment t a b l e s have been made showing the amount of t r a n s p i r a t i o n i n grams per j a r per day d u r i n g the g r e a t e r p a r t of the p e r i o d of growth. T h i s d a t a has been i n c o r p -o r a t e d i n a graph i n c l u d i n g the c o n c e n t r a t i o n and d u r a t i o n of s u l p h u r d i o x i d e . A second t a b l e g i v e s the t r a n s p i r a t i o n of t r e a t -ed and c o n t r o l p l a n t s i n grams per hour per square metre d u r i n g the l a s t few days of the experiment. The leav e s were -18-measured on. the l a s t day of the experiment and i t i s assumed that very l i t t l e Increase i n l e a f area w i l l have occured In tlie three days preceding measurement, Stomatal measurements. In Experiment 2 a graph was made with the average transverse measurement of stomata p l o t t e d against the time In hours a f t e r the beginning of l i g h t or of darkness. In Experiments: 2, 3, and 4 the data i s given as percentage of stomata open, p a r t i a l l y or e n t i r e l y , and average width of open stomata. - 1 9 -DATA. F i r s t Experiment. P l a n t m a t e r i a l usedr D u c k b i l l barley. H i s t o r y of p l a n t s : Seeds set to germinate Nov. 1 7 . Seeds planted and j a r s sealed ................. H O Y . 1 9 . Jars placed I n plant chambers ................. Dec. 1 . Periods of sulphur dioxide treatment: Jan. 1 7 , 9:30 P.I. to Jan. 1 9 , 4:30 P.M. Concentration: average .2 parts per m i l l i o n . Jan. 2 5 , 6:00 P.M. to Jan. 2 9 , 1:00 P.M. Concentration: .41 to .57 p.p.m.. Jan, 2 9 , 5:30 P.M. to Jan. 3.1. 5 3 0 P.M. Concentration? .3 to .5 p.p.m.. Total treatments 1 8 2 hours. P l a n t s measured and discarded ....,.».........* Jan. 3 1 . Environmental c o n d i t i o n s : S o i l : R i c h loam s o i l . Water holding c a p a c i t y - 8 0 . 5 $ . S o i l moisture used - 4 0 $ of dry weight. L i g h t : Two 1 0 0 0 Watt lamps above each cabinet, 5-f f e e t , above the p l a n t s . 1 6 hours per day. -20-Temperature: 58*]?. to 91'F. Average d a i l y maximum - 77.5'F. Average d a i l y minimum - 65.0'F. - R e l a t i v e humidity: 31$ to 6.2$;. Average d a i l y maximum - 56.8$". Average d a i l y minimum - 42.0$. Appearance of p l a n t s a f t e r t r e a t m e n t : The leaves of treated p l a n t s were a s l i g h t l y l i g h t e r green than those of the c o n t r o l p l a n t s . A f t e r the treatment of .2 p.p.m. there was p r a c t i c a l l y no v i s i b l e i n j u r y to the p l a n t s . Following the treatment of .5 p.p.m I r r e g u l a r l y shaped areas bleached to a y e l l o w i s h white appeared on the leaves s t a r t i n g from the t i p s . The white merged i n t o brown on the edges of the areas, Second Experiment. Pla n t m a t e r i a l used: D u c k b i l l b a r l e y . H i s t o r y of p l a n t s : Seeds set to germinate * Jan. 31. Seeds planted and j a r s sealed Feb. 3. Shoots appeared above wax s e a l and j a r s placed i n p l a n t cabinets Feb. 5. A i r a t i o n h o l e s sealed over and j a r s brought to base weight Feb. 8• -21-Periods of sulphur dioxide treatment: Feb. 18 to Feb. 20, 21 hours, per day. Concentration: average .32 p.p.m.. Feb. 21 to Mar. 13, 21 hours per day. Concentration: average .22 p.p.m.. Mar. 18 to Mar. 23, 21 hours per day. Concentration: average .18 p.p.m.. Total treatment: 588 ho u r s . Samples of leaves of treated and co n t r o l plants taken on the f o l l o w i n g days: Mar, 9, 38 t h day, 12M., 2 P.M.. Mar. 10, 39th day, 12M., 2, 7, 8, 9, 10 P.M.. Mar. 11, 40th day, 8, 10, 11:30 A.M., 2, 5 P.M.. Mar. 19, 48th day, 3, 4:30 P.M.. Mar. 21, 50th day, 8:30, 10:30 P.M.. Mar. 22, 51st day, 9, 10:30, 11:3.0 A.M., 3, 5, 9:15P.M. Mar. 23, 52nd day, 10 A.M., 2. P.M.. P l a n t s measured and discarded: Mar. 23. Environmental c o n d i t i o n s : S o i l : As i n Experiment One. L i g h t r As i n Experiment One. Temperature:. 59 * F . to 92*F. Average d a i l y maximum - 77 , F , Average d a i l y minimum 68.7 *F. -22-R e l a t i v e h u m i d i t y : 23$ to 56$. Average d a i l y maximum - 47 .6$ . Average d a i l y minimum - 36 .8$ . Appearance of p l a n t s a f t e r t reatment : There was a s l i g h t browning of the t i p s of the leaves of both t r e a t e d and c o n t r o l p l a n t s . Some of the t i p of younger leaves became d r i e d out but n o t bleached d u r i n g the l a s t . t reatment . T h i r d E x p e r i m e n t . P l a n t m a t e r i a l u s e d : Dwarf beans, B r i t t l e W a x ' v a r i e t y . H i s t o r y of p l a n t s : Beans p l a n t e d and p l a c e d i n p l a n t c a b i n e t s J u l y 27 Jars s e a l e d w i t h wax. Aug . 8 P e r i o d s of s u l p h u r d i o x i d e t rea tment : A u g . 29 to S e p t . 2, s i x hours per day d u r i n g the l i g h t p e r i o d . \ C o n c e n t r a t i o n : average .11 p . p . m . , l i m i t s - .08 to ,17 p . p . m . S e p t . 14 t o S e p t . 16, s i x hours per day d u r i n g the l i g h t p e r i o d . C o n c e n t r a t i o n : average .2 p . p . m . , l i m i t s - .1 to .26 p . p . m . S e p t . 21 t o S e p t . 26, s i x hours per day d u r i n g the l i g h t p e r i o d . C o n c e n t r a t i o n : average .175 p . p . m . , l i m i t s - .10 to .21 p . p . m . -23-Leaf samples taken on the days of treatment. Plan t s measured and discarded ............... Sept. 26, Environmental conditions? • S o i l : As i n Experiment One. L i g h t : Pour 1000 Watt lamps per cabinet, 5-f- f t . above the p l a n t s . 11 to 12 hours per day. Temperature: 65 'F. to 95'F. Average d a i l y maximum - 88.4'F. Average d a i l y minimum - ?1.7;tF. R e l a t i v e humidity? 38$ to 73$. Average d a i l y maximum - 63$. Average d a i l y minimum - 46.7$. Appearance of plant s a f t e r treatment. There was no v i s i b l e i n j u r y to the p l a n t s . Both treated and c o n t r o l groups appeared to be s i m i l a r . Fourth Experiment. P l a n t m a t e r i a l used: Dwarf beans, Master piece v a r i e t y . H i s t o r y of p l a n t s . Beans planted, four per j a r .................. Jan. 1. The two best plants per j a r s e l e c t e d , the others removed and the surface of the j a r s waxed ..... Jan. 25. *~24-Periods of sulphur dioxide treatments Feb. 20, four hours during the l i g h t p e r iod. Concentration; average .11 p.p.m., l i m i t s - .09 to .14 p.p.m.. Feb. 23, four hours during the l i g h t p e r i o d . -Concentration: average .16 p.p.m., l i m i t s - o i l to .18 p.p.m.» Feb. 27 to Mar. 1, four hours per day during the l i g h t p e r i o d . Concentration: average .15 p.p.m., l i m i t s - .08 to .17 p.p.m.. Mar. 3 to Mar. 9, seven hours per day during the l i g h t p e r iod. Concentration: average .24 p.p.m., l i m i t s - .11 to .32 p.p.m.. Mar. 14 to Mar. 19, ten hours per day during the l i g h t p e r iod. Concentration:, average .17 p.p.m., l i m i t s - .12 to .19 p.p.m.. Total treatment 94 hours. Leaf samples taken on the days of treatment. P l a n t s measured and discarded Mar. 20. Environmental c o n d i t i o n s : S o i l : As i n Experiment One. L i g h t : Four 1000 Watt lamps above each cabinet, 5-f f t . above the p l a n t s . 12 t o 13 hours per day. Temperature: 58'P. t o 99' F. Average d a i l y maximum- 9 3 1 F . Average d a i l y minimum- 66'P. R e l a t i v e h u m i d i t y : 25$ t o 89$ Average d a i l y maximum- 64$ Average d a i l y minimum- 36.5$ Appearance of p l a n t s a f t e r t r e a t m e n t . Both t r e a t e d and c o n t r o l p l a n t s w e r e . s i m i l a r i n appearance u n t i l the treatment of Mar. 9 when c o n s i d e r a b l e i n j u r y occured. The c o n c e n t r a t i o n at the time of the i n j u r y r o s e t o ,32 p.p.m. which caused i n j u r y t o v i g o r o u s medium s i z e d l e a v e s of a good green c o l o u r . Tlie younger l e a v e s below 5 cm. i n l e n g t h and o l d e r leaves above a p p r o x i m a t e ^ 8 cm, i n l e n g t h were u n i n j u r e d . The l e a v e s most b a d l y a t t a c k e d w i l t e d from the base of the main p e t i o l e and soon d r i e d out c o m p l e t e l y . The i n j u r e d areas on other l e a v e s f i r s t appeared as watersoaked areas i n the r e g i o n s removed from the v e i n s . The r e g i o n s c l o s e to the v e i n s remained normal. The i n j u r e d areas d r i e d out c o m p l e t e l y i n a few hours l e a v i n g a dry l i g h t brown papery a r e a . A second i n j u r y of l e s s e x t e n t occured d u r i n g the treatment -of Mar. 17 when the c o n c e n t r a t i o n was 119 p.p.m., the temperature S3 1 P. and the r e l a t i v e h u m i d i t y 42$. -26-Table 1. T r a n s p i r a t i o n i n grams per day. F i r s t Experiment. Jar So. No. of No. of days of growth. Plants 26 -30 30-33 33-51 51-61 61-63 63-69 69-73 73-75 C 11. 3 8 .73 12.5 17.0 29.7 33.3 35.8 55.5 57.3 C 2. 3 10 .63 12.6 17.5 29.5 34.1 43.1 48.5 68.5 C 3. 2 6 .9 6.8 16.2 28.5 31.4 21.9 35.9 37.3 C 4. 3 10 .87 12.1 17.7 29 . 6 35.9 37.6 52.1 55.9 C 5. 3 8 . 55 4.5 12.4 26.8 27.3 28.1 40.6 32.65 C 6, 4 12 .8 13.5 19.0 31.1 30.45 38.1 51.5 60.25 C 7. 3 10 .3 11.6 17.9 28 .2 41.8 41.4 55.7 38.45 C 8« 3 8 .27 9.9 17 .2 28.9 30.3 36.2 48.7 49.7 C 9. 3 7 .87 8.6 17.7 31.2 30.3 39.4 ' 52.1 56.6 CIO. 5 10 .5 9.5 19.6 29.4 27.5 40.2 47.8 65.6 T o t a l 32 95 .42 101.6 172.2 292.9 322.35 361.8 488 .4 522.25 Average per j a r 9 .54 10.16 17.22 29.29 32.24 36.18 48.84 52.23 Average per plant 2 .98 3.17 5.38 9 .16 10.08 11.30 15.25 16 .33 T 1. 3 T 2. 5 T 3. 3 T 4. 4 T 5. 2 T 6. 3 T 7. 3 T 8, 5 T.9. 2 T o t a l 30 Average per j a r Average per pla n t 9.3 10.4 2 2.3_ 2 2 ft 0 11.5 11.9 14.8 9.6 5.2 6.7 11.5 13.1 14.0 13.6 21»*o 2 3 • 3 6.0 6.6 115.6 117.2 12.84 13.02 3.83 3.91 16.1 25.3 op o « L 19.0 32.0 17.9 28.5 11.8 27 .7 19.5 33.0 18.6 29.7 22.8 32.3 16.7 27 .7 165.2 259.3 18.35 28.8 5.51 8.64 - 3 PT 30.1 24.6 31.9 51.5 32.0 42.6 31.6 37.6 30.1 28.8 27.2 31.6 26.1 23.6 40.8 36.7 27.8 29.1 278.6 306.1 31.0 34.0 9.29 10.2 PT PT 34.7 27.5 49.6 34.6 48.8 24.2 43.9 27 .6 37.6 22.5 40.6 27.4 31.9 33.9 55.3 32.2 39.1 21.9 381.5 251.8 42.3 26 .1 12.71 8.4 C C o n t r o l p l a n t s . ^T Treated p l a n t s . 5PT.... Periods of treatment. -27-Table 2.. T r a n s p i r a t i o n In grams per clay. Second. Experiment. Jar No. of No. of days of g rowth. No. \ Plants 9-16 16-19 19-21 21-31 31-37 37 -.42 42-47 47-52 C 11, 4 9 .6 15.6 30.3 33.0 34.8 42.6 39.7 46.4 C 2. 5 6 .9 13.0 21.2 28,0 •'26.1 38.4 42.4 30.3 C 3. 5 7 .7 13.2 27 .5 31.1 40.1 41.2 41.5 40.1 C 4. 4 7 .9 14.6 47.2 28.3 33.1 37.9 44.8 26.8 .0.5. 5 7 .7 15.1 33.2 39.8 36.4 44.4 37.9 40.9 0 6. : 4 7 .8 14.8 26 .3 30.7 48.1 44.7 28.6 23.2 C 7. 4 9 .8 15.6 30.8 33.7 39.1 42.9 36.3 27.7 C 8. 3 -8 .6 16.4 28.5 30.2 26.8 44.1 30.7 28.8 C 9. 3 5 .9 12.9 20.8 29.6 29.6 .33.1 30.0 25.6 CIO. 6. 7 .4 15.3 23.4 26.0 33.5 47.8 48.5 45 .4 T o t a l 43 79 .3 133.6 268.4 310.4 347.6 417.1 380.4 335.2 Average per j a r 7 .9 13. 4 26-.S 31.0 34.8 41.7 38.0 33.5 1 Average per pla n t 1 .85 3.41 6.72 7.21 ••' 8.08 9.7 8.85 7.79 • fT ET FT PT T 2 1 . . 4: 12 .2 21.3 39.1 46,5 41.9 45.9 27.1 26.3 T 2. 4 12 .1 25.0 55.5 50.5 57.5 DO » *o 37.0 49.5 T 3. 4 •6 .8 12.4 20.3 28.8 34.9 34.6 . 37.1 .. 32.3 T 4, . 4 8 .0 20.1 .31.3 43.8 45.2 46.2 28.5 34.3 T 5,. 5 7 .9 16.9 29.5 35.7 38.1 40.2 37.8 •32 * 3 T 6. 5 8 .7 11.6 22.5 35.2 39.9 35.8 30.5 41.7 T.7. 4 9 .5 23.2 28.8 40.2 49.6 ' 52.1 31.8 ,3.9.4 T 8. 4 6 .5 16.4. 2 3 . 1 34.8 33.9 37.2 32.8 34.0 T 9 . - 4 8 .3 18.6 28.7 45.6 50.3 45.9 37. 9 < 46.9 TIO. 4 7 • 0". 16.6 3T.15 41.7 40.3 43.7 31.4 26.3 T o t a l 42 -.- 87 .0 182.1 289.9 402.8 431.6 436 .8 331.9 3,63.0 Average per j a r 8 .7 18 .2 2.9.0 40.3 43.2 43 .7 3.3.2 36.3 Average per p l a n t 2 .07 4.34 6.9 9.58 10.25 10v37 7.9 , 8.64 1C... . .Control p l a n t s . ZT...Treated p l a n t s . 3PT..Periods of treatment. ILoja_t.r„oJL T r e a t e d P e r i o d of) treatment w i t h c o n c e n t r a t i o n i n p a r t s N. B. Dayj of growth" i s mid-point betwejen beg inn i! J 2©?liod„Qj^ ipen mi 11 ion rig and end of •3 -28-Jar No. No. of Plants 14-17 1. 2. 3. 4. 5, 6. 7. To t a l Avera_ per j a r Average per plant T 2. 2 3 2 2 • 3 2 3 2 '3 22 3.. 4. 5. 6. 7. 8. 9. To t a l Average per j a r Average Per plant 17.6 31.5 23.8 12.9 28.5 21.8 30.8 20.6 21.8 209.3 23.2 -9.13 17-20 20.6 58.8 26.8 14.4 '35.4 25.2 30.6 '22.1 25.2, 37.5 54.2 53.0 29.1 69.3 42.7 41.7 31.6 27.8 259. T 386.9 29.7 43.C 11.78 17.6 2 20.1 23 . 6 22 .5 2 30.7 30 .7 45 3 28.3 32 .5 62 .6 3 25-. 5 30 .4 22 .8 3 30.2 34 2 39 7 2 35.2 36 1 67 9 2 26.1 30 9 35 2 3 27.4 25 9 22 1 3 28.9 32 1 35 7 23 252.4 276. 4. 353. 7 28.1 30. 7 39. 5 Table 3-. Transpiration In grams per day. T h i r d Experiment. No. of days of growth. 35-37 37-44 44-46 46-50 28-33 33- 35 13.6 32 .1 40.4 55 .6 36 .8 74 .3 22.9 45 ..4 38.5 76 .7 37.9 - 72 .9 25.0 51 7 21.6 57 1 17.8 30 3 254.5 496 1 28.3 55. 2 11.56 22. 5 16,0 31.3 38.9 18.9 27.6 26.8 20.1 17.9 20.8 24.; 10.9 12.03 15.53 12.2 44.0 34.9 73.4 15.1 2S.0 65.7 11.8 29.1 37.9 37.9 14.81 33.2 72 .5 • 102 .8 59.0 101.6 66.6 70.7 74.7 . 31.3 67.9 23.26 PT 64.6 40.6 93.7 25.9 40.6 84.4 25.2 44.4 34.4 453.8 50.2 19.7 lc Control plants. 'T. Treated plants. 3PT Periods of treatment. 33.3 71.7 83.0 60.6 97.8 74.1 70.5 77 .8 41.8 31.0 52.2 97.7 55.0 64.1 40.4 65.0 42.5 26.0 510.0 474.7 632 .0 67.8 52.8 70 .2 23.2 21.6 28 .7 73.7 45.1 74 r . 50.4 45.6 70 5 85-. 8 80.3 86 0 35.3 30.C 63 7 57.5 35.7 73. 0 87.9 4fe.5 75. 2 27.] 27.4 59. 0 52.8 37.5 67. 8 41.2 35.0 68. 5 50-52 52-55' 55'57 57-59 55.7 75.3 89.2 49.0 84.8 74.5 70.5 73.5 59.5 511.7 56.7 22.2 379.1 42.1 16.4 637.9 70.8 27.7 66.4 74.9 125.4 90.1 72.8 81 .8 92.4 95.2 56.2 84.1 32.5 PT 64 . 7 78.6 67.2 59.7 70.2 85.4 66.4 71.2 75.0 638.4 71.0 27.7 52.2 67.4 71.7 '73.4 70.4 70.7 ' 73. S 51.0 42.0 82.1 101 .7 102.0 54.7 ' 98.3 83.8 86.6 75.8 68.7 66.8 80.9 87.2 67.3 98.3 86,2 93.0 72.0 63.3 26.0 34. 72.3 47.7 47. C 41.0 -54.4 62.4 47.7 62.6 56.0 491.1 54.5 21.4 PT 84.0 59.2 56.4 66.5 84.5 62.8 74.2 67. ] 84.0 638.7 71.0 27.7 32.5 PT 82.5 6C .9 76.6 '6E .4 74.5 74.5 75.9 9C.1 8S.6 696 .0 77.4 3C.2 '59-61 -47.7 116.4 87.7 76. i 66.5 59.4 79.0 75.3 65.1 572.4 753.7 715.0 673.2 63.5 83 .'7 79.5 74 8 .30.6 PT 98.7 73.5 66.4 65.4 67.6 80. 9 79.8 78.6 68.4 680.3 75.6 29.6 Table 4. Jar No. of No. Plants 29- 32 32-34 G1 1. 2 26 .7 46.7 C 2. 2 20 .8 36.3 0 S. 2 26 .8 37.5 C 4. 2 17 .2 24.5 C 5. 2 20 .0 37; 4 C 6. 2 24.9 45.3 0 7. 1 18 .7 37.3 To t a l 13 155 1 265.0 Average per ja r 22 2 37.8 Average per plant 13 0 20.4 T 21. 2 35. 0 50.1 T 2. 2 21. 3 36.8 T 3. 2 22. 4 38.4 T 4. •2 19. 8 31.7 T 5. 2 22. 2 39.3 T 6. 2 31. 8 39.5 34- 36 36- 39 39-41 41- 43 43-45 45-46 39 . £ 41 .7 '58.5 60 .3 68.6 74.2 42 . 5 38 .6 48.6 54 .7 51.4 63.2 34 .8 39 .4 46.3 56 . 9 62.8 57.7 36 .5 33 .7 36.2 56 .4 54.7 64.4 34 .7 34 .0 48.9 56 .8 58.2 61.2 34 .1 43 .6 46.7 63 .1 55.3 91.6 28 .7 38 1 49.3 55 1 63.5 61.4 250 269 1 334.5 434 414.5 453 .7 35 7 38 g 48.1 61 7 58.3 64.7 19 2 20 7 25.7 33 4 31.9 34.9 46-47 47-48 111.2 85.3 85.6 81.2 90.6 105.9 98.4 89.2 82.3 89.7 74.8 98.3 87.4 80.6 657.2 613.; 93.7 87.! 50.5 47.; Tr a n s p i r a t i o n In crams per day. Fourth Experiment. , No. of days of growth. 48-50 50-51 51-52 52-54 54-55 55-57 57-74.5 68.7 74.3 82.3 • 69.0 88.8 70.7 96.2 119.4 101.0 100.6 91.0 98.4 76.f 78.2 66.3 93.6 105.9 71.2 74.4 85.3 95.6 86.8 91.4 10].5 100^6 98.6 86.1 92.1 4t ll'.b 62.7 79. C 78.1 58-59 68.5 106.8 116.3 96.2 97.1 95.0 58. 94. 59. -62 62-64 64- 65-66 66-68 51 .8 99.4 64.7 95.8 89.6 53 .2 95.1 62 .6 98.7 105.8 97.9 124.1 119.6 97.2 52.4 97.6 64.2 103.6 109.8 528.3 Sc5.6 663.5 632.7 520.0 566.0 612.9 652.1 75.5 90.7 94.5 90.5 74.3 80.7 87.5 93.2 74.3 113.0 96 84.6 87.4 99 44.1 49.3 43 88.0 104.2 10£ 47.6 57.3 67 79.1 76.7 9] 73.8 97.2 95 68-69 69-71 71-73 73-74 74-76 76- 7 8 83.9 76.2 57.5 78.4 78.4 91.7 39.3 27.8 46.2 89. £ 76.1 90.1 49.7 34.2 61.2 69.1 77.7 67.8 83.4 65.9 85.0 62.7 48.1 49.5 76.4 39.6 56.3 72.4 58.2 56.1 48.3 71.8 43.7 55.4 56.1 70.4 41.2 48.9 87.6 42.2 54.3 74.9 60. 41, 50.4 40.7 49.0 51.0 48.7 40.C 43.5 47.2 50.1 644.9 491.5 585.6 596.6 493.0 92.0 70.2 83,5 85.1 70.5 49.G 37.8 45.0 45,8 37.9 436.3 519.5 405.0 339.6 419.5 318.6 5.5 39.9 51.5 60.1 58.3 78.3 41.1 43.8 66.3 68.7 74.2 97. 47.2 41.7 90.1 44.9 43.6 64.2 65.6 12 To t a l Average per j a r Average per plant JC Control *T Treated 3PT Periods 106.1 75.1 117.8 114 56.4 64.8 78.4 73 62.5 74.1 98.£ 104 68.2 74.7 112.3 78. 152.5 235.8 258.7 249.6 360.4 387.1 399.5 458.2 626.5 598 25.4 39.2 43.1 41.6 60.1 64.5 66.5 76.3 104.3 99, 12.7 19.7 2i.6 20.8 30.1 32.2 33.3 -38.2 52.2 49. plants. plants. of treatment. PT 3 .8 100.3 75.7 .9 92.8 .8 123.7 2 87. £ 0 94.8 0 573.5 7 95.5 8 47.8 114.4 84.2 134.7 89.2 93.7 88.1 604.3 ICC. 7 50.3 121 .4 98.3 67.7 64.2 113.1 100.9 94.2 47.1 PT 125.1 111 .3 119.8 85.9 116.4 ]14.7 673.2 112.1 56.1 .6 1C2.7 .0 103.8 .4 106.9 .0 95.6 .2 107.3 . 5 87 . 2 .7 603.5 .9 ICO.3 .9 50.2 PT 104.8 95.3 113.6 104.7 86.8 97.7 PT 108.4 103 93.2 100 158.7 104 108.1 116.0 121 .2 102. 98. 84. 72.3 80.4 64.7 92.1 73.3 68.9 97.2 88.1 104.8 99.7 105.4 86.0 FT 95.5 91.4 113.6 97.1 95.3 1C1 .S FT 75.4 74.2 104.1 79.8 76. 7 76.1 48.0 28.3 54.7 52.2 51.1 46. 7 59.4 54.3 63.6 70. £ 62.6 602.9 705.6 592 100.2 117.6 9G.C 76.1 50.1 58.7 49. s j.g.c 456.7 581.2 594.8 486. 96.8 48.4 81.0 40.5 57.8 55.6 59.9 45.5 31.1 30.0 32.3 24.5 PT PT PT PT 43.6 36.2 40.9 34.4 56.4 59.1 63.2 50.6 55.7 52.4 45.1 31.S 64.2 69.8 71.6 60.7 61.6 68.0 72.3 50.8 50.0 56.9 60.2 41.1 331.5 344.4 353.5 268.8 55.1 57.3 58.8 44.8 27.6 26.7 29.4 22.4 . I __Figure _8 . T r a n s p i r a t i o n i n grams per pl a n t per day! [. T h i r d Experiment. Nb. of days' of growth. :~r~ T r a n s p i r a t i o n i n grams per plant per day. ...... • ..j .. ... Fourth Experiment,, Period ofj treatment) with concentration).In parts (per m i l l i o n N . B D a y of. growth i s mid-point between beginning and end jof Table 5. Plant area and rate of t r a n s p i r a t i o n f o r f i n a l period of measurement. F i r s t Experiment. Jar No. of No. of No. pf Stem Leaf T o t a l Tran- Transpire No. - Plants Stems Leaves Area Area Plant s p i r a t i o n a t i o n i n - . Area f i n a l gm./hr./m , _ • p period of of plant cm. cm. cm. 51 hours, surface. C1 1. 3 8 19 209 256 721 114.6 gm. 29.8 C 2. 7 25 163 287. 738 137.0 39.9 C 3. 2 5 15 171 234 640 74.6 22.85 C 4. 3 8 22 162 387 935 111.8 23.4 G 5. 3 7 20 185 343 870 65.3 14.74 C 6. 4 7 24 174 419 1012 120.5 12.22 C 7. 3 6 17 117 253 623 76.9 24.25 C 8. 3 9 21 191 308 807 99.4 24.1 C 9. 3 8 27 152 419 990 113.2 22.46 CIO. 5 10 31 . 183 416 1015 131.2 25.7 T o t a l 32' 75 221 1707 3322 8351 1044.5 gm. 239.42 Aver a ge pen j a r 7.5 22.1 171 332 835 104.5 gm. 23.94 TZ 1. •7 6 14 124 211 546 55.0 •gm. 19.8 T 2. 5 10 23 192: 295 782 69.3 17.4 T 3. 3 7 20 169 301 771 48.5 12.32 T 4. 4 7 27 142 318 775 55.1 13.94 T 5i .2 : 7 19 153 237 627 45.1 14.1 T 6. 3 7 14 206 221 647 54.8 16.63 T 7. 3 10 • 24 187 273 733 67.9 18.15 T 8. 5 8 22 148 282 712 64.4 19.57 T 9. 2 8 16 ; 146 182 . 510 43.7 gm. 16.83 T o t a l 30 70 179 1467 2320 . 6103 503.8 gm. 148.74 Average per j a r 7.8 19.9 163 258 678 56.0 16.53 C .... .Control plants.. 2T.....Treated p l a n t s . ^Leaf area,"one side only. . . . 4T o t a i plant area includes area of stems and both sides of leaves. -31-. Table 6. Plant area and. rate of t r a n s p i r a t i o n f o r f i n a l period of measurement. Second Experiment. Jar N'o. Of No. of No. of Fresh Stem Le a f 3 T o t a l 4 T r a n s p i r -No. Plants Stems Leaves Weight Area Area P l a n t a t i o n : , Area f i n a l period of gm. sq. cm. sq. cm. sq. cm. 120 hours. C 1!. ..4 6 20 16.8 149.8 419. C 987.8 231.8 gm. C 2. 5 • : 9 23 1.4.3 144.3 371.0 886,3 151.5 C 3. 5 6 21 16 .0 134.6 392.5 919.6 200.7 C 4. 4 '•: 7 18 11.8 111.6 283.5 678.6 133.8 C 5. 5 10 24 17.2 . 173.4 433.0 1039.4 204.5 C 6-. ' . 4 9 21 13.3 131.2 324.0 779.2 116 .1 C 7. .  . 4 . 9 ' 20 14.1 142.2 333 .0 808.2. 138.5 •C 8. 3 7 18 13.2 : •113 .6 350.7 815.0 143.8 C 9.. 3 6 15 11.6 . 114.6 514.0 742 .6 127.9 c i o . ; 6 9 • 26 19 .6 193 .0 546.0 1285.0 227.1 T o t a l 43 78 206 147.9 1408.3 3766 .7 8941.7 1675.7 gm. Ave.ra ge per j a r 7.8 20.6 14.8 140.8 376.7, 894.2 .167.6 gm. T 21. ••' 4 11 23 12.7 153.6: 283.0 719.6 131.4 gm. T 2. 4 10 27 17.6 212.1 401.5 1015.1 247.6 T 3. 4 12 28 15.1 175.6 596 .5 968.-6. 161.3 T 4. . 4 9 18 15.2 194.3 312.0 818.3 171.4 T. 5. . 5 ' 11 28 - 16.4 178.3 376.0 930.3 161.5 • T 6. 5 7 21 14.8 147.7 347.0 841.7 208.5 T 7 . 4 : 10 ' 24 14.6 157.. 4 . 361.5 880.4 - •' 197.1 T 8. 4 5 12 14.9 187 .7 245.0 677.7 170.2, T 9. 4 . 7, 24 15.9 168.9 407.0 982.9 .234.3 TIO. . •4 10 20 13.6 159.6 284.0 727.6 131,7 gm.; T o t a l 42 92 225 150.8 1735.2 3413.5 8562.2 18.15.0 gml Avera ge per jar • !: 9.2 22.5 15.1 173.5 341.4 856 o 2 181.5 gm. Tra n s p i r -a t i o n i n gm./hr./sq. metre of plant surface. 19.33 14.25 18.25 16.93 16.40 17.22 14.30 14.70 17.23 14.72 163.33 16.33 15.2.0 20.30 13.89 17 .45 14.47 20.70 18.68 20.90 19.85 15.10 .176 .54 17.65 1 C . . . . . C o n t r o l p l a n t s . *T.....Treated p l a n t s . 3 Leaf area,.one side only. 4 T o t a l plant area Includes area of stems and both sides of leaves. Table 7. Leaf area and rate of t r a n s p i r a t i o n f o r f i n a l period of measurement. T h i r d Experiment.. No. of Leaf A r e a 3 T r a n s p i r a t i o n T r a n s p i r a t i o n Plants i n sq. cm. i n gm. : f i n a l i n gm. per hr. period of 48 per sq. metre hours. of l e a f surface. C 1!. 2 1774.1 95.4 11.20 C 2. ; , 3 2380.9 232,8 20.64 C 3. 2 2293.0 175.4 15.96 C 4. 2 • 1873.0 152.2 16.94 C 5. 3 2010.0 . 133 .0 13.70 C 6. 2 1931.0 118.7 12.80 C 7. 3 2040.5 .158.0 16.69 C 8. •" 2 2513.3 .150.6 12.28 C 9.. 3 1646.0 130.1 16.47 T o t a l . 22 18,461.8 1346.2 136.68 Average per j a r 2051.3 149.6 15.18 T 21. 2 1933.5 197.3 21.25 T 2. 2 1784.0 147.0 17.17 •T .3. 3 1644.4 132.9 •16.83 T 4. 3 1427.0 130.8 20.20 T 5. \ 3 2047.8 135.2 13 .73 T 6. 2 172*9.0 161.9 19.59 T 7. 2 . 1327.0 159.5 25.00 T 8. 3 1551.0 .159.2 21.35 T 9. 3 2041.1 136.8 13.95 T o t a l 23 15,484.8 1360.6 168.98 Average per j a r 1720.5 151.1 18.77 1 C . . . . . C o n t r o l p l a n t s . ....Treated p l a n t s . 3 L e a f area, one s i d e . Table 8, Jar No. C 1. C 2. C 3. •C 4. C 5. C 6"^  G 7. •No. of Pla n t s 2 2 2 2 2 2 1 T o t a l 13 Average per j a r T 1. T 2. T 3. 4. 5, 2 2 2 2 2 2 T o t a l 12 Average per j a r Leaf area and rate of t r a n s p i r a t i o n during f o u r l a s t periods of measurement Fourth Experiment. 71st-73rd dav No. of Leaf Leaves Area p cm. Tran-s p i r -a t i o n gm/hr. Rate ^per uh i t l e a f area 66 50 61 60 52 50 56 395 1526.0 1562.7 897.5 1595.0 872.9 900.5 1552.6 2.62 ' 17.2 2.00 12.3 2.06 22.9 3.19 20.0 1.605 18.4 2.71 30.0 3.00 19.3 8907.2 17.18 140.1 56.4 1272.4 2.45 20.0 44 63 44 73 76 76 376 851.0 880.9 611.7 953.3 1500.1 1358.2 1.81 2.71. 2 • 3 2 2.67 2.58 2 .08 21.3 30.8 38.0 28.0 17.2 15.3 6255.2 14.17 150.6 62.7 1042.5 2.36 25,. 1 73rd-to74th day No. of Leaves 47 47 60 58 49 48 52 361 Leaf Tran-Area s p i r -at i on cm. gm/hr 1033.6 1483.2 859.7 1511.3 842.7 840.1 1352.6 2.42 2.33 2.00 3 .00 1.83 2.29 2.33 Rate per u n i t l e a f area 23 .4 15.7 23.2 19.85 21.7 27.3 17.2 7923.2 16.20 148.35 51.6 1131.9 2.31 21.19 42 61 44 73 73 76 369 797.5 843.0 611.7 953 .3 1368.0 135.8.2 1.50 2.46 2.17 2»02 2.83 2.46 18.8 27.9 35.5 30.7 20.7 18.1 5931.7 14.34 151.7 61.5 988.6 2.39 25.3 74th-76th day No. of Leaf Trans-Leaves Area spir'-Rate" per u n i t l e a f area 37.4 13.1 29.4 25.1 23.0 27.4 23.0 46.9 1024.8 2.49 25.5 O a t i o n cm. d gm/hr 39 782 .1 2.92 42 1307 .9 1.71 50 694 .4 2.04 56 1455 .3 3.66 43 760 .0 1.75 46 821 .4 2.25 52 1352 .6 3.12 328 7173 .7 17.45 39 61 43 73 70 76 362 706.7 843.0 601.6 953.3 133 5.0 1358.2 1.71 22.5 2.61 31.1 1.875 31.2 3.00 31.5 3.00 22.5 2.50 18.4 4697.2 14.69 157.2 60.3 782 2.45 26.2 76th-78th day No. of Leaf Tran Leaves Area spin-cm^ Rate per at i o n u n i t l e a f area gm/hr 32 616.9 2.69 43.70 38 1174.2 1.39 11.85 42 546.9 1.36 24.90 52 1327.7 2.92 22.20 40 - 690.1 .805 11.67 46 821,4 1.735 21.20 52 1352.6 1.89 14.00 302 6579.8 12.79 149.52 43.1 940.0 1.83 21.36 39 706.7 . 1.69 23.90 47 481.9: 1.29 27.30 38 554.6 1.76 31.80 48 275.1 1.375 50.00. 53 1012.7 2.53 25.00 53 776.9 2.18 28. 10 278 3807.9 10.82 186.10 46.3 634.6 1.67 31.01 1 C . . . . . C o n t r o l p l a n t s . ZT.....Treated p l a n t s . 3 Rate of t r a n s p i r a t i o n i n grams per hour per square metre of l e a f surface, one side only. -34-Table 9. Number of stomata per square mm. D u c k b i l l b a r l e y Leaf sheaths 32 Leaves Upper surface 32.9 Lower surface 28.8 B r i t t l e Wax beans leaves Upper surface 43 Lower s u r f a c e 395 Masterpiece beans Leaves Upper s u r f a c e 40.8 Lower s u r f a c e 335 P l a n t Table 10. Transverse measurements of stomata. Average w i d t h of stomata i n m i c r o n s . B a r l e y Medium aged leaves B r i t t l e Wax beans Medium aged leaves Masterpiece beans Young leaves Medium aged leaves Old Leaves C o n t r o l 1.5 l u . 3 . 29u . 3 .48u. . 3 . 97u . 2.6 2u. T r e a t e d u n i n jured 1.6 l u . 2 .46u. 3 .75u. 3 ,49u . 2 .28u. Treated i n j u r e d 3 .86u. 4 .08u. 2 .02u. „ ... F igui -e 11. taken jlverage width of stomata per a f t e r var ious periods of l i g h Second Experiment . Leaf sampl b and of d 3 arkness . D u c k b i l " L b a r l e y . CQ o 2u 0 •— • • •• : % • '• X o < • H 3 l u ' o X 0 X t X X o X o o X x * X o oo X < X ° < x * o x X > * o < « 1 ) ferage wid 0 < 8 6 4 2 0 2 Hours of d a r k n e s s . fc 6 ft 10 IE ^ 4 ] J 6 Hours of l i g h t . C o n t r o l T r e a t e d V a r i a t i o i i i n width of stomata i s as creat f o r c o n t r o l 1 .eaves as ; for t r e a t e d l e a v e s . E i i . 1 -35-Table 11. Percentage Of stomata open. Plant Control Treated Treated uninjured i n j u r e d Barley Medium aged leaves 73.5$ 71.5/ B r i t t l e Wax beans Medium aged leaves 62.7/ 51.3/ Masterpiece beans Young leaves 64.2/ 62.6^ 61.4/ Medium aged leaves 62.4/ 67.3/ 6 5.4/ Old leaves 51.8/ 47.2/ 48.5/ -36-. " '• DISCUSSION-OP RESULTS In comparing.the average t r a n s p i r a t i o n per plant i n grams per day f o r each of the two groups i n each experi-ment there i s considerable v a r i a t i o n i n r e s u l t s . In Exper-iment 1 the two groups are f a i r l y equal u n t i l a f t e r a t r e a t -ment of .5 p.p.m. which caused i n j u r y , whereupon the t r a n s p i r a t i o n from, t r e a t e d plants immediately dropped (Table 1 and P i g . 6) due, probably, to the reduction i n f u n c t i o n a l l e a f area by i n j u r y . In Experiment 2 (Table 2 and F i g . 7) there i s found to be no s i g n i f i c a n t d i f f e r e n c e between the two groups i f the d i f f erences between' t h e i r average values f o r the t r a n s p i r a t i o n per plant per day are test e d by a c a l c u l a t i o n of the standard d e v i a t i o n from the mean. A d i f f e r e n c e of twice the standard d e v i a t i o n from the a r i t h -metic mean i s considered to be s i g n i f i c a n t (3(). Both groups show a general trend of increase i n t r a n s p i r a t i o n to the 40th day a f t e r which there i s a decrease. Presumably the same1 f a c t o r s are operative i n both cases and the reduction i s probably due to Increasing age. In Experiments 3 and 4 (Tables 3 and 4 and F i g . 8 and 9) the t r a n s p i r a t i o n of both t r e a t e d and c o n t r o l plants shows a general trend of increase up to the period between the 50th and 60th days of growth at which point Experiment 3 was discontinued and Experiment 4 which continued to the. 78th day shows a gradual reduction i n the amount of t r a n s p i r a t i o n . The- rather deep depressions -37 - . i n the graphs ( P i g . 8 and 9} occured on c e r t a i n occasions, when the l i g h t s were reduced i n number. With lower temper-ature rand higher humidity there was a r e s u l t a n t decrease i n transpiration,, This shows that there Is a more s i g n i f i c a n t [ p o s i t i v e c o r e l a t i o n between the two groups i n t h e i r r e a c t i o n to the environmental f a c t o r s of temperature and r e l a t i v e humidity than there i s a negative c o r e l a t i o n between the c o n t r o l and trea t e d plants„ In Experiment 3 (Table 3 and F i g * 8) the general average shows greater t r a n s p i r a t i o n from the c o n t r o l p l a n t s than from treated p l a n t s , however the two curves come together a t the f i n a l determination and the average r a t e of t r a n s p i r a t i o n per u n i t area as deter-mined f o r the f i n a l p eriod, i s a c t u a l l y higher f o r treated than f o r c o n t r o l as shown i n Table 3, Owing to the greater l e a f area of the c o n t r o l p l a n t s the t r a n s p i r a t i o n from approximately the 45th to the 62nd days can be considered to be p r a c t i c a l l y the same* The f a c t o r of area i s consid-ered more f u l l y below. Previous to that period the rate may have been l e s s from treated than from c o n t r o l p l a n t s * but the data i s not c o n c l u s i v e * In Experiment 4 (Table 4 and F i g , 9) the p a r a l l e l between the two graphs i s again very marked showing the e f f e c t s of varying temperature* I n j u r y occurred during t h i s experiment at a concentration of .32 p.pan., and eight days l a t e r at .19 p*p,m. showing that beans are extremely s e n s i t i v e to sulphur d i o x i d e , A comparison of the. r a t e of t r a n s p i r a t i o n f o r the f i n a l period of three days i n grams per hour per square metre of l e a f area "between the c o n t r o l and treated plants shows i n Experiment 1 (Table 5) s i g n i f i c a n t l y less t r a n -s p i r a t i o n from the t r e a t e d plants than, from the c o n t r o l s . The; reduction i n l e a f area due to i n j u r y would account f o r the reduced t r a n s p i r a t i o n . In Experiments 2 and 3 (Tables 6 and 7) there i s a s l i g h t d i f f e r e n c e i n the average rate f o r the two groups, but i n Experiment 2 the d i f f e r e n c e i s l e s s than the standard d e v i a t i o n from the mean of the two groups, and i n Experiment 3 the d i f f e r e n c e i s less than twice the standard d e v i a t i o n from the means of the two groups. In Experiment 4 (Table 8) the rate was c a l c u l a t e d f o r four periods of one to two days each near the end of the experiment. Here again the d i f f e r e n c e between the averages f o r the two groups i s l e s s than the standard d e v i a t i o n from the mean of each group. There i s a tendency i n both groups to increase the rate of t r a n s p i r a t i o n s l i g h t l y d u r i n g the f i r s t three periods, whereas i n the f i n a l p e r i o d measured, the t r a n s p i r a t i o n from the c o n t r o l p l a n t s decreases appreciably and that from the t r e a t e d plants increases^ as shown i n the graph, F i g . 10. A- study of the hygrothermograph records of t h i s l a s t p e r i o d show that the l i g h t was reduced f o r a few hours on one day and that the minimum and maximum temperatures f o r t h i s period are lower than u s u a l . These circumstances account f o r the decrease i n rate of t r a n s p i r a t i o n -39-f o r the- c o n t r o l p l a n t s . The i n c r e a s e d r a t e of t r a n s p i r a t i o n from the t r e a t e d p l a n t s may be a secondary e f f e c t of the i n j u r y w h i c h o c c u r r e d p r e c e d i n g the p e r i o d under d i s c u s s i o n . B a d l y i n j u r e d l e a v e s were removed so t h a t the r a t e c o u l d be c a l c u l a t e d on a b a s i s of f u n c t i o n a l l e a f area* A compar-i s o n o f the number of l e a v e s removed immediately p r e c e d i n g t h i s p e r i o d w i t h 'the i n c r e a s e i n r a t e o f t r a n s p i r a t i o n d u r i n g the p e r i o d shows r o u g h l y t h a t the g r e a t e r the number of l e a v e s removed the g r e a t e r the i n c r e a s e i n t r a n s p i r a t i o n , , as shown i n the f o l l o w i n g t a b l e ; f o , o f J a r H T o 0 o f l e a v e s Change i n t r a n s p i r a t i o n 'removed* . compared w i t h p r e c e d i n g p e r i o d , 25 0 3 0 14 36 5 37 25 38 17 42 23 + 114 " 3" & Q + =6 + '18»5 + a, 5 -f- 9,7 I t I s p o s s i b l e t h a t the removal of the i n j u r e d l e a v e s caused i n c r e a s e d l o s s of water a t the p o i n t s where they were removed from the stem. The r e s u l t s from the measurements of stomata show the same l a c k o f any s i g n i f i c a n t d i f f e r e n c e between t r e a t e d p l a n t s not showing v i s i b l e i n j u r y and c o n t r o l p l a n t s * I n Experiment 2. ( E i g , 11} the measurements from i n d i v i d u a l l e a v e s show g r e a t v a r i a t i o n s w i t h i n the c o n t r o l group and w i t h i n the t r e a t e d group. When each group i s averaged they show no s i g n i f i c a n t d i f f e r e n c e (Table 10}„ Experiment 3 -40-(Table 10); on the other hand, shows a wider average storaatal aperture f o r c o n t r o l plants than f o r t r e a t e d plants, and the d i f f e r e n t determinations are quite c o n s i s t e n t . This i s the. only case where there i s a s i g n i f i c a n t d i f f e r e n c e . In Experiment 4 there i s no s i g n i f i c a n t d i f f e r e n c e between the stomatal apertures of the c o n t r o l leaves, of uninjured areas of t r e a t e d leaves and of i n j u r e d areas of treated leaves, but there i s a d i s t i n c t d i f f e r e n c e i n stomatal aperture and percent of stomata open between yoimg, medium aged and old leaves, (Table 10), the medium aged leaves having the widest stomatal aperture, the young leaves s l i g h t l y narrower and the o l d leaves having a very harrow aperture. These r e s u l t s agree with the observation that medium aged leaves are most s u s c e p t i b l e to sulphur dioxide. Mien s t r i p p e d from the l e a f and examined under the microscope there was no n o t i c e a b l e d i f f e r e n c e i n appearance of the epidermis of i n j u r e d areas compared with mninjured areas. I t i s p o s s i b l e that the sulphu d i o x i d e a f f e c t s the mesophyll c e l l s f i r s t , by going i n t o s o l u t i o n In the moist walls then penetrates and k i l l s the c e l l s making them.freely permeable and thus causing the watersoaked areas. The drying out of these dead areas would produce the t h i n papery patches which are the f i n a l form of the i n j u r y . -41-C01TCLTJSI0E3. The c o n c e n t r a t i o n s a t which- i n j u r y -occurred show-t h a t beans are more s u s c e p t i b l e to the i n j u r i o u s e f f e c t of su l p h u r d i o x i d e than barley» When i n j u r y occurs- medium a ged leaves are most s u s c e p t i b l e and young and o l d l e a v e s are more r e s i s t a n t * Sulphur- d i o x i d e i n concentrations- w h i c h d i d cause i n j u r y reduced the t r a n s p i r a t i o n from, t r e a t e d p l a n t s by ' r e d u c i n g the f u n c t i o n a l l e a f a r e a , There was no evidence o f pronounced e f f e c t on the t r a n s p i r a t i o n of plants- t r e a t e d w i t h ' sulphur d i o x i d e a t c o n c e n t r a t i o n s which d i d not cause injury» There was no evidence of a s i g n i f i c a n t d i f f e r e n c e between the degree o f opening o f stomata o f c o n t r o l p l a n t s and t r e a t e d p l a n t s • This was t r u e o f stomata from areas which had been in j u r e d . , The s u g g e s t i o n i s made th a t the sul p h u r d i o x i d e a f f e c t s the meaophyll c e l l s f i r s t , when c a u s i n g injury„ . A l t h o u g h n e g a t i v e r e s u l t s cannot be cons i d e r e d to be c o n c l u s i v e the evidence from the f o r e g o i n g experiments I n d i c a t e s t h a t s u l p h u r d i o x i d e i n the c o n c e n t r a t i o n s used w h i c h d i d not cause i n j u r y * under the c o n d i t i o n s of l i g h t r temperature and r e l a t i v e h u m i d i t y w h i c h p r e v a i l e d a t the time does not cause a marked e f f e c t on the t r a n s p i r a t i o n or -42-s t o m a t a l openings* The c l o s u r e o f stomata r e c o r d e d i n Experiment 5 i s an e x c e p t i o n which i s not c o n f i r n e d "by the other results-» The evidence from-'.these experiments.,,- a l t h o u g h i n d e c i s i v e * i s a g a i n s t the t h e o r y that' sulphur d i o x i d e causes I n v i s i b l e i n j u r y i n c o n c e n t r a t i o n s below those which cause v i s i b l e i n j u r y * / ' SUMMARY. Four Experiments were c o n d u c t e d , two. on "barley p l a n t s and two. o n bean plants,, h a l f of the plants being t r e a t e d w i t h sulphur dioxide, and h a l f used as c o n t r o l s . Records were made of the t r a n s p i r a t i o n from the plants? and c a l c u l a t i o n s were made of the f i n a l r a t e of t r a n s p i r a t -i o n per u n i t of l e a f area. Measurements of stomata were made i n the two groups and- comparisons 'drawn. The r e s u l t s showed no s i g n i f i c a n t increase or decrease i n the amount of t r a n s p i r a t i o n i n e i t h e r b a r l e y or beans due to the e f f e c t of sulphur dioxide when used i n concentrations which d i d not cause Injury«, Where the sulphur dioxide caused i n j u r y the t r a n s p i r a t i o n was reduced. There was i n two experiments, no s i g n i f i c a n t d i f f e r e n c e between the- openings of stomata of the two groups» In one experiment there was a s l i g h t but d e f i n i t e r e d u c t i o n i n the s i z e . o f the s t o m a t a l aperture i n the treated, p l a n t s » I t has been concluded that the data give no support to the " I n v i s i b l e i n j u r y " theory of sulphur dioxide e f f e c t . ' -44-.BIBLIOGRAPHY 1. Briggs, L. J . , and Schantz, H. L. A wax seal method f o r determining the lower l i m i t of a v a i l a b l e s o i l moisture, Bot. Gaz. 51:210-219.. 1911. 2. Davis j "A. R., and Hoagland, D. R. An apparatus f o r the growth of plants i n a c o n t r o l l e d environment. Plant Physiology 3:277-292. 1928. 3. F i s h e r , R. A. S t a t i s t i c a l methods f o r research workers. O l i v e r and Boyd, Edinburgh. 1932. 4. Graf-Marin, A. Studies on powdery mildew of c e r e a l s . C o r n e l l U. A g r i c . Exp. Sta. Memoir 157. 1934. 5. G r i f f e n , S. W. , and Skinner, W.'W.' ..Small amounts of sulphur dioxide i n the atmosphere. I. Improved method f o r determination of sulphur dioxide when present i n low concentrations i n a i r . Ind. and Eng. Chem. 24 1932. 6 . •Holmes', J . A., F r a n k l i n , E. C., and Gould, R. A. Report of the Selby Smelter Commission. U. S. Dept. of the I n t e r i o r , Bureau of.Mines. B u l l . 98. 1915. 7. Jack, W. R. The absorption of inorganic n u t r i e n t s by plants t r e a t e d with sulphur d i o x i d e . Unpublished t h e s i s . U n i v e r s i t y of B. C. 1937. 8. Kiesselbach, T. A. T r a n s p i r a t i o n as a f a c t o r i n crop production. B u l l . A g r i c . Exp. Sta. Nebraska. No.. 6. 1916. -45--9. Lloyd, F. E. The-physiology.'of stomata. Carnegie Inst. Wash. Pub. 82. 1908. 10. L o f t f i e l d , J . V. G. The behavior of stomata. Carnegie Ins t . Wash. Pub. 314. 1921. .11. Maximov und Krasnosselsky-Maximov. F l u c t u a t i o n s i n the course of photosynthesis. Ben. Deutsch. Bot. Ges. 46: 383-391. 1928. ( B i o l . Abstracts 4: No. 619. 1930.) 12. Scarth, G.. W. Mechanism of the a c t i o n of l i g h t and other f a c t o r s on stomatal movement. Plant Physiology 7:481-504. 1932. 13. Setterstrom, C., Zimmerman, P. W., and Crocker, Wm. E f f e c t of low concentrations of sulphur dioxide on y i e l d of a l f a l f a and C r u c i f e r a e . Contr. Boyce Thompson I n s t . 9:179-198. 1938. 14. .Swain, R.E., and Johnson, A. B-. E f f e c t of sulphur dioxide on wheat development. Ac t i o n at low concentrations. Ind. and Eng. Chem. 28:42-47, 1936.. 15. Thomas, M..-D..,. and H i l l , G. R. R e l a t i o n of sulphur dioxide i n the atmosphere to photosynthesis and r e s p i r a t i o n of a l f a l f a . Plant Phys. 12:309.-383. 1937, 16. Wieler, A. Uber die Einwirkung von Sauren auf die Assim-i l a t i o n der Holzgewachse. Jahrb. Wiss. Bot. 78:483-543. 1933. ( B i o l . Abstracts 8: No. 15234. 1934.) 17. Zimmerman, P. W., and Crocker, Wm. T o x i c i t y of a i r c o n t a i n i n g sulphur dioxide gas. Contr. Boyce Thompson I n s t . 6:455-470. 1934. 

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