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Air Pollution Effects on Plant Growth
 9780841202238, 9780841201699, 0-8412-0223-0

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Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.fw001

Air Pollution Effects on Plant Growth

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.fw001

Air Pollution Effects on Plant Growth

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.fw001

M a c k Dugger, Editor

A symposium sponsored by the Division of Agricultural and Food Chemistry at the 167th Meeting of the American Chemical Society, Los Angeles, Calif., April 1,

1974.

ACS SYMPOSIUM SERIES

AMERICAN

CHEMICAL

WASHINGTON, D. C. 1974

SOCIETY

3

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.fw001

Library of Congress

Data

Air pollution effects on plant growth. (ACS symposium series; 3) Includes bibliographical references and index. 1. Plants, Effect of air pollution on—Congresses. I. Dugger, Mack, 1919- ed. II. American Chemical Society. Division of Agricultural and Food Chemistry. III. Series: American Chemical Society. ACS symposium series; 3. [ D N L M : 1. Air pollution—Congresses. 2. Plant diseases—Congresses. SB745 A298 1974] QK751.A37 ISBN 0-8412-0223-0

582'.05'222 74-26543 ACSMC8 3 1-150 (1974)

Copyright © 1974 American Chemical Society A l l Rights Reserved PRINTED I N T H E UNITED STATES O F AMERICA

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.fw001

ACS Symposium Series Robert F. Gould, Series Editor

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.fw001

FOREWORD The ACS SYMPOSIUM SERIES was founded in 1974 to provide

a medium for publishing symposia quickly in book form. The format of the SERIES parallels that of its predecessor, ADVANCES IN CHEMISTRY SERIES, except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. As a further means of saving time, the papers are not edited or reviewed except by the symposium chairman, who becomes editor of the book. Papers published in the ACS SYMPOSIUM SERIES are original contributions not published elsewhere in whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.pr001

PREFACE Twenty-five to thirty years ago widespread oxidant air pollution damage to ornamental and crop plants became apparent to both scientists and the public. This occurred first in the Los Angeles area, and it was predominantly associated with the large increase in industrial activity in the Los Angeles basin during the 1940's and 1950's. Research workers in and near Los Angeles, particularly at the California Institute of Technology at Pasadena and the University of California Agricultural Experiment Station at Riverside, conducted investigations to determine the cause and effect relationship between observed plant damage and environmental contaminants. Significant efforts were made to understand the complex atmospheric chemical and photochemical reactions leading to formulation of air pollutants identified in the atmosphere of the Los Angeles Basin. In later development of oxidant air pollution knowledge, automobile exhaust emissions and other fuel combustion processes were implicated as major factors in producing this class of air pollutants both in and near large metropolitan areas. In time, it became apparent that other areas in this country and throughout the world were experiencing similar oxidant air pollution episodes. Some of the pioneers in these early efforts to identify oxidants and understand the mechanisms of how they damage plants were A. J. HaagenSmit and F. W . Went and their colleagues at the California Institute of Technology, and John T. Middleton, Ellis F. Darley, and J. B. Kendrick, Jr. and their colleagues at the University of California Agricultural Experiment Station at Riverside. Substantial progress was made throughout the beginning years of air pollution research by these southern California researchers. Other research teams throughout the United States were also established to investigate plant responses to air pollution. Several of the major laboratories conducting early work in this research area were the USDA Laboratory at Beltsville, Md.; the Connecticut Agriculture Experiment Station at Windsor, Conn.; the National Center for Air Pollution Control, U . S. Department of Health, Education, and Welfare at Cincinnati, Oh.; and the University of Utah, Utah State University, Pennsylvania State University, and Rutgers University. During the 1950s and 1960s, significant advancement was made in determining chemical, meteorological, and biological knowledge regarding atmospheric oxidant damage to biological systems. ix

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.pr001

Within the past few years, the rate of our understanding of how air pollution oxidants intereet with biological systems has accelerated dra­ matically. This is the result partially of a reasonable level of federal grants and contract funds and partially of cooperative support by local and state agencies of research into specific pollution problems. Research supported by these agencies not only has helped establish an air pollution control policy, it has also helped develop a better scientific understanding of the biological effects of air pollution on man and plants. It was appropriate, therefore, that the Division of Agricultural and Food Chemistry hold a symposium on the topic of air pollution and equally appropriate that this meeting be held in Los Angeles. The papers in this volume describe not only some of the most recent ideas concerning this topic, but they also describe tests of these ideas by researchers who are second and third generation scientists in this field. In a sense, the questions asked by these more recent scientists do not differ significantly from those posed by the pioneers in air pollution studies; however, this does not imply that no progress has been made. As is the case with any area of scientific inquiry, questions often remain the same while answers change and become increasingly more complex. In this particular case, the complexity of the answers is attributable not only to the accumulation of new knowledge, but also to how critically important that new knowl­ edge is in its potential and actual effects on man and his environment. Future symposia on this subject will disclose still other answers to as yet unresolved questions. In time, however, we should understand much more completely the cause and effect relationship between oxidant air pollution and the mechanism of plant damage. The major photochemically-produced atmospheric pollutant is ozone and, accordingly, most of the papers in this volume are concerned with this oxidant and its effects on plant processes, plant constituents such as cellular membranes, or on biochemical reactions common to the biological systems of plants and animals. I believe these authors have significant new answers to old questions, and I applaud them for their contributions. I would like to thank Michael Elderman for his invaluable editorial assistance in the preparation of these manuscripts. M A C K DUGGER

Riverside, Calif. September 20, 1974

χ

1 Air Pollutant Effects Influenced by Plant-Environmental Interaction O. C. TAYLOR

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

Statewide Air Pollution Research Center, University of California, Riverside, Calif. 92502 S u s c e p t i b i l i t y o f vegetation t o air p o l l u t a n t i n j u r y is r e p o r t e d l y i n f l u e n c e d by many c l i m a t i c f a c t o r s , edaphic f a c t o r s , genetic variability, and by s t r u c t u r a l and biochemical v a r i a t i o n s i n the p l a n t . Observed d i f f e r e n c e s i n s u s c e p t i b i l i t y have prompted numerous attempts t o prepare lists o f p l a n t species according to s u s c e p t i b i l i t y or t o l e r a n c e to s p e c i f i c air pollut a n t s . I t has become apparent that such lists are f r e q u e n t l y inaccurate because the differential i n s u s c e p t i b i l i t y within a s i n g l e v a r i e t y or c u l t i v a r may be as great as t h a t between species. Accuracy o f t o l e r a n c e lists is f u r t h e r complicated by the f a c t t h a t data are o f t e n a v a i l a b l e from only one locality or from a s i n g l e experimental l a b o r a t o r y where one set o f e n v i r o n mental f a c t o r s i n t e r a c t with the p o l l u t a n t r e a c t i o n . Differences in p l a n t age, v a r i e t y , r a t e o f growth, light exposure, c l i m a t i c c o n d i t i o n s , n u t r i t i o n and other f a c t o r s can induce s i g n i f i c a n t v a r i a t i o n i n response to a p a r t i c u l a r p o l l u t a n t . The complex i n t e r a c t i o n between c l i m a t i c f a c t o r s , t o x i c a n t c o n c e n t r a t i o n , exposure d u r a t i o n , soil c o n d i t i o n s and physiological c h a r a c t e r i s t i c s determines the s u s c e p t i b i l i t y o f p l a n t t i s s u e and, t o a l a r g e extent, i n f l u e n c e s the c h a r a c t e r i s t i c s o f the i n j u r y symptom syndrome produced. D i s t i n c t and relatively uniform symptoms may be produced repeatedly on s u s c e p t i b l e members o f the p l a n t community if they are exposed under c o n t r o l l e d - s t a n d a r d i z e d c o n d i t i o n s . But the extent o f i n j u r y and a concomitant a l t e r a t i o n in i n j u r y appearance u s u a l l y occurs when there i s a d e v i a t i o n i n t o x i c a n t dosage, p l a n t species or e n v i ronmental c o n d i t i o n . Meteorological

Factors

L i g h t . Photoperiod has a marked e f f e c t on s u s c e p t i b i l i t y o f p l a n t s t o photochemical a i r p o l l u t a n t s . The e f f e c t o f photop e r i o d i s p a r t i c u l a r l y s t r i k i n g when peroxyacetyl n i t r a t e (PAN) i s the p r i n c i p a l t o x i c a n t , but there i s a l s o a s i g n i f i c a n t e f f e c t

1

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

2

ABR POLLUTION EFFECTS ON PLANT GROWTH

when o z o n e and n i t r o g e n d i o x i d e a r e u s e d a s p h y t o t o x i c a n t s . Juhren e t a l , (1) r e p o r t e d g r e a t e r s u s c e p t i b i l i t y o f annual b l u e g r a s s t o o x i d a n t w i t h an 8-hr p h o t o p e r i o d t h a n w i t h a 1 6 - h r p h o t o p e r i o d , where p l a n t s were grown u n d e r m o d e r a t e l i g h t i n t e n sity. Heck and D u n n i n g (2) and M a c D o w a l l (j3) a l s o f o u n d t h a t p l a n t s g r o w i n g u n d e r a s h o r t day ( 8 h r . ) were more s u s c e p t i b l e t h a n p l a n t s g r o w i n g under a 12 o r 16-hr/day r e g i m e . Generally, p l a n t s g r o w i n g c o n t i n u o u s l y u n d e r s h o r t - d a y c o n d i t i o n s a r e most s u s c e p t i b l e t o o x i d a n t s , b u t M a c D o w a l l ( 3 ) showed t h a t s u s c e p t i b i l i t y o f p l a n t s g r o w i n g u n d e r l o n g - d a y c o n d i t i o n s c o u l d be i n c r e a s e d b y a 3-day t r e a t m e n t w i t h 8 h r o f l i g h t p r i o r t o f u m i gation. T a y l o r et_ a l . ( 4 ) s u g g e s t e d t h a t i n t e r a c t i o n s b e t w e e n l i g h t and o x i d a n t s f r o m t h e p o l l u t e d a t m o s p h e r e w i t h i n p l a n t t i s s u e s m i g h t e x p l a i n n o t o n l y some o f t h e v a r i a b i l i t i e s i n symptomat o l o g y observed i n c o n t r o l l e d experiments but a l s o the unexp l a i n e d v a r i a b i l i t y o b s e r v e d i n some p o l l u t e d a r e a s . Why d i d e x p o s u r e t o PAN on one day f a i l t o p r o d u c e i n j u r y symptoms, and an e x p o s u r e o f t h e same c o n c e n t r a t i o n and d u r a t i o n on a n o t h e r day produce severe i n j u r y ? F u r t h e r i n v e s t i g a t i o n r e v e a l e d t h a t s u s c e p t i b i l i t y o f p i n t o b e a n and p e t u n i a p l a n t s t o PAN was s i g n i f i c a n t l y a f f e c t e d by t h e p r e s e n c e o f l i g h t i m m e d i a t e l y b e f o r e , d u r i n g and a f t e r e x p o s u r e t o t h e t o x i c a n t 5_). The l i g h t - d a r k i n t e r a c t i o n s w h i c h r e g u l a t e d s u s c e p t i b i l i t y o f b e a n p l a n t s t o PAN i n j u r y were d e s c r i b e d i n d e t a i l by T a y l o r (6). A p p r o x i m a t e l y 2.75 h r o f s u n l i g h t f o l l o w i n g a 1 2 - h r n i g h t was r e q u i r e d f o r f u l l s u s c e p t i b i l i t y t o d e v e l o p ; a 15 min d a r k p e r i o d b e f o r e a 30-min f u m i g a t i o n was s u f f i c i e n t t o g i v e c o m p l e t e p r o t e c t i o n . A f u l l h o u r o f s u n l i g h t f o l l o w i n g t h e 15-min d a r k t r e a t m e n t was r e q u i r e d t o r e g a i n c o m p l e t e s u s c e p t i b i l i t y . It is important t o recognize the e f f e c t o f s h o r t , dark exposures t o avoid e r r o r s i n i n t e r p r e t i n g response during fumigation s t u d i e s . A b r i e f s t a y i n d a r k n e s s o r v e r y l o w l i g h t i n t e n s i t y may be s u f f i c i e n t t o p r o v i d e a s i g n i f i c a n t amount o f t o l e r a n c e t o PAN. T a y l o r (6_) a l s o r e p o r t e d t h a t c o n t i n u e d e x p o s u r e t o s u n l i g h t f o r a b o u t 3 h r , f o l l o w i n g a 30-min f u m i g a t i o n , was r e q u i r e d f o r c o m p l e t e d e v e l o p m e n t o f PAN symptoms. P l a n t s p l a c e d i n a d a r k chamber i m m e d i a t e l y a f t e r a 30-min PAN t r e a t m e n t were n o t i n j u r e d . The d e l a y e d e f f e c t o f PAN was a l s o o b s e r v e d i n t h e R i v e r s i d e l a b o r a t o r y when an a t t e m p t was made t o measure c h a n g e s i n CO2 a b s o r p t i o n d u r i n g and f o l l o w i n g PAN t r e a t m e n t . Absorption r a t e , measured i n a dynamic f l o w system w i t h a n o n d i s p e r s i v e i n f r a r e d a n a l y z e r , d i d n o t change d u r i n g a o n e - h r f u m i g a t i o n p e r i o d o r d u r i n g 2.75 h r i m m e d i a t e l y f o l l o w i n g f u m i g a t i o n . A f t e r about 2.75 h r , w a t e r - s o a k e d a r e a s became f a i n t l y v i s i b l e , and CO2 a b s o r p t i o n d e c l i n e d a b r u p t l y t o a p p r o x i m a t e l y 50% o f t h e f o r m e r level. F u l l d e v e l o p m e n t o f t h e l o w e r s u r f a c e b r o n z i n g and c o l l a p s e d " b i f a c i a l " l e s i o n s o c c u r r e d d u r i n g t h e s u c c e e d i n g 36 h r . A i r p o l l u t a n t s a r e t r a n s p o r t e d w i t h w i n d movement; c o n s e q u e n t l y , e l e v a t e d c o n c e n t r a t i o n s may be moved f r o m one a r e a t o

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

1.

TAYLOR

Plant-Environment

Interaction

3

a n o t h e r . Peak c o n c e n t r a t i o n s o f o z o n e a n d PAN i n t h e e a s t e r n p a r t o f t h e South Coast A i r B a s i n o f C a l i f o r n i a u s u a l l y occur i n the afternoon and evening. I f t h e p o l l u t e d a i r mass r e a c h e s v e g e t a t i o n l a t e i n t h e e v e n i n g , PAN i n j u r y w i l l p r o b a b l y n o t develop even though t h e t h r e s h o l d c o n c e n t r a t i o n i s exceeded t h r o u g h t h e n i g h t (6)· Severe i n j u r y can be e x p e c t e d i f t h e p o l l u t a n t s reach t h e area s l i g h t l y e a r l i e r i n the day. P h o t o p e r i o d a l s o a f f e c t s t h e response o f p l a n t s t o ozone ( 7 ^ 8 ) . T i n g a n d Dugger (8) r e p o r t e d t h a t a f t e r a 2 4 - h r d a r k t r e a t m e n t , l e a v e s o f c o t t o n p l a n t s were n o l o n g e r s e n s i t i v e t o o z o n e . He p o i n t e d o u t t h a t r a d i a n t e n e r g y d u r i n g d e v e l o p m e n t c o r r e l a t e d w i t h s u s c e p t i b i l i t y o f c o t t o n t o ozone. Davis ( 7 ) f o u n d t h a t s e e d l i n g s o f V i r g i n i a p i n e were p r o t e c t e d f r o m i n j u r y when t h e y were k e p t i n l i g h t f o r 24 h r o r l o n g e r p r i o r t o e x p o s u r e t o damaging d o s e s o f o z o n e . They a l s o f o u n d t h a t p i n e s e e d l i n g s k e p t i n d a r k n e s s f o r up t o 96 h r p r i o r t o o z o n e e x p o s u r e were s u s c e p t i b l e t o i n j u r y . T h e s e c o n f l i c t i n g e x p e r i ences w i t h t h e p r o t e c t i v e e f f e c t o f p r e - f u m i g a t i o n dark t r e a t ments s u g g e s t t h a t f u r t h e r s t u d i e s may b e b e n e f i c i a l . Dugger e t a l . (5_) f o u n d t h a t s u s c e p t i b i l i t y o f y o u n g b e a n p l a n t s t o o z o n e was i n c r e a s e d b y d a r k p e r i o d s o f up t o 24 h r , b u t t h e t o l e r a n c e increased d r a m a t i c a l l y w i t h longer dark p e r i o d s . Heck (9_, 1 0 ) a n d h i s c o - w o r k e r s n o t e d t h a t J u h r e n et_ a l . ( 1 2 ) r e p o r t e d P o a annua p l a n t s were most s u s c e p t i b l e t o L o s A n g e l e s t y p e smog when t h e y were grown i n a s h o r t ( 8 - h r ) p h o t o p e r i o d a n d t h a t Dugger et^ a l . (5_) r e p o r t e d t h a t b e a n p l a n t s grown u n d e r 9 0 0 - f t - c l i g h t i n t e n s i t y were more s u s c e p t i b l e t h a n p l a n t s grown u n d e r 2 2 0 0 - f t - c . Consequently, they i n v e s t i g a t e d combinations o f photoperiod l e n g t h and l i g h t i n t e n s i t y and found g r e a t e s t s u s c e p t i b i l i t y o f bean and t o b a c c o p l a n t s t o ozone o c c u r r e d when t h e y were grown u n d e r l o w l i g h t i n t e n s i t y w i t h short photoperiod. O b s e r v a t i o n s have a l s o b e e n made t h a t e x tensive areas o fwhite o r l i g h t t a n n e c r o t i c l e s i o n s o f collapsed t i s s u e a r e common when p l a n t s a r e e x p o s e d t o o z o n e u n d e r l o w l i g h t i n t e n s i t y . T h i s b l e a c h i n g e f f e c t i s l e s s pronounced and t h e n e c r o t i c l e s i o n s a p p e a r d a r k brown o r r e d d i s h - b r o w n when p l a n t s a r e e x p o s e d u n d e r f u l l s u n l i g h t . An optimum l e v e l o f s u g a r ( s u c r o s e a n d r e d u c i n g s u g a r ) i n l e a f t i s s u e was r e q u i r e d t o i n d u c e maximum s u s c e p t i b i l i t y ( 1 1 , 1 2 , 1 3 ) . L e e ( 1 3 ) s u g g e s t e d t h a t t h e sugar content r e g u l a t e d stomatal opening and thus had a m a r k e d e f f e c t o n t h e amount o f i n j u r y . D u g g e r s g r o u p ( 1 1 , 1 2 ) p o s t u l a t e d t h a t t h e s u g a r r e l a t i o n t o t o l e r a n c e was more d i r e c t . 1

T e m p e r a t u r e . H i l l ert a l . ( 1 4 ) i n i t i a t e d s t u d i e s o f e f f e c t s o f s u l f u r d i o x i d e and mixtures o f s u l f u r d i o x i d e and n i t r o g e n d i o x i d e on d e s e r t v e g e t a t i o n b y t r a n s p l a n t i n g n a t i v e s p e c i e s t o the greenhouse, b u t they l a t e r concluded t h a t s e n s i t i v i t y v a r i e d g r e a t l y w i t h d i f f e r e n c e s i n s o i l moisture, r e l a t i v e humidity and t e m p e r a t u r e . C o n s e q u e n t l y , f u m i g a t i o n s were c a r r i e d o u t i n t h e f i e l d w i t h p l a n t s g r o w i n g u n d e r n a t u r a l c o n d i t i o n s . D a v i s (7_)

4

AIR

POLLUTION EFFECTS ON PLANT GROWTH

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

o b s e r v e d an i n v e r s e r e l a t i o n s h i p b e t w e e n e x p o s u r e t e m p e r a t u r e and d e g r e e o f i n j u r y on V i r g i n i a p i n e . C o n v e r s e l y , Cameron and T a y l o r (15) o b s e r v e d t h a t e l e v a t e d c o n c e n t r a t i o n s o f ozone i n t h e f i e l d p r o d u c e d l i t t l e o r no v i s i b l e symptoms i n sweet c o r n i f a m b i e n t a i r t e m p e r a t u r e s d u r i n g and a f t e r e x p o s u r e s were b e l o w a b o u t 90°F. S e v e r e i n j u r y o c c u r r e d on s u s c e p t i b l e v a r i e t i e s o f sweet c o r n when t e m p e r a t u r e e x c e e d e d 90°F. D a v i s ( 7 ) obs e r v e d a d i r e c t c o r r e l a t i o n b e t w e e n t h e amount o f o z o n e i n j u r y p r o d u c e d and t h e t e m p e r a t u r e a t w h i c h p i n e s e e d l i n g s were m a i n t a i n e d b e f o r e and a f t e r e x p o s u r e s . R e l a t i v e Humidity. Heggestad e t a l . (16) suggested t h a t the h i g h r e l a t i v e h u m i d i t y a l o n g t h e e a s t c o a s t o f t h e U. S. i n c r e a s e d s u s c e p t i b i l i t y o f p l a n t s t o ozone i n j u r y . The t o b a c c o g r o w i n g s p a c e s and f u m i g a t i o n chambers u s e d i n h i s i n v e s t i g a t i o n s were d e s i g n e d t o m a i n t a i n s a t u r a t e d a t m o s p h e r e d u r i n g a l l s t a g e s o f g r o w i n g and f u m i g a t i o n o f p l a n t s . The g r e a t e r amount o f o z o n e r e q u i r e d t o p r o d u c e o z o n e i n j u r y i n w e s t c o a s t f u m i g a t i o n s was a t t r i b u t e d t o the low r e l a t i v e h u m i d i t y i n t h a t a r e a . Efforts t o prove t h i s concept by u s i n g f o g n o z z l e s i n t h e p l a n t growing a r e a s and t h e u s e o f f o g n o z z l e s t o add w a t e r t o t h e a i r i n t a k e o f f u m i g a t i o n chambers u s e d a t R i v e r s i d e , C a l i f o r n i a d i d n o t c o n c l u s i v e l y confirm the theory. Increased tolerance of p l a n t s t o o z o n e has b e e n o b s e r v e d when f u m i g a t i o n s were c o n d u c t e d i n a i r d r i e r t h a n t h a t i n t h e g r o w i n g a r e a . When p l a n t s were t r a n s f e r r e d f r o m t h e g r e e n h o u s e t o f u m i g a t i o n chambers t h r o u g h t h e d r y a m b i e n t a i r a t R i v e r s i d e , s t o m a t a l c l o s u r e due t o t h e immed i a t e w a t e r s t r e s s was c o n s i d e r e d t o be t h e r e a s o n f o r t h e p r o nounced i n c r e a s e o f t o l e r a n c e under such c o n d i t i o n s . Davis (7) f o u n d t h a t p i n e s e e d l i n g s d e v e l o p e d more s e v e r e o z o n e i n j u r y when e x p o s e d i n h i g h h u m i d i t y t h a n when e x p o s e d i n l o w h u m i d ities. I n t h e i r s t u d i e s , h u m i d i t y b e f o r e and a f t e r e x p o s u r e t o 25 pphm o z o n e f o r 4 h r had no e f f e c t upon t h e amount o f i n j u r y p r o d u c e d . M a c D o w e l l ( 1 7 ) r e p o r t e d t h a t t o b a c c o was more s u s c e p t i b l e t o o z o n e when dew was on t h e l e a v e s t h a n when t h e y were dry. T h e r e i s no c o n c l u s i v e e x p e r i m e n t a l e v i d e n c e t h a t r e l a t i v e h u m i d i t y s i g n i f i c a n t l y a f f e c t s s u s c e p t i b i l i t y o f p l a n t s t o PAN as l o n g a s c o n d i t i o n s a r e s u c h t h a t t h e s t o m a t a r e m a i n o p e n . There have been s u g g e s t i o n s , however, t h a t h i g h r e l a t i v e h u m i d i t y may c a u s e r a p i d b r e a k d o w n o f PAN ( 1 8 ) b u t t h e r e i s no e x p e r i mental evidence t o support such a statement. In the South Coast A i r B a s i n o f C a l i f o r n i a , PAN i n j u r y t o v e g e t a t i o n o c c u r s most f r e q u e n t l y when r e l a t i v e h u m i d i t y i s 50% o r above and e l e v a t e d c o n c e n t r a t i o n s o f 10 t o 30 ppb o f t e n p e r s i s t a l l n i g h t , w i t h r e l a t i v e h u m i d i t y above 60%. E d a p h i c F a c t o r s . S o i l t e x t u r e , s o i l m o i s t u r e and m i n e r a l n u t r i e n t s s t r o n g l y i n f l u e n c e p l a n t g r o w t h a n d , c o n s e q u e n t l y , have an e f f e c t on s u s c e p t i b i l i t y t o a i r p o l l u t a n t s . A d e q u a t e s o i l moisture to maintain l e a f t u r g i d i t y i s e s s e n t i a l to maintain f u l l

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

1.

TAYLOR

Fiant-Environment

Interaction

5

s u s c e p t i b i l i t y o f p l a n t s . F i e l d observations i n southern C a l i f o r n i a , where i r r i g a t i o n i s e s s e n t i a l f o r c r o p p r o d u c t i o n , h a v e r e v e a l e d t h a t c r o p s grown u n d e r s o i l m o i s t u r e d e f i c i t d e v e l o p e d l i t t l e o r n o o z o n e o r PAN t y p e symptoms d u r i n g a s e v e r e smog a t t a c k , w h i l e a d j a c e n t r e c e n t l y - i r r i g a t e d c r o p s were s e v e r e l y i n j u r e d . W i t h h o l d i n g i r r i g a t i o n has been suggested a s a t e c h n i q u e f o r p r e v e n t i n g o x i d a n t a i r p o l l u t a n t damage ( 1 9 ) . One m i g h t be f o r t u n a t e i f a smog a t t a c k o f a s i n g l e d a y ' s d u r a t i o n s h o u l d c o i n c i d e w i t h a p e r i o d when t h e f i e l d i s d r y , b u t t h e damage c a u s e d b y w i t h h o l d i n g w a t e r i n a n t i c i p a t i o n o f a smog a t t a c k c o u l d be a s i n j u r i o u s t o t h e c r o p a s t h e a i r p o l l u t a n t . Seidman e t a l . ( 2 0 ) f o u n d t h a t w a t e r c o u l d be w i t h h e l d f r o m p e t u n i a , t o b a c c o and p i n t o bean t o the p o i n t j u s t s h o r t o f w i l t ing t o c l o s e stomata and prevent i n j u r y from i r r a d i a t e d autom o b i l e e x h a u s t . M a c D o w a l l ( 3 ) r e p o r t e d t h a t t o b a c c o grown f o r s e v e r a l days w i t h d e f i c i e n t s o i l m o i s t u r e , b u t j u s t s h o r t o f w i l t i n g , were l e s s s u s c e p t i b l e t o o z o n e t h a n n o r m a l p l a n t s e v e n t h o u g h t h e y were w e l l w a t e r e d j u s t p r i o r t o e x p o s u r e . Similarly, i n c r e a s e d t o l e r a n c e o f b e a n s a n d t o b a c c o t o o z o n e a n d PAN h a s b e e n n o t e d when t e s t p l a n t s were i n a d v e r t a n t l y a l l o w e d t o w i l t b r i e f l y d u r i n g the day p r e c e d i n g f u m i g a t i o n , even though t h e y were w e l l w a t e r e d s e v e r a l h o u r s b e f o r e t r e a t m e n t a n d a p p e a r e d t o be n o r m a l . E x c e s s i v e s o i l w a t e r f o r a n e x t e n d e d p e r i o d may r e d u c e s u s c e p t i b i l i t y o f p l a n t s t o ozone i n j u r y . S t o l z y et_ a l . ( 2 1 ) showed t h a t o x y g e n d e f i c i e n c y i n t h e r o o t z o n e i n c r e a s e d o z o n e t o l e r a n c e o f t o m a t o p l a n t s . The l o w p a r t i a l p r e s s u r e o f o x y g e n i n t h e r o o t zone a l s o r e d u c e d w a t e r u p t a k e and p l a n t v i g o r . Seidman ert a l . ( 2 0 ) f o u n d t h a t p l a n t v i g o r a n d s u s c e p t i b i l i t y t o o z o n e were l e s s w i t h p l a n t s grown i n c l a y s o i l s r a t h e r t h a n i n v e r m i c u l i t e ; s i m i l a r l y , v i g o r a n d s u s c e p t i b i l i t y o f p l a n t s grown i n c l a y l o a m was s u p p r e s s e d compared t o p l a n t s grown i n a p e a t p e r l i t e mix. Nutrition. M i d d l e t o n (19) r e p o r t e d t h a t s p i n a c h and l e t t u c e were more s u s c e p t i b l e t o o z o n a t e d hexene when t h e y r e c e i v e d a n adequate supply o f n i t r o g e n f e r t i l i z e r . O t h e r s have a l s o r e p o r t e d i n c r e a s e d s u s c e p t i b i l i t y t o o x i d a n t s when n i t r o g e n f e r t i l i z e r was a p p l i e d ( 2 2 , 2 3 ) . T h e r e h a v e b e e n some r e p o r t s t h a t i n d i c a t e d a i r p o l l u t a n t i n j u r y was g r e a t e s t i n t e s t s w i t h t h e l e a s t amount o f n i t r o g e n a d d e d (3j 1 0 , 2M). T h i s s u g g e s t s t h a t i n j u r y was e n h a n c e d b y t h e a d d i t i o n o f n i t r o g e n when t h e r e was a d e f i c i e n c y b u t a l u x u r y amount d i d n o t i n c r e a s e i n j u r y a n d p e r haps even s u p p r e s s e d growth t o the p o i n t o f i n d u c i n g g r e a t e r tolerance. O e r t l i (25) r e p o r t e d i n c r e a s e d t o l e r a n c e o f s u n f l o w e r p l a n t s t o o x i d a n t a i r p o l l u t a n t s (smog) w i t h i n c r e a s i n g s a l i n i t y a n d s o i l m o i s t u r e s t r e s s . However, Heck e t a l . (9^, 1 0 ) s u g g e s t e d t h a t O e r t l i was d e a l i n g w i t h a n u t r i e n t a s w e l l a s o s m o t i c effect.

6

AIR

POLLUTION EFFECTS ON PLANT GROWTH

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

Mixtures of Toxicants. P o l l u t e d atmospheres are complex m i x t u r e s o f many t o x i c and i n e r t m a t e r i a l s w h i c h may i n t e r a c t t o i n c r e a s e o r d i m i n i s h p l a n t i n j u r y . Menser and H e g g e s t a d ( 2 6 ) r e p o r t e d t h e f i r s t e v i d e n c e o f s y n e r g i s t i c r e s p o n s e when an o z o n e - s u s c e p t i b l e t o b a c c o s t r a i n was e x p o s e d t o a m i x t u r e o f o z o n e and s u l f u r d i o x i d e . O t h e r r e s e a r c h e r s have s u b s e q u e n t l y c o n f i r m e d t h i s response, but attempts t o i d e n t i f y s y n e r g i s t i c or antagon i s t i c r e s p o n s e s w i t h o t h e r p o l l u t a n t s have been u n s u c c e s s f u l , a l t h o u g h s y n e r g i s t i c e f f e c t s o f NO2 and SO2 a r e s u g g e s t e d . F u r t h e r s t u d y o f t h e p o s s i b l e i n t e r a c t i o n o f p o l l u t a n t s w o u l d be d e s i r a b l e to help e x p l a i n v a r i a t i o n s i n plant response i n different locations. D i s c u s s i o n and Summary. G e n e t i c v a r i a b i l i t y i s a m a j o r determinant of plant tolerance to a i r p o l l u t a n t s . Differences i n s u s c e p t i b i l i t y b e t w e e n s p e c i e s o r g e n e r a a r e w e l l known, b u t s i g n i f i c a n t v a r i a t i o n between i n d i v i d u a l s w i t h i n a v a r i e t y o r c u l t i v a r has b e e n l e s s o b v i o u s . T o l e r a n c e and c h a r a c t e r i s t i c s o f symptoms a r e a l s o d e p e n d e n t upon t h e way e x p o s u r e t o t h e p o l l u tants occur. Exposure t o high concentrations o f a t o x i c p o l l u t a n t u s u a l l y p r o d u c e s symptoms q u i t e d i f f e r e n t f r o m t h o s e p r o d u c e d by l o n g exposure t o low c o n c e n t r a t i o n s . Heck and D u n n i n g (:2, 10) r e p o r t e d t h a t p l a n t s u s c e p t i b i l i t y was g r e a t e r when e x p o s e d t o a g i v e n d o s e o f o z o n e i n one h r t h a n when t h e same d o s e was applied i n m u l t i p l e exposures. A number o f e x t e r n a l and i n t e r n a l f a c t o r s a r e i n f l u e n t i a l i n d e t e r m i n i n g t h e s u s c e p t i b i l i t y o f a s p e c i f i c p l a n t t o an a i r b o r n e toxicant. Some g e n e r a l i z a t i o n s can be s t a t e d r e l a t i v e t o f a c t o r s that a f f e c t s u s c e p t i b i l i t y to oxidant a i r p o l l u t a n t s : a. Rapid-vigorous growth u s u a l l y i n c r e a s e d s u s c e p t i b i l i t y . b. P l a n t s grown i n i n t e n s e l i g h t a r e more s u s c e p t i b l e t o PAN. c. Low l i g h t i n t e n s i t y e n h a n c e d s u s c e p t i b i l i t y t o o z o n e . d. A l o n g d a r k p e r i o d (24 h r ) p r i o r t o e x p o s u r e i n c r e a s e d ozone s u s c e p t i b i l i t y . e. L i g h t b e f o r e and a f t e r e x p o s u r e t o PAN i s r e q u i r e d f o r i n j u r y development. f . A l o n g p h o t o p e r i o d (24 h r ) b e f o r e e x p o s u r e i n h i b i t e d ozone i n j u r y . g. High temperature d u r i n g exposure i n the f i e l d increased ozone s u s c e p t i b i l i t y . h. H i g h r e l a t i v e h u m i d i t y i n c r e a s e d s u s c e p t i b i l i t y t o ozone and PAN. i. S o i l moisture d e f i c i e n c y reduced s u s c e p t i b i l i t y t o ozone, PAN and SO2. j· S a l i n i t y r e d u c e d s u s c e p t i b i l i t y t o ozone· k. High n u t r i e n t s (nitrogen) g e n e r a l l y increased susceptibility. 1. S o i l oxygen d e f i c i e n c y reduced s u s c e p t i b i l i t y .

1.

TAYLOR

Phnt-Enxrironment

Interaction

7

Literature Cited

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch001

1.

J u h r e n , Μ., W. M. N o b l e a n d F. W. Went. P l a n t Physiol. ( 1 9 5 7 ) 32:576-586. 2. H e c k , W. W. a n d J. A. D u g g i n g . J. Air Pollut. C o n t r . A s s o c . ( 1 9 6 7 ) 17:112-114. 3. M a c D o w e l l , F. D. H. C a n . J. Plant Sci. ( 1 9 6 5 ) 45:1-12. 4. T a y l o r , O. C., W. M. D u g g e r , Jr., E . A. Cardiff a n d E . F. Darley. N a t u r e . ( 1 9 6 1 ) 192:814-816. 5. D u g g e r , W. Μ., Jr., O. C. Taylor, C. R. Thompson a n d E . Cardiff. J. Air Pollut. C o n t r . A s s o c . ( 1 9 6 3 ) 13:423-428. 6. T a y l o r , O. C. J. Air Pollut Contr. A s s o c . ( 1 9 6 9 ) 19(5):347-351. 7. D a v i s , D. D. Ph.D. T h e s i s , The P a . State University, University Park, PA 93p. ( 1 9 7 0 ) . 8. T i n g , I. P., a n d W. M. D u g g e r , Jr. J. Air Pollut. C o n t r . A s s o c . ( 1 9 6 8 ) 18:810-813. 9. H e c k , W. W. Ann. Rev. P h y t o p a t h ( 1 9 6 8 ) 6:165-188. 1 0 . H e c k , W. W. a n d J. A. D u n n i n g a n d I. J. H i n d a w i . J. Air Pollut. C o n t r . A s s o c . ( 1 9 6 5 ) 15:511-515. 1 1 . D u g g e r , W. Μ., Jr., O. C. Taylor, E. Cardiff a n d C. R. Thompson. P r o c . Am. S o c . H o r t . Sci. ( 1 9 6 2 ) 81:304-15. 1 2 . D u g g e r , W. M. a n d I. P. Ting. Ann. Rev. Plant Physiol. ( 1 9 7 0 ) 21:215-234. 1 3 . L e e , T. T. C a n . J. Bot. ( 1 9 6 5 ) 43:677-685. 14. Hill, A. C., S. Hill, C. Lamb a n d T. W. Barrett. J. Air Pollut. C o n t r . A s s o c . (1974) 24(2):153-157. 1 5 . Cameron, J. W. a n d O. C. Taylor. J. Environ. Q u a l . ( 1 9 7 3 ) 2(3):387-389. 1 6 . H e g g e s t a d , H. E . , F. R. Burleson, J. T. Middleton, a n d E. F. Darley. Inter. J. Air Water Pollut. ( 1 9 6 4 ) 8:1-10. 17. M a c D o w e l l , F. D. H. C a n . J. Plant Sci. ( 1 9 6 6 ) 46:349-353. 1 8 . T e n H o u t e n , J. G. " C h e m i c a l s , e n v i r o n m e n t a l pollution, animals and plants." Mededlingen Fakultett Landbouwwetenschappen, G e n t . ( 1 9 7 3 ) 38:511-612. 1 9 . M i d d l e t o n , J. T. J. Air Pollut. C o n t r . A s s o c . ( 1 9 5 6 - 5 7 ) 6:7-9. 20. S e i d m a n , G., I. J. H i n d a w i a n d W. W. Heck. J. Air Pollut. C o n t r . A s s o c . ( 1 9 6 5 ) 15:168-170. 21. Stolzy, L . H., O. C. Taylor, J. L e t e y a n d T. E . Szuszkiewicz. Soil Sci. ( 1 9 6 1 ) 91:151-155. 22. B r e w e r , R. F., F. B. Guillemet a n d R. K. Creveling. Soil Sci. ( 1 9 6 1 ) 92:298-301. 23. L e o n e , I. Α., E . G. B r e n n a n a n d R. H. Danes. J. Air Pollut. C o n t r . A s s o c . ( 1 9 6 6 ) 16:191-196. 24. M e n s e r , H. A. a n d O. E . Street. T o b a c c o Sci. ( 1 9 6 2 ) 6:167-171. 25. Oertli, J. J. Soil Sci. ( 1 9 5 8 ) 87:249-251. 26. M e n s e r , H. A. a n d H. E. H e g g e s t a d . S c i e n c e ( 1 9 6 6 ) 153:424-425.

2 Effect of Ozone on Plant Cell Membrane Permeability IRWIN P. TING, JOHN PERCHOROWICZ,

and LANCE EVANS

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch002

Department of Biology, University of California, Riverside, Calif. 92502

General E f f e c t s Ozone, a strong oxidant component o f photochemical smog i s r e a d i l y formed under c o n d i t i o n s o f high r a d i a t i o n and hydrocarbon waste. Oxides o f n i t r o g e n , mainly n i t r o g e n d i o x i d e a r i s i n g from high temperature combustion processes, r e a c t with molecular oxygen i n the atmosphere i n the presence o f u l t r a v i o l e t s u n l i g h t t o produce n i t r o g e n oxide and ozone. When excess hydrocarbons are present the n i t r o g e n oxide product (NO) will be converted to n i t r o g e n d i o x i d e , r e s u l t i n g i n high ozone l e v e l s ( 1 ) .

The t o x i c e f f e c t s o f ozone i n p l a n t systems have been studied f o r some time, y e t the a c t u a l mechanisms o f i n j u r y are not fully understood. In a d d i t i o n t o visible n e c r o s i s which appears l a r g e l y on upper l e a f s u r f a c e s , many other p h y s i o l o g i c a l and biochemical e f f e c t s have been recorded ( 2 ) . One o f the first e a s i l y measurable e f f e c t s is a s t i m u l a t i o n o f r e s p i r a t i o n . Frequently, however, r e s p i r a t i o n may not increase without concomitant v i s i b l e i n j u r y . Furthermore, photosynthesis in green leaves as measured by CO2 a s s i m i l a t i o n , may decrease. I t is w e l l known that ozone exposure i s accompanied by a dramatic i n c r e a s e i n f r e e p o o l amino a c i d s ( 3 ) . Ordin and h i s co-workers (4) have c l e a r l y shown the e f f e c t o f ozone on cell w a l l b i o s y n t h e s i s . In a d d i t i o n , ozone is known to o x i d i z e c e r t a i n lipid components o f the cell ( 5 ) , to a f f e c t ribosomal RNA (6) and to a l t e r the f i n e s t r u c t u r e o f chloroplasts (7). In a d d i t i o n t o these e f f e c t s , there i s much evidence to suggest that ozone s i g n i f i c a n t l y a l t e r s the p e r m e a b i l i t y properties of cell membranes. In f a c t , Rich (8) proposed that a primary

8

2.

TING ET AL.

Cell Membrane

Permeability

θ

e f f e c t o f o z o n e was t h e d e s t r u c t i o n o f membrane s e m i - p e r m e a b i l i t y . As e a r l y a s 1 9 5 5 , Wedding a n d E r i c k s o n ( 9 ) o b s e r v e d a n a l t e r e d phosphate and water p e r m e a b i l i t y i n p l a n t c e l l s exposed t o ozona t e d h e x e n e . Dugger a n d P a l m e r ( 1 0 ) , s t u d y i n g r o u g h l e m o n l e a v e s exposed t o ozone, found a d e f i n i t e a l t e r a t i o n i n p e r m e a b i l i t y t o g l u c o s e ; a f t e r a c u t e e x p o s u r e t o o z o n e , t h e r e was a s t e a d y i n ­ c r e a s e d u p t a k e o f g l u c o s e b y t r e a t e d l e a v e s compared t o t h a t i n controls. The e x p o s e d l e a v e s a b s o r b e d a p p r o x i m a t e l y t w i c e a s much g l u c o s e a s u n t r e a t e d l e a v e s a f t e r s i x d a y s . The i n c r e a s e d u p t a k e a t t r i b u t a b l e t o o z o n e e x p o s u r e was due s o l e l y t o a n i n c r e a s e i n g l u c o s e - U - * C p e r m e a b i l i t y a n d was n o t t h e r e s u l t o f i n t e r n a l i n c r e a s e d g l u c o s e u t i l i z a t i o n s i n c e t h e r e was n o d i f f e r e n c e i n ^*C02 r e l e a s e f r o m c o n t r o l s a n d e x p o s e d t i s s u e s . In a d d i t i o n t o s t u d i e s w i t h whole c e l l s and t i s s u e s , i t has a l s o b e e n shown t h a t t h e p e r m e a b i l i t y o f i s o l a t e d o r g a n e l l e s c a n b e a l t e r e d b y o z o n e e x p o s u r e . F o r e x a m p l e , L e e ( 1 1 ) showed t h a t ozone a l t e r e d t h e p e r m e a b i l i t y o f tobacco m i t o c h o n d r i a , and C o u l s o n a n d H e a t h ( 1 2 ) r e p o r t e d membrane p e r m e a b i l i t y c h a n g e s o f i s o l a t e d c h l o r o p l a s t s a f t e r ozone e x p o s u r e .

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch002

ll

Cell Permeability Age E f f e c t s . We have f o u n d i t u s e f u l t o d i s t i n g u i s h b e t w e e n t h e t e r m s " s u s c e p t i b l e " a n d " s e n s i t i v e " a n d t h u s , have d e f i n e d t h e a g e o f maximum i n j u r y p o t e n t i a l a s t h e s u s c e p t i b l e age. V a r i a t i o n s i n the degree o f i n j u r y d u r i n g the s u s c e p t i b l e stage are r e f e r r e d t o i n terms o f s e n s i t i v i t y . Susceptible leaves w i l l vary i n s e n s i t i v i t y p r i m a r i l y as a f u n c t i o n o f environmental differences. The a g e - s u s c e p t i b i l i t y phenomenon t o o x i d a n t i n j u r y i s shown i n F i g u r e 1. Young e x p a n d i n g l e a v e s p a s s t h r o u g h a s t a g e at which they are maximally s u s c e p t i b l e t o o x i d a n t i n j u r y . N e i t h e r young nor o l d l e a v e s a r e p a r t i c u l a r l y a f f e c t e d b y ozone, though o n l y young l e a v e s a r e s u s c e p t i b l e t o p e r o x y a c e t y l n i t r a t e (PAN) i n j u r y ( 2 ) . S e n s i t i v i t y o f a s u s c e p t i b l e l e a f c a n be markedly a l t e r e d by s h i f t s i n environmental c o n d i t i o n s such a s l i g h t , water and n u t r i t i o n . D e s p i t e the l a c k o f v i s i b l e n e c r o s i s o f young a n d o l d l e a v e s , i t i s p o s s i b l e t o demonstrate a l t e r a t i o n s i n c e l l p e r m e a b i l i t y by f o l l o w i n g m e t a b o l i t e uptake a f t e r ozone e x p o s u r e . I f A c a l a SJ-1 c o t t o n l e a v e s a r e e x p o s e d t o o z o n e a n d a l l o w e d t o t a k e up s u c r o s e 24 h r l a t e r , t h e r e i s n e a r l y a d o u b l i n g o f t h e r a t e o f s u c r o s e uptake b y l e a v e s which are maximally s u s c e p t i b l e t o ozone. However, b o t h y o u n g a n d o l d l e a v e s w h i c h show no v i s i b l e i n j u r y do show a b o u t a 5 0 % i n c r e a s e i n s u c r o s e u p t a k e ( T a b l e I ) . T h e s e d a t a s u g g e s t t h a t b o t h y o u n g a n d o l d t i s s u e a r e i n j u r e d t o some e x t e n t by ozone.

10

AIR

Table I .

Age

1 4

U p t a k e o f s u c r o s e - U - C by c o t t o n leaf discs

of cotyledon (days) 7 14 21

POLLUTION EFFECTS ON PLANT GROWTH

(Acala

Ratio 0 /control* ο

SJ-1)

Visible injury**

1.49 2.13 1.48

No Yes No

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch002

* R a t i o o f s u c r o s e u p t a k e by ozone exposed d i s c s t o u p t a k e control discs.

by

* * V i s i b l e i n j u r y a s s e s s e d by o b s e r v a t i o n o f n e c r o s i s on l e a f surface. P l a n t s were e x p o s e d t o 0.5 ppm 0 f o r 1 h r , 24 h r s p r i o r t o the experiment. 3

Amino A c i d U p t a k e . I f s u s c e p t i b l e l e a v e s a r e e x p o s e d t o o z o n e and t h e n i n c u b a t e d i n l e u c i n e - U - ^ C , t r e a t e d l e a v e s a b s o r b t h i s amino a c i d a t a f a s t e r r a t e t h a n c o n t r o l s ( F i g . 2 ) . I f , a f t e r 4 hr o f continuous uptake the ^ C - l e u c i n e i s f o l l o w e d w i t h nonlabelled leucine, a s i g n i f i c a n t d i f f e r e n t i a l u t i l i z a t i o n of the i n c o r p o r a t e d l e u c i n e i s not observed ( F i g . 2 ) . T h i s suggests t h a t t h e g r e a t e r u p t a k e i s n o t a c o n s e q u e n c e o f more r a p i d u t i l i z a t i o n and t h a t i t i s p r o b a b l y a t t r i b u t a b l e t o i n c r e a s e d permeability. D e s p i t e a s i g n i f i c a n t l y g r e a t e r u p t a k e o f - ^ C - l e u c i n e by ozonated t i s s u e , greater i n c o r p o r a t i o n of l e u c i n e i n t o p r o t e i n does not appear t o o c c u r . When i n c o r p o r a t i o n i n t o p r o t e i n i s e x p r e s s e d a s a p e r c e n t a g e o f l ^ C a c t u a l l y t a k e n u p , t h e r e i s no d i f f e r e n c e b e t w e e n t h e u n t r e a t e d and o z o n e - t r e a t e d t i s s u e ( T a b l e I I ) . These d a t a f u r t h e r s u p p o r t t h e n o t i o n t h a t enhanced u p t a k e i s s o l e l y a f u n c t i o n o f i n c r e a s e d t r a n s p o r t and n o t o f increased i n t e r n a l u t i l i z a t i o n . S i n c e t h e k i n e t i c s o f l e u c i n e u p t a k e a p p e a r t o be e x p o n e n ­ t i a l , a s t r a i g h t l i n e i s o b t a i n e d when t h e l o g o f u p t a k e i s p l o t t e d a g a i n s t t h e l o g o f t i m e ( F i g . 3 ) . The c o n s t a n t s l o p e and the lower y - i n t e r c e p t i n d i c a t e a higher uptake i n ozone-treated t i s s u e compared w i t h u n t r e a t e d t i s s u e . C a r b o h y d r a t e Uptake. Immediately a f t e r ozone e x p o s u r e , t r e a t e d b e a n l e a v e s a r e o b s e r v e d t o t a k e up l e s s g l u c o s e - U - ^ C than untreated leaves. A f t e r a few h o u r s , h o w e v e r , t h e o z o n e t r e a t e d l e a v e s b e g i n t o a s s i m i l a t e s i g n i f i c a n t l y more g l u c o s e . S i m i l a r l y , i f the nonmetabolizable carbohydrate 2-deoxyglucose i s s u p p l i e d t o o z o n e - t r e a t e d l e a v e s , enhanced uptake o c c u r s ( F i g . 4 ) . I m m e d i a t e l y f o l l o w i n g o z o n e e x p o s u r e 25% l e s s 2 - d e o x y g l u c o s e i s t a k e n up by o z o n e - t r e a t e d t i s s u e , b u t a f t e r 4 h r n e a r l y 50% more

2.

TING ET AL.

Cell Membrane Permeability

11

20

100

80

Ο

H60 S

ω ζ

OC

< 10 Ο­ Χ

3

Publication Date: June 1, 1974 | doi: 10.1021/bk-1974-0003.ch002