Photosynthesis, Photorespiration, and Plant Productivity PDF
Preview Photosynthesis, Photorespiration, and Plant Productivity
PHOTOSYNTHESIS, PHOTORESPIRATION, AND PLANT PRODUCTIVITY ISRAEL ZELITCH Department of Biochemistry The Connecticut Agricultural Experiment Station New Haven, Connecticut Academic Press 1971 New York and London COPYRIGHT © 1971, BY ACADEMIC PRESS, INC. ALL RIGHTS RESERVED NO PART OF THIS BOOK MAY BE REPRODUCED IN ANY FORM BY PHOTOSTAT, MICROFILM, RETRIEVAL SYSTEM, OR ANY OTHER MEANS, WITHOUT WRITTEN PERMISSION FROM THE PUBLISHERS. ACADEMIC PRESS, INC. Ill Fifth Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. 24/28 Oval Road, London NW1 7DD LIBRARY OF CONGRESS CATALOG CARD NUMBER :70-154386 PRINTED IN THE UNITED STATES OF AMERICA Preface In this book I have attempted to provide advanced undergraduates, graduate students, teachers, and research workers in a number of disciplines with a perspective of photosynthesis and how it may be increased. Thus many processes other than photosynthesis that affect the productivity of plants have been examined from the standpoint of enzyme chemistry, chloroplasts, leaf cells, and single leaves. Finally, the function of all of these in a stand of plants growing outdoors and subject to the overriding influence of climate has been considered. I have had to deal with elements of physics, biochemistry, plant physiology, genetics, climatology, agronomy, and other sciences to varying degrees. Wherever possible I have tried to evaluate our more recent knowledge, to point out areas of uncertainty, and to indicate promising approaches for future investigation. Examples were taken from higher plants when they were available, although studies with algae and photosynthetic bacteria have also been examined. Most of this book deals with the advances of the sixties, but sufficient historical background is provided so that the foundations on which this ix χ Preface knowledge was based may be fully appreciated. The past decade may be remembered for the Green Revolution in which agricultural scientists demonstrated that with an input of suitable genetic material and increased nutrient supply the yield of certain crops which had only doubled in the previous one hundred years was at least doubled again. But scientists believe that the next large increases in productivity must come from the application of the newer findings about photosynthetic carbon assimila- tion. Fortunately, research during the last decade has created impressive advances in our understanding of these processes. Some of the newer and often unexpected knowledge revealed during the sixties that I have considered includes the realization that rates of enzymatic reactions are often controlled by small regulator molecules; findings about the detailed structure and function of chloroplasts and other organelles and their variability; substantial evidence that photosynthesis requires at least two separate photoacts; the unraveling of many details about the mechanism of photosynthetic electron transport and photophosphoryla- tion; the appreciation of the importance of diffusive resistances to carbon dioxide assimilation, especially the role of stomata; the grasping of the importance of dark respiration in diminishing productivity; the discovery that the great differences in net photosynthesis that occur between many species and varieties is largely caused by a newly recognized type of respira- tion—photorespiration turned on by light; and the coping with the com- plexities of illumination and climate within the real canopies made by the leaves of crops that feed us. Readers may wonder how a biochemist became interested in these diverse subjects and even learned the language used by investigators in other disciplines. For this I must thank my colleagues at The Connecticut Agricultural Experiment Station with whom I have had the opportunity to discuss these important problems for many years. Thus by sometimes asking what might have appeared to be "foolish" questions, in due course I began to converse about these subjects relatively painlessly. By sharing the fruits of these conversations with readers, it is my fondest hope that we may be able to work together more easily in order to alleviate the widespread suffering that will otherwise result from an inadequate world food supply. ISRAEL ZELITCH Acknowledgments The orderly completion of this book involved the cooperation of a number of people. I wish to thank Dr. Graham Berlyn, Dr. Vernon E. Gracen, Jr., Mr. Fritz Goro, and Dr. Eldon H. Newcomb for providing illustrations, some of them before publication. Material in advance of publication was also received from Dr. William A. Jackson, Dr. Jack Preiss, and Dr. Peter Trip. Dr. Paul E. Waggoner kindly supplied unpublished data that was used extensively in Chapter 9. Miss M. Gregory, Jodrell Laboratory, Royal Botanic Garden, Kew, England, provided an analysis of earlier investigations about chloroplasts in the bundle-sheath cited in a footnote in Chapter 2. Friendly critics in several departments of The Connecticut Agricultural Experiment Station (and nearby) offered suggestions about various chapters: Dr. Peter R. Day, Dr. Kenneth R. Hanson, Dr. Evelyn A. Havir, Dr. Jean-Yves Parlange (Engineering and Applied Science, Yale University), Dr. Raymond P. Poincelot, Jr., Dr. Ernest G. Uribe (Biology Department, Yale University), and Dr. Paul E. Waggoner. Two colleagues read the entire xi xii Acknowledgments manuscript at one or more stages, and thus I am especially grateful for the counsel of Dr. Η. B. Vickery (Biochemist Emeritus) and Dr. Gary Heichel (Department of Ecology and Climatology). I have been greatly helped in many ways by Mrs. Ruth DiLeone, who drafted most of the figures and also typed the manuscript, and by Mr. John A. Marcucci, who assisted with library searches. Conversion Units LIGHT AND ENERGY Illumination of 1 foot candle (ft-c) = 10.764 lumens m"2 (lux) Total maximum incident sunlight = 10,000 ft-c = 108,000 lux 1 watt = 107 erg sec-1 1 cal = 4.186 χ 107ergs Maximum incident solar irradiation at earth's surface = 1.2 cal cm"2 min"1 1 watt m"2 = 103 erg sec"1 cm"2 = 1.43 χ 10"3 cal cm"2 min"1 (400 to 700 nm) Maximum visible solar irradiation (400 to 700 nm) = 0.6 cal cm -2 min"1 = 42 χ 104 erg sec"1 cm"2 = about 9 iieinsteins cm"2 min"1 absorbed by an average leaf OTHER CONVERSIONS 1 nm = 10"9 m = 1 ιημ = 10 Angstrom (A) ppm of C0 = μΐ per liter by volume 2 xiii xiv Conversion Units 300 ppm of C0 = about 9 χ 10 ~6 Μ free C0 in solution in pure water 2 2 1 acre = 2.47 hectare (ha) or 2.47 χ 104 m2 1 pound per acre = 1.12 kg ha-1 Wind speed of 100 cm sec"1 = 2 miles per hour AVERAGE LEAF COMPOSITION 1 dm2 projected area = 2.0 gm fresh weight of lamina = 3.0 mg chloro- phyll = 6 mg protein Ν = 40 mg protein 1 Morphology of Leaf Cells An aim of this monograph is to provide a basis for understanding the main factors concerned with regulating plant productivity in communities of plants. However, before one can evaluate how plants function in a stand, it is first necessary to examine the biochemical, physiological, and physical activities of single leaves. Hence it becomes necessary to study the nature of the kinds of cells in leaf tissues as well as the organelles they contain, and to examine especially the biochemical and physiological functions associated with these various parts. Leaf cells possess the fundamental capabilities and carry out the processes common to all other living cells, but perhaps of greater importance in this discussion are the unique properties not encountered elsewhere. Some of these special attributes include the unusual cell wall structure surrounding the cell protoplasm; the effects of specific growth regulators; and the anatomic features specially adapted to the control of the uptake of inorganic salts and water and the movement of oxygen and carbon dioxide to and from the atmosphere. Higher plants are autotrophic organisms, obtaining 3 4 /. Biochemical and Photochemical Aspects most of their carbon compounds from atmospheric carbon dioxide; hence the photosynthetic apparatus is of special interest. The photosynthetic cells of higher plants are fairly autonomous and carry out large numbers of biochemical reactions, some of which result in the biosynthesis of unique natural products. Many such substances have still not been identified and many other compounds are known to be present for which nb metabolic role has yet been perceived. In this discussion, I shall consider only those biochemical and physiological aspects of higher plant metabolism that are believed to be closely related to productivity. A. THE CUTICLE AND SURFACE WAXES Certain anatomic features of leaves must first be considered. Examina- tion of the cross section of typical leaf blades (Figs. 1.1, 1.2, 1.3) shows that a waxy layer covers the surface of the cuticle. These waxes, so-called because of their physical rather than their chemical characteristics, were studied intensively by A. C. Chibnall and his colleagues during the period between 1930 and 1950. They were able to isolate and identify many of the substances present by laborious fractional crystallization followed by X- ray analysis. Present-day techniques of separation and identification, espe- cially thin-layer chromatography and gas chromatography, coupled with mass spectrometry, have made the task of identifying the compounds of leaf waxes much easier and more certain. FIG. 1.1. Cross section of a maize leaf showing chloroplasts in the bundle-sheath as well as in the mesophyll (provided by G. Berlyn).
The list of books you might like
