Stable Isotopes and Plant Carbon-Water Relations

Bernard Saugier

• Publisher: Academic Press
• Year: 2012
• eBook ISBN: 9780080918013
• Topic: Sciences biologiques
• Subtopic: Botanique

This 33-chapter volume presents a critical examination of the importance of stable isotopes in understanding key plant metabolic processes. - Carbon isotope analyses for estimates of plant water use and metabolism - Integrated estimates of stress impacts and life history in ecological systems - Hydrogen and oxygen isotope analyses for evaluating water sources and transpiration - Use of stable isotopes in scaling from leaf to global levels - Sections include: History and Theoretical Considerations, Ecological Aspects of Carbon Isotope Variation, Agricultural Aspects of Carbon Isotope Variation, Genetics and Isotopic Variation, Water Relations and Isotopic Composition

Part I

History and Theoretical Considerations

Introduction to History and Theoretical Considerations

The contributions to this section focus on the fundamentals of plant carbon–water relations, the historical development of stable isotopes in plant biology, and the biochemical basis of fractionation of stable isotopes of carbon, hydrogen, and oxygen. The introductory chapter sets the stage with a summary of basic aspects of gas exchange as they relate to carbon dioxide and water vapor fluxes between plants and the atmosphere and also establishes a common set of terms relating water loss and carbon gain. That chapter is followed by a historical view of stable isotopes in plants by Ehleringer and Vogel, who point out that the initial basic observations on this topic are all derived from geochemistry. O’Leary follows with a discussion of the basic isotope fractionation processes and establishes the linkages between carbon isotopes and plant gas exchange. In the subsequent chapter, Farquhar and Lloyd derive a theory linking plant gas exchange and atmospheric gas composition, illustrating that both carbon and oxygen isotopes in carbon dioxide provide insightful information that can be used to understand physiological processes at the leaf level and then can be used to scale for global considerations. In the last chapter of this section, Flanagan discusses the theory behind how both hydrogen and oxygen stable isotope analyses of leaf water reveal information on biological and atmospheric processes.

1

Introduction: Water Use in Relation to Productivity

Publisher Summary

This chapter discusses the concept of water loss with respect to photosynthesis and provides a set of terms relating to plant-water use. There could be significant differences among cultivars of a crop in water consumption requirements in relation to biomass production. These observations show that atmospheric conditions are of importance in determining absolute relations between water consumption and biomass productivity of a crop. Instantaneous water-use efficiency is defined as the ratio of the fluxes of net photosynthesis (A) and transpiration (E). The advantage of intrinsic water-use efficiency allows direct comparison of intrinsic physiological considerations, factoring out the confounding effects of temperature and humidity gradient differences between plants. While instantaneous and intrinsic water-use efficiencies might be useful in evaluating water and carbon exchange on a short-term basis, they do not necessarily scale to long-term considerations, such as might be of interest to those studying canopy productivity or growth.

I. Introduction

Water loss with respect to photosynthesis has been the topic of numerous books and reviews and has attracted widespread interest from diverse groups, ranging from those interested in basic mechanistic aspects of plant physiology to those concerned with constraints on agricultural production (Fischer and Turner, 1978; Taylor et al., 1983; Sinclair et al., 1984; Stanhill, 1986; Turner, 1986). The intent of this section is to briefly introduce the roots of this interest and to provide a set of terms relating to plant-water use that will be useful when reading the remaining chapters in this volume.

II. A Long-Standing Interest in Water–Use Efficiency

For over a century there has been interest in understanding the relationships between water consumption by plants and overall productivity. Ecologists have been interested in how leaves of different species varied in these parameters, especially in response to seasonal and geographical changes in moisture availability and how these responses influenced both structural and physiological features of natural vegetation. This interest was pioneered by natural scientists and plant geographers (Haberlandt, 1884; Schimper, 1898; Warming, 1909) and later with an ecological emphasis (Livingston and Shreve, 1921). At the same time, agronomists, whose primary goal was increasing productivity, were especially interested in the water requirements for growth of a broad range of crop species (Briggs and Shantz, 1913b).

The pioneering experiments in this area involved growing plants in pots and other containers, where precise (but very time-consuming) information was gained by measuring plant growth and water loss over extended time periods (Briggs and Shantz, 1913a; Shantz and Piemiesel, 1927). From these studies of crop and native plants, it became clear that there was substantial variation in the relationships between water consumption and biomass production. While the mechanistic bases were unknown at the time, plants could be separated into two distinct groups on the basis of their water requirements for growth. We now know that these two groupings represent the C₃ and C₄ photosynthetic pathways. Furthermore, these early studies established that there could be significant differences among cultivars of a crop in water consumption requirements in relation to biomass production.

These observations showed that atmospheric conditions were of overriding importance in determining absolute relations between water consumption and biomass productivity of a crop. The large site-to-site and year-to-year variations in absolute water consumption characteristics (driven by temperature and humidity conditions) of the same crop were confoundin...

Table of contents

• Cover image
• Title page
• Table of Contents
• Physiological Ecology: A Series of Monographs, Texts, and Treatises
• Copyright
• Contributors
• Preface
• Part I: History and Theoretical Considerations
• Part II: Ecological Aspects of Carbon Isotope Variation
• Part III: Agricultural Aspects of Carbon Isotope Variation
• Part IV: Genetics and Isotopic Variation
• Part V: Water Relations and Isotopic Composition
• Index