Physicochemical and Environmental Plant Physiology 5th Edition

Book Preface

Let us begin with some comments on the title. “Physiology,” which is the study of the function of cells, organs, and organisms, derives from the Latin physiologia, which in turn comes from the Greek physi- or physio-, a prefix meaning natural, and logos meaning reason or thought. Thus physiology suggests natural science and is now a branch of biology dealing with processes and activities that are characteristic of living things. “Physicochemical” relates to physical and chemical properties, and “Environ-mental” refers to topics such as solar irradiation and wind. “Plant” indicates the main focus of this book, but the approach, equations developed, and appendices apply equally well to animals and other organisms.
We will specifically consider water relations, solute transport, photosynthesis, transpiration, respiration, and environmental interactions. A physiologist endeavors to understand such topics in physical and chemical terms; accurate models can then be constructed and responses to the internal and the external environment can be predicted. Elementary chemistry, physics, and mathematics are used to develop concepts key to understanding biologydthe intent is to provide a rigorous development, not a com-pendium of facts. References provide further details, although in some cases the enun-ciated principles carry the reader to the forefront of current research. Calculations indicate the physiological consequences of the various equations, and problems at the end of chapters provide further such exercises. Solutions to all of the problems are provided, and the appendixes have a large list of values for constants and conversion factors at various temperatures.

Chapters 1 through 3 describe water relations and ion transport for plant cells. In Chapter 1, after discussing the concept of diffusion, we consider the physical barriers to diffusion imposed by cellular and organelle membranes. Another physical barrier associated with plant cells is the cell wall, which limits cell size. In the treatment of the movement of water through cells in response to specific forces presented in Chapter 2, we employ the thermodynamic argument of chemical potential gradients. Chapter 3 considers solute movement into and out of plant cells, leading to an explanation of electrical potential differences across membranes and establishing the formal criteria for distinguishing diffusion from active transport. Based on concepts from irreversible thermodynamics, an important parameter called the reflection coefficient is derived, which permits a precise evaluation of the influence of osmotic pressures on flow.

The next three chapters deal primarily with the interconversion of various forms of energy. In Chapter 4, we consider the properties of light and its absorption. After light is absorbed, its radiant energy usually is rapidly converted to heat. However, the arrangement of photosynthetic pigments and their special molecular structures allow some radiant energy from the sun to be converted by plants into chemical energy. In Chapter 5, we discuss the particular features of chlorophyll and the accessory pigments for photosynthesis that allow this energy conversion. Light energy absorbed by chlo-roplasts leads to the formation of ATP and NADPH. These compounds represent cur-rencies for carrying chemical and electrical (redox potential) energy, respectively. How much energy they actually carry is discussed in Chapter 6.

In the last three chapters, we consider the various forms in which energy and matter enter and leave a plant as it interacts with its environment. The physical quantities involved in an energy budget analysis are presented in Chapter 7 so that the relative importance of the various factors affecting the temperature of leaves or other plant parts can be quantitatively evaluated. The resistances (or their reciprocals, conductances) affecting the movement of both water vapor during transpiration and carbon dioxide during photosynthesis are discussed for leaves in Chapter 8, paying particular attention to the individual parts of the pathway. The movement of water from the soil through the plant to the atmosphere is discussed in Chapter 9 together with new comments on global climate change. Because these and other topics depend on material introduced elsewhere in the book, the text is extensively cross-referenced.
This text is the fifth edition (2020) of Physicochemical and Environmental Plant Physiology (Academic Press/Elsevier, 4th ed., 2009; 3rd ed., 2005; 2nd ed., 1999; 1st ed., 1991), which evolved from Biophysical Plant Physiology and Ecology (Freeman, 1983), Introduction to Biophysical Plant Physiology (Freeman, 1974), and Plant Cell Physiology: A Physicochemical Approach (Freeman, 1970). Thus the series has encompassed 50 years!

This new edition includes recent plant research and over 100 new or updated ref-erences while retaining historically important articles. The text now presents the na-tionalities plus scientific fields of the 115 scientific pioneers specifically mentioned. Summaries are added to each chapter in response to requests by students. But the real inspiration for this new edition is to instill appreciation for the future uses of physics, chemistry, engineering, and mathematics to help understand biology, especially for plants. Physicochemical and Environmental Plant Physiology, 5th ed., thus continues a tradition to emphasize fundamentals plus a quantitative approach suitable for existing situations and habitats as well as for new applications.

Park S. Nobel November 4, 2019