Physiology of Crop Yield, Second Edition. Robert Hay and John Porter. 2006. Wiley-Blackwell Publishing, Oxford. 314 pages. $84.99. Paperback. ISBN: 978-14051-0859-1. Print-on-Demand.
Robert Hay is Visiting Professor at the Swedish University of Agricultural Sciences, Uppsala, and John Porter is Professor of Agroecology at the Royal Veterinary and Agricultural University in Denmark. This book was published in 1989 with the title of An Introduction to the Physiology of Crop Yield. The second edition preserves the topics of analysis of yield in the first book and updates the first publication with information of phenology, crop modeling, and sustainable crop production. The new book has 10 chapters of text with numerous line drawings and tables and over 30 pages of references. The book is aimed at the advanced undergraduate student and other readers with substantial knowledge of plant anatomy, biochemistry, and plant physiology. The book does not address the biochemistry of plant processes but rather considers how plant development and the environment affect these processes and the resultant crop yields.
The introductory chapter summarizes the contents of the book and introduces core topics of total and intercepted solar radiation, the conversion of radiant energy into chemical energy, and the partitioning of dry matter in relation to crop production. This chapter references other chapters in the text in which more detailed discussions and models are presented. The second chapter is “Development and phenology” and covers interactions between development and environment on resulting events that make it possible for crops to be cultivated in diverse geographic areas that are outside their centers of origin. A series of examples illustrates crop development in species of varying complexities in response to resources and changes in the environment.
The third chapter addresses “Interception of solar radiation by the canopy.” Readers learn about physiology of leaf production, expansion, and lifespan and stem branching in the development of the crop canopy for the interception of solar radiation. The fourth chapter deals with “Photosynthesis and photorespiration” and describes how crops convert intercepted solar energy into chemical energy by photosynthesis, thereby allowing plants to concentrate the carbon of the air more than 40-fold into carbohydrates. Efficiency of conversion of solar energy is discussed at scales of plant cells, leaves, and canopies. Readers learn about energy of light, dimensions of cells and leaves, nitrogen nutrition and photosynthesis, and C3 and C4 mechanisms of photosynthesis. Chapter 5 deals with the respiratory loss of carbon dioxide from crops and how this loss affects crop productivity. The text deals with mitochondrial respiration, thereby distinguishing the process from photorespiration. The importance of mitochondrial respiration in providing energy for plant growth and for maintenance activities such as nutrient acquisition and other functional process in plants is presented. The efficiencies of conversion of glucose into various chemical compounds such as complex carbohydrates, lipids, and proteins are discussed and compared among plants and yield components of different composition, including corn, wheat, and soybean. Partitioning of daily assimilation of carbon (called assimilate) into growth and maintenance respiration is considered for crops in the field.
Chapter 6 deals with “The partitioning of dry matter into harvested organs.” This chapter is one of the most extensive ones in the book with regards to page length. The partitioning of total dry matter into harvested parts is called the harvest index. The ontogeny of leaf and plant development partitioning of assimilate between sources and sinks is discussed along with the competition of grains, tubers, tillers, or other harvested parts for resources. Time courses, yield limitations, and crop improvement and management are factors considered in the presentations of partitioning of assimilate in crops.
Chapter 7 addresses “Limiting factors and the achievement of high yield.” This text notes that solar radiation is the primary limiting factor considered in preceding chapters. Water and nitrogen receive attention in this chapter. Acquisition and efficiency of use of these factors and how these factors affect crop development are discussed. Crop yields are reviewed under conditions in which these factors are limited.
Chapter 8 considers “Physiology of crop quality.” Previous chapters dealt with dry matter production and harvested products in relation to environment and management. This chapter deals with how physiologists can assist in the breeding and selection of crops that have superior quality as well as dry matter yield. Quality was defined as relating to the quantity of a major component (protein, oil, starch), composition (lysine, triglycerides, vitamins, mineral elements), cooking and processing properties, size and appearance of produce, diseases and blemishes, and taste and texture of foods. The text addressed the fact that high quality and high yields are not necessarily inversely related. The presentation concentrated on protein in wheat, oil and protein in soybeans, glucosinolates and erucic acid in oilseed rape, tuber size and processing quality of potatoes, and quality of forages. The authors noted that the physiology of quality of horticultural crops was a rich field for investigation but was beyond the scope of the book.
Chapter 9 addresses “The simulation modeling of crops.” The value and complexity of developing predictive models of the effects of the environment on crop physiology are discussed. Building of crop models to understand how crops respond to the environment and to predict crop behavior under new conditions in the environment is discussed. Working models for wheat, corn, and soybean are examined in detail.
The last chapter discusses the future of crop physiology. The authors note that the heyday of crop physiology occurred between 1960 and 1990 and that the physiological focus on whole plants has been superseded by molecular biology and genetics. The authors state that although modern molecular biologists may believe that presence or expression of a gene means that crop yield and quality will be affected, it should be recognized that the emerging generations of crop scientists must operate at molecular and whole-plant levels. The text concentrates on how crop physiologists can play roles in four areas—the consequences of lowering inputs to improve efficiency of use of nutrients and other resources; the effects of climate change and variability on crop yields; the nutritional, technological, and environmental quality of products; and the development of crops for non-food products such as biomass energy and biopolymers.
The extensive list of references cited will be of interest to all crop physiologists. This book will be a valuable tool for teachers, researchers, and advanced undergraduate and postgraduate students of agricultural sciences, environmental sciences, and ecology and will give these individuals a good whole-plant understanding of growth, development, and yields. A lot of the emphasis in the book is on major agronomic crops, but the information presented is basic and can be applied to horticultural crops equally well.