Progress in environmental plant physiology, as in other scientific disciplines, involves repeated cycles of observation or experimentation followed by data analysis and the construction and refining of hypotheses concerning the behaviour of the plant-environment system. This process is illustrated in very simplified form in Figure 1.1. At any stage the information and hypotheses may be qualitative or quantitative, and there may be more or less emphasis on the use of controlled experiments for providing the necessary data.

The initial stages of an investigation tend to provide a more qualitative description of system behaviour: much early ecological research, for example, was concerned with the description and classification of vegetation types, with a relatively small proportion of effort being devoted to understanding the underlying processes determining plant distribution. Further improvements in the understanding of any system, however, require a more quantitative approach based on a knowledge of the underlying mechanisms.

It is at this second level that this book is aimed: I have attempted to provide an introduction to environmental biophysics and to the physiology of plant responses that can be used to provide a quantitative basis for the study of ecological and agricultural problems. Further information on specific topics may be found in specialised texts referred to throughout the book.