ABSTRACT
The role of water in the overall growth processes and productivity of plants has received considerable attention in recent years. Much research has been aimed at expanding our knowledge of how plants respond to their environment, particularly how they adapt to changes in the environment in order to maintain a water balance favorable to growth and development. This chapter provides a brief account of how plant water stress develops and the importance of stress relationships to the overall effort of modeling crop growth. It discusses the effects of plant water stress on photosynthesis with particular emphasis on stomatal activity and the adaptive stomatal processes that control CO2 exchange. Plant water stress relationships form the basis for an understanding of many crop growth and development responses, and thus are vitally important to all phases of crop productivity. These relationships, however, are generally lacking or at best are treated superficially in many crop growth models.
