Integration of Biochemical Processes in the Physiology of Water Stressed Plants

Abstract

Crop productivity under water stress is determined by the way in which biochemical processes are integrated and change in relation to the environment. In the field, productivity is determined by the responses of the plant at the morphological or physiological process level of organisation e.g. leaf area or net photosynthesis. Their relative importance in determining crop growth is briefly considered. The manner in which stress affects photosynthesis, photorespiration and energy utilisation in the leaf and cell and the basic lesions to metabolism are outlined. ATP synthesis by photophosphorylation is inhibited whilst electron transport and reductant supply are relatively insensitive. Inbalance in these processes causes changes in secondary carbon and nitrogen metabolism involving amino acid and quaternary ammonium compounds and phospholipid synthesis; terpenoid metabolism may also be linked. Aspects of these in relation to carbon and nitrogen fluxes and cellular energetics are considered together with possible controls. Stress induced changes in metabolism of glycophytes are discussed in relation to the concepts of directed metabolism with useful biological control function, or to undirected metabolism, resulting from stress, without important control function.