Metabolic Effects of Water and Salinity Stress in Relation to Expansion of the Leaf Surface

Abstract

Leaf expansion is comparatively sensitive to the onset of stress, and metabolic dysfunctions purported to contribute to the leaf expansion response can be judged against this sensitivity. Accumulated evidence does not support the proposition that leaf expansion is controlled primarily by the availability of basic metabolites during exposure to stress, nor is there evidence for the primacy of any specific metabolic lesion. Caution must be exercised in reaching such conclusions, however, as there is difficulty in separating cause and effect in the relationships between tissue physical status (water or salt), metabolic function and expansion. Certain metabolic consequences of stress, particularly those leading to the accumulation of specific organic solutes, are viewed as adaptive. Such responses must be viewed in the light of their metabolic cost and the possibility that they contribute more to survival than to continued growth and expansion. Recent information on the effects of water and salinity stress on plant metabolism is reviewed in this paper with respect to these various considerations.