Changes in Adenylate Nucleotide Levels in the Leaves of Capsicum annuum During Water Stress

Abstract

Summary Young Capsicum annuum plants were subjected to a water stress cycle which reduced dawn leaf water potential from a control value of -0.25MPa to between -0.55 and -0.65MPa. Initially leaf osmotic potential also decreased, so that leaf turgor was maintained. After 4-5 days without water osmotic adjustment largely ceased and leaf turgor was then reduced. Extremely small changes in leaf water potential (0.1-0.2MPa) resulted in significant reductions in leaf A TP content to 70-80% of the control level. This was not a result of impaired photosynthesis; leaf carbon dioxide gas exchange was maintained at the control rate and the photochemical reactions of isolated chloroplasts were unaffected. Rather it reflected a general loss of adenylate nucleotides, and the leaf energy charge ratio was maintained throughout the period of water stress.