Drought-induced enhancement of protease activity during monocarpic senescence in wheat

The effect of water stress on flag leaf senescence and protease activity during grain development was examined in a wheat variety. Total chlorophyll content and soluble protein content were used as markers for monocarpic senescence. Endopeptidase activities and exopeptidase activities were assayed using ribulose-l,5-bisphosphatecarboxylase (RuBisCo) as a physiological substrate at acidic (pH 4.8), neutral (pH 7.0) and alkaline (pH: 8.5) values at three stages during grain-filling period. Water stress enhanced the rate of monocarpic senescence and concomitantly increased the endopeptidase and exopeptidase activities at all pHs tested in the leaves. The above observations showed that different proteolytic enzymes may come into play under water stress which are independent of the reproductive sink effect.