PARTIAL DECLINE OF ARACHIS-HYPOGAEA L PHOTOSYNTHESIS TRIGGERED BY DROUGHT STRESS

Photosynthetic capacity (PC) of three peanut cultivars (Arachis hypoga ea L. cvs, 57-422, 73-30, and GC 8-35) decreased during drought stress (decline in relative water content from ca. 95 to 70 %) and recovered two days after rewatering, Mild water stress was not limiting for the total ribulose-1,5-bisphosphate carboxylase/oxygenase activity, since this enzyme activity increased under drought, Photosystem (PS) 2 and PS1 (the latter only in cv. GC 8-35) electron transport activities dec reased under drought, The ratio of the variable to maximal chlorophyll fluorescence (F-v/F-m decreased mainly in the cv. GC 8-35, All cultiv ars showed decreases in photochemical quenching (q(p)) and quantum yie ld of PS2 electron transport (phi(e)). Increase of basal fluorescence (F-0) was observed in the cvs, 73-30 and GC 8-35, while the cv. 57-422 showed a decrease. After rewatering a sharp increase was observed in the majority of the parameters. Thus under the present stress conditio ns, the cv. GC 8-35 was the most affected for all the parameters under study. The cv. 57-422 showed a higher degree of tolerance being gradu ally affected in photosynthetic capacity (PC) in contrast to the two o ther cvs. which showed a sharp decrease in PC at the beginning of the drought cycle.