RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE ACTIVITY AND CHLOROPHYLL AND PROTEIN CONTENTS IN 2 CULTIVARS OF FRENCH BEAN-PLANTS UNDER WATER-STRESSAND REWATERING

Two cultivars of bean, Tacarigua and VUL 73-401 were subjected to two levels of water stress followed by rewatering, During the water defici t period, water potential (Psi(W)), osmotic potential (Psi(S)) and rel ative water content (rwc) decreased with an associated decrease of rib ulose-1,5-bisphosphate carboxylase activity (RuBPC), protein and chlor ophyll (Chl) contents. In cv. Tacarigua, the % decrease of RuBPC was l ess marked than that of protein content. There was a significant corre lation among the components of leaf water status and the measured phot osynthetic parameters. Groups of water stressed plants were rewatered, when Psi(W) reached -1.25 to -1.60 MPa. During the recovering period all components of leaf water status increased and reached the control values on the 6(th) day after rewatering. Chl content increased above the control values. Protein content and RuBPC activity also increased during the rewatering period, but the % increases in protein content a nd RuBPCase activity were not parallel.