Photosynthetic studies with mesophyll protoplasts from Notonia grandiflora, a crassulacean acid metabolism plant

Abstract

AbstractA method is described for rapid enzymatic isolation of mesophyll protoplasts and cells from the crassulacean acid metabolism (CAM) plant Notonia grandiflora DC. The mesophyll protoplasts exhibited high rates of 14CO2 fixation both in the light (45 μmol of CO2 fixed mg−1 Chl h−1) and in the dark (20 μmol of CO2 fixed mg−1 Chl h−1). The protoplasts also showed O2 evolution (40 μmol of O2 evolved mg−1 Chl h−1) without added bicarbonate. Exogenously added bicarbonate had no stimulating effect on the O2 evolution. Analyses of early photosynthetic products in the light showed the formation of both C3 and C4 acids. Aspartate was found to be a predominant photosynthate.