Nitrate Assimilation and Crassulacean Acid Metabolism in Leaves of Kalanchoë fedtschenkoi Variety Marginata

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Abstract
The enzymes necessary to assimilate NH3 either via glutamine synthetase and glutamate synthase or via the glutamate dehydrogenase pathways are present in both green and white leaf tissues of K. fedtschenkoi. Nitrate reductase activity develops to a maximum in a crassulacean acid metabolism (CAM) plant canopy before either ribulose 1,5-bisphosphate carboxylase, or phosphoenolpyruvate carboxylase, or CAM. Nitrate reductase also is activated each morning and is inactivated late in the day as in other plants. Apparently, there is no direct relationship between nitrate reductase activity and the level of acid, its daily pattern or the amplitude of CAM. Though nitrate reductase is activated maximally each day by light, in Kalanchoe leaves for 6 days the activity followed a precise daily pattern independent of continuous light or dark.