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Articles

Nitrate Assimilation and Crassulacean Acid Metabolism in Leaves of Kalanchoë fedtschenkoi Variety Marginata ¹

H. Max Vines

Clanton C. Black, Jr.

Biology Department, Seoul Natinal University, Seoul 151, Korea, Horticulture Department, University of Georgia, Athens, Georgia 30602, Biochemistry Department, University of Georgia, Athens, Georgia 30602

The enzymes necessary to assimilate ammonia either via glutamine synthetase and glutamate synthase or via the glutamate dehydrogenase pathways are present in both green and white leaf tissues of Kalanchoë 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. However, there does not appear to be any 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 Kalanchoë leaves for six days the activity followed a precise daily pattern independent of continuous light or dark.

¹ This research was supported partly by NSF grant PCM77-08548 and the Mobil Foundation.