EFFECT OF NITROGEN NUTRITION ON NITRATE AND NITRITE REDUCTASE, GLUTAMINE-SYNTHETASE, GLUTAMATE SYNTHASE AND GLUTAMATE-DEHYDROGENASE IN THE CAM PLANT KALANCHOE-LATERITIA ENGL

The activity of the enzymes involved in nitrogen metabolism NR, NiR, GS, GOGAT and GDH was studied in the CAM Kalanchoe lateritia using nitrogen starved plants later grown under three different nitrogen nutritional conditions (N, N/5, N/10 plant groups). After 1 day of the nitrogen resupply the NR activity increased similarly in all groups; the rise was higher after 7 days and significantly different from one group to the other. After 1 day the NiR activity increased in all plants with close values in N and N/5 and the lowest one in the N/10 group and with ongoing treatment an increase of activity was only observed in N plants. GS and Fd-GOGAT behaved similarly to each other, their activities increase with nitrogen increase; the NADH-GOGAT behaved in the opposite way and moreover its activity fluctuates along the day. NADH- and NADPH-GDH also fluctuate however the maximum activity found for the former isoenzyme was not affected by nitrogen level whereas the activity of the latter was lowest in N/10 plants. The data showed that in this CAM plant the activity of all enzymes was affected by nitrogen nutrition with exception of the mitochondrial NADH-GDH.