Glutamate dehydrogenase activity, protein and total nitrogen content in seedlings of maize at varying growth temperatures

Seedlings of Zea mays L. cv. Ganga Safed-2 were raised with 1/2 strength Hoagland 's solution containing 5 mM NH4NO3 as sole nitrogen source at 12 h photoperiod (70 Wm(-2)) and at varying temperature of 10-40 degrees C, to examine the effect of temperature on l-glutamate dehydrogenase activity nitrogen status of roots and shoots and growth of roots and shoots. Total NADH-glutamate dehydrogenase activity in both roots and shoots increased with the increase in temperature up to 30 degrees C and then it declined sharply during a temperature range between 30-40 degrees C. The protein and Kjeldahl nitrogen contents of the shoots also showed almost a similar trend. However, the root protein content remained almost unchanged at a temperature range between 15-30 degrees C and declined slightly at higher temperature. The optimum temperature for maximum Kjeldahl nitrogen content in the roots was 25 degrees C whereas that for the shoots was 35 degrees C, although the growth of the either organ, as measured by their fresh or dry weights increased up to 40 degrees C. The in vitro stability of NADH-GDH from root tissue was fairly high up to 5 h a low temperature (5-20 degrees C) whereas the same from the shoot tissue was stable significantly up to 10 degrees C only. A phase separation temperature was observed in in vitro stability of both, root-as well as shoot-enzyme. The experiment however, demonstrated some differences in the NADH-GDH activity and nitrogen productivity of root and shoots tissues at different growth temperatures and indicates a possible involvement of this enzyme in ammonia assimilation in the plants growing at a wide temperature range.