Nitrogen assimilating enzymes and rubisco activity in the seedlings of rice cultivars
2004
Yap, W. S. | Maziah M. | Abdullah M. P. | Abdullah Md. Zain
Nitrogen (N) is a costly and limiting element in plant growth. The processes that govern N fluxes, particularly N uptake and distribution in crops, is of major importance with respect to the environmental concerns and the quality of crop products. Investigation was made to determine the best cultivar that could assimilate both nitrogen and carbon dioxide, effectively. Seedlings of fifteen rice cultivars, Setanjung, Muda, MR 84, RU2242-1-1, IR 64, MR 185, MR 151, MR 159, MR 167, MRQ 34, MR 207, MR 209, MR 211, MR 219 and MR 220 were analyzed for enzymes activity of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH) and ribulose 1,5 bisphosphate carboxylase (Rubisco). NR activity per plant was highest in cultivars MR 159 and MR 167 with 16.80nmol/min and 15.79nmol/min respectively, whereas cultivar MRQ 34 exhibited the highest NiR activity per plant with 10.39nmol/min. Both NR and NiR enzymes are of great importance as they incorporated nitrate into ammonium, which is the first step of nitrogen assimilation in plants. Cultivar Setanjung (0.70µmol/min) showed the highest GS activity per plant followed by MR 151 (0.46µmol/min). GOGAT and GDH activities per plant were highest in cultivars Muda (136.61nmol/min) and MR 167 (l65.92nmol/min) respectively. Rubisco activity per plant was highest in cultivars Setanjung (517.28nmol/min), MRQ 34 (492.20nmol/min) and MR 220 (466.34nmol/min). None of the cultivars above showed an outstanding correlation between N assimilating enzymes and Rubisco activity. Further evaluation was needed to clarify a deeper understanding between the involvements of N assimilating enzymes and carbon metabolizing enzymes.
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