Nitrate reductase activity (NRA) and different levels of nitrogen in sweet potato (Ipomoea batatas (L.) Lam)
1985
Batanes, J.L.
In general NRA increased with increasing levels of N. The activity of the enzyme was highest at 30 DAP (1.55 u mole NO2 dm -2hr-1) and decreased with plant age up to harvest. Maximum activity (1.82 u mole NO2-dm-2hr-1) was observed at the highest level of fertilizer application (220-150-150 kg NPK per ha). High N fertilization stimulated vegetative growth and varieties that have vigorous tended to have higher NRA. NRA was found to be correlated with total DM (dry matter), LAI (leaf area index), NRA (nitrates reductase activity) and CGR (crop growth rate) at a certain stage of plant growth and development. NRA differed significantly among varieties and was poorly correlated with tuber yield. Tres-colores was observed to have the highest enzyme activity at 30 DAP (2.02 u mole NO2-dm-2hr-1) but gave the lowest total tuber yield (13.99 t/ha) at harvest. BNAS-57 gave the highest total tuber yield (44.23 t/ha) at fertilization rate of 50-150-150 kg NPK per ha and had relatively lower NRA (0.67 NO2-dm-2hr-1) throught the growing period. Although NRA could not be used directly as a selection criterion for identifying high yielding varieties, it can lead to the identification of vigorous lines which may possess good tuber yield potential due to the significant correlation of NRA with total DM production at 60 DAP
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