Nitrate Assimilation in Rice Grown under Lowland Conditions

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Abstract
Pattern and extent to which the main shoot of rice (Oryza sativa L.) cv. Pusa 33 assimilates NO3‐ when grown under lowland conditions was determined in a field study. The in vivo NR (nitrate reductase) activity is low as compared to the value in other cereals grown under aerobic soil conditions. The leaf blades had higher NR activity (g fr. wt.)‐1 than the sheaths and stem. Calculation of total NO3‐ (mol) reduced in the main shoot, obtained by integrating the in vivo NR assay values per plant part and per day over the duration for which the various plant parts on the main shoot remained metabolically active, showed that out of the total reduced N at harvest, 16.6% was assimilated via the enzyme nitrate reductase. In the leaf sheaths and stem the NO3‐ was reduced to slightly over 50% of the total NO3‐ that was reduced in the main shoot. The rest of the amount was reduced in the leaf blades.