Nitrogen Metabolism in Rice Cultivated Under Seasonal Flush of Nitrate

Abstract

Two rice varieties, a land race (Piaui) and an improved variety (IAC-47), were cultivated in pots in a system that simulates the seasonal nitrate flushes in tropical soils. Piaui plants did accumulate more in the shoots than IAC-47, especially in the sheaths. Piaui plants have also shown a low nitrate reductase activity (NRA) at the early stages of growth, what may be and advantage for the accumulation of . Piaui plants showed a higher content and a lower NRA in the flag leaves at anthesis, while IAC-47 on the contrary showed lower content and higher NRA at anthesis. The data indicated that Piaui plants have apparently a higher N-use efficiency than IAC-47 plants do. This ability results in higher content of grain protein, even when growing in poor soils. These results suggest this to be related to a superior capacity of Piaui plants to take up from low nutrient soils, and store it in the reserve pools during the early stages of growth and development.