Effects of Seasonal Nitrate Flush on Nitrogen Metabolism and Soluble Fractions Accumulation in Two Rice Varieties

Abstract

ABSTRACT Two rice varieties, ‘Piaui’ (a landrace) and ‘IAC-47’ (an improved variety), were grown in nutrient solution containing 20 mg nitrate (NO3 −)-nitrogen (N) L− 1 up to 32 days after germination (DAG). After this, a group of plants received 200 mg NO3 −NL− 1, while the other was kept at 20 mg NO3 −NL− 1 up to 42 DAG. From 42 until 56 DAG, all plants received 5 mg NO3 −NL− 1. Plants were collected at 42 and 56 DAG, soluble fractions, nitrate reductase (NR) and GS enzymatic activities were determined. The nutritional history of the plants affected significantly the uptake and use of nitrogen (N), and should be taken into consideration in the studies of N-use efficiency. The variety ‘Piaui’ was more efficient than ‘IAC-47’ in N-uptake use, accumulating more NO3 − in its tissues at the initial phases of its cycle for subsequent utilization.