Two rice cultivars, Piaui (a landrace) and IAC-47 (an improved variety), were grown in nutrient solution containing 20 mg nitrate (N-NO3-) L-1 up to 32 days after germination (DAG). After this, a group of plants received 200 mg N-NO3- L-1, while the other was kept at 20 mg N-NO3- L-1 up to 42 DAG. From 42 until 56 DAG, all plants received 5 mg N-NO3- L-1 until the end of the cycle. These treatments were applied with the objective to simulate nitrate flush in tropical regions. Plants were collected at 133 DAG and separated in to leaf flag, leaf 2, stem and roots. N contents in amino acids, nitrate and ammonium forms, soluble sugars, nitrate reductase (NR) and glutamine synthetase (GS) enzymatic activities were determined. The evaluated varieties replay in different manner about accumulate and translocation nitrate. The variety Piaui seems to accumulate more NO3- in the tissues at the initial phases of its cycle, allowing subsequent remobilization. Flag leaf and leaf 2 seem to act as preferential sites of N accumulation, being this accumulation more intense in the landrace variety.
amino-N; nitrogen assimilation enzymes; nitrate uptake; Oryza sativa L.; soluble sugars; traditional varieties
