Papel da glutamina na regulação do influxo de nitrato em raízes de feijão-caupí expostas à salinidade

Abstract

There are many studies showing that the salinity may directly affect the nitrate uptake, from their osmotic effect, nature of the salt and its ionic composition. However, little is known about the mechanisms related to the salt ability to inhibit the nitrate acquisition indirectly. This study was carried with aim to induce inhibition of NO3- influx in cowpea roots of indirect form triggered by a negative feedback mechanism, caused by the increase in the pool of free amino acids in the tissue, induced by salt stress.For this, were done three isolated studies and continuous.The exogenous glutamine application promoted an increase in the free amino acids content.The presence of glutamine decreased significantly the nitrate acquisition.The free ammonium can also be listed as a key-compound in the role of nitrate influx regulation, since use of the MSX (Methionine sulfoximine) promoted the increase of NH4+ content and also reduced nitrate influx, but, in a lesser degree when compared to treatment with AZA (Azaserine). Salt stress caused a reduction in NO3- influx by decrease in the growth of plants induced by salt. The data indicated which this reduction in the influx is triggered by increase of amino acids content, mainly the glutamine, that is main likely compound to act as signal in the N-feedback regulation.