To evaluate the effects and initial-action mechanism of salinity on NO-3 reduction and N compounds accumulation, 42-day-old Anacardium occidentale (CCP-1001) plants were hydroponically grown in 100 mmol L-1 NaCl for 8 days (short-term experiment), in greenhouse. The results show that reduction in transpiration rates due to salinity had a relevant role in the regulation of NO-3 reductase (NR) activity, which decreased considerably in leaf. On the contrary, glutamine sintetase (GS) activity increased in leaf due to salinity. The increase in activity of GS in leaf was followed by the soluble amino acids concentration, in particular proline, and by the total soluble proteins content as well. On the other hand, increase in concentration of organic N fractions in leaf was concomitant to decrease in total chlorophyll content and increase in concentration of NH+4 . It is most likely that the increase in GS activity of cashew leaf may be due to additional supply of NH+4 and glutamate coming from catabolism of amino acids and proteins and from increase in photorespiratory activity.
salinity stress; compatible solutes; N assimilation
