摘要：Present study was conducted to investigate and characterize the effect of nitrate and Gln (glutamine) on the trend and rate of nitrate uptake by HATS (High-affinity transport system) in Nicotiana plumbaginifolia plant under hydroponic system using ion depletion technique. The plants were grown at 16 h light/8h dark at 24/20 °C, 70% humidity, 150 μmol m-2 sec-1 light intensity and on the commercial soil with NPK fertilizer. About 28-day plants were transferred to hydroponic media containing complete nutrition solution with 0.5 mM NO3- at the same growth conditions for 1 week. To better understanding of time-course of HATS induction, starved plants of nitrogen for 7 days were supplied with 5 different concentrations including 10, 50, 75, 100 and 150 μM NO3-. Monitoring of trend of NO3- absorption showed that at least 2 h is adequate to induce HATS activity at 150 μM NO3-. A surprising finding was that transfer N-starved plants to media containing high concentration of NO3- (10 mM) for 48 h resulted in increasing the rate of NO3- uptake by HATS. Amino acid Gln applied to N-deprived plants either as pretreatment or with NO3- significantly inhibited nitrate uptake by HATS compared to control conditions. The results collectively indicate that high-affinity nitrate transport is regulated by nitrate itself and the metabolites of its assimilation such as amino acid s.
