Abstract:  Taking the medium culture leek as experimental material， we studied the effect of spraying different concentrations of gamma aminobutyric acid （GABA） on growth and inorganic nitrogen metabolism of leek under the condition of high nitrogen. The results showed that， the stem height， stem diameter， leaf width， fresh and dry weight of leek were higher in the treatments of 25-100 mmol·L-1 GABA than the control after 6 d， in which 75 mmol·L-1 GABA treatment was the most effective. Compared with the control， the content of nitrate nitrogen and nitrite nitrogen reduced in the treatments of 25-75 mmol·L-1 GABA during 0-12 days after spraying， while the ammonium nitrogen content and the activity of nitrate reductase （NR）， nitrite reductase （NiR）， glutamic decarboxylase （GAD） increased. The effect of 75 mmol·L-1 GABA treatment was better than the other treatments， which got the most obvious effects on the 6th day. It indicated that GABA sprayed on the leaves of leek could be absorbed， which caused the decrease in nitrate content of leek by inducing the key enzyme activity of NR， NiR and other in inorganic nitrogen metabolism， and finally improved the yield and quality of leek.

Key words: GABA, leek, growth, nitrate