Amin Abbasi

In order to investigate the effect of foliar spraying of γ_aminobutyric acid in different concentrations on enzymatic antioxidant change in the thymus daenensis Celak under water deficit stress, this research was carried out as factorial experiment conducted based on a randomized complete block desing with three replication in the research greenhouse of the Department of Plant Production and Geneteics of Maraghe University. The main factor included levels of water stress (30%, 60%, 90% field capacity) and sub factors included no spraying of GABA, 25 mM GABA, 50 mM GABA and 75 mM GABA. According to the results the amount of Catalas and Hydrogen peroxide effected by the intraction of water stress × foliar spraying. The result of mean comparison show that with increasing in stress intensity, the activity of Catalas first increased and then at high stress intensity (30 % FC) decreased. Also the highest amount of Catalas was obtained from the 25 mM GABA at 60 % FC. The amount of Hydrogen peroxide was increased with increasing stress intensity. Also its amount was decreased with GABA spraying. So the use of GABA at 30 % FC caused by 24 % decrease in Hydrogen peroxide compare to the no spraying of GABA. The lowest Hydrogen peroxide was obtained from the 25 mM GABA at 90% FC.