Determination of the effects of exogenous GABA application on some biochemical parameters in tomato plants under peg-induced osmotic stress

Tomato (Solanum lycopersicum L.) is one of the most economically important plant grown worldwide, mostly in warm regions. However, plants in these areas are exposed to osmostic stress because of the climate and salty environments. Gamma aminobutyric acid (GABA) plays a significant role in plant metabolism especially under stress conditions. In this study, we analyzed the effects of exogenous GABA on plant defence mechanism. PEG-induced osmotic stress was applied to tomato plants. After the harvest, the contents of phenolic substances, GABA, MDA, total chlorophyll and the activities of antioxidant enzymes were analyzed. Exogenous GABA treatment increased total chlorophyll content and caused a decrease in MDA content. GABA treatment caused a significant increase in gallic acid and chlorogenic acid contents. PEG and GABA applications induced CAT and GR activities. According to our results, we can conclude that exogenous GABA treatment can have positive effects under normal conditions and PEG-induced osmotic stress by stimulating some phenolic substances and antioxidant enzyme activities and endogenous GABA content. Keywords : Antioxidant enzymes, Drought, Gamma-aminobutyric acid, HPLC, Phenolic content, Solanum lycopersicum.