Determination of the effects of gibberellic acid on gaba and antioxidant defence system in Phaseolus vulgaris L. (bean) plants exposed to salt and drought stresses

Drought and salinity are important environmental stress factors which reduce the plant productivity all around the world. Therefore, understanding the mechanisms of crop plants against abiotic stress conditions is very important to increase the productivity. However, the defence mechanisms of plants against multiple abiotic stress conditions and the the relation between GABA metabolism are still unknown. In this study, the effects of gibberellic acid (GA) on RWC, chlorophyll content, antioxidant defence system, malondialdehyde (MDA) and GABA contents were investigated in Phaseolus vulgaris L. plants exposed to salinity, drought and combined stress conditions. In salt and drought stress conditions, GA had positive impact on RWC, however GA did not cause significant changes in total chlorophyll content. In GA applications, it was observed that CAT and GR activities were decreased compared to the control plants, however significant differences were not found in SOD and APX activities. GABA was increased by high salt concentration, however GA application did not cause any significant changes in GABA content. GA application decreased MDA content in salt and drought stress conditions. According to the data obtained from this study, in multiple stress conditons, GA had effects on defence mechanism in bean plants, but GA did not cause any significant changes in GABA metabolism. Therefore, it is thought that studying the relationship between different plant hormones and GABA in stress conditions, could clarify GABA metabolism particularly.