Effects of Salicylic Acid on Gaba Metabolism in Pepper Plants under Stress Conditions

Abstract

Salicylic acid (SA) is a potential plant hormone that enhances the capacity of plants to cope with various stress factors. Gamma-aminobutyric acid (GABA) is an important non-protein amino acid, which is increased by stress conditions. However, the interaction between SA and GABA is not well known. In this response the aim of this study was to evaluate the effects of SA on GABA metabolism in pepper plants (Capsicum annuum L.) under individual and combined salt (NaCl) and polyethylene glycol (PEG) induced osmotic stresses. Total chlorophyll content, the activities of glutamate dehydrogenase (GDH, EC 1.4.1.4) and glutamate decarboxylase (GAD, EC 4.1.1.15), GABA content were analyzed in the leaves of pepper plants. Total chlorophyll content was decreased by combined salt and PEG-induced osmotic stresses. Individual SA, NaCl and PEG applications increased GDH activity. Under stress conditions, SA did not enhance GDH activity; however, GAD activity was increased within these conditions. Our results showed that salicylic acid application did not enhance GABA accumulation during individual and combined stress conditions. The dose and application process of SA could lead to this result. However further studies should be done to identify the interaction between SA and GABA under various stress conditions.