Effect of Gamma-Amino-Butyric Acid Foliar Application on Physiological Characters of Tomato (cv. Namib) under Salinity Stress

Background and Objectives Salinity and salt accumulation in the soil surface is one of the most important abiotic stresses that limit agricultural crop production in the arid and semi-arid regions of Iran. Thus, finding an alternative production technique or materials to alleviate stress condition is a research priority. One way to decrease the harmful effects of salinity is the foliar application of some chemicals such as Gamma-amino butyric acid (GABA) to increase plant tolerance to salinity. GABA is often accumulated in plants in response to live and non-live stresses such as drought, salinity, oxygen deficit, heat shocks and contamination of pathogens.
Materials and Methods The current study was carried out to monitor the GABA effects on tomato physiological changes under salinity stress. The plants were grown in hydroponic system and received 0 and 50 mM NaCl as control and salinity stress, respectively. GABA at three concentrations 0, 10 and 20 mM was applied as a foliar application in either control or salinity treatments. Physiological characteristics of relative water content (RWC), membrane stability index (MSI), proline, total soluble protein (TSP) and enzymes activity, chlorophyll a, chlorophyll b, total chlorophyll and total soluble carbohydrates (TSC) were measured.
Results The results showed that salinity stress and GABA were effective on the physiological characteristics of tomato. GABA can increase the tolerance of plants to environmental stresses, including salinity stress. MSI, chlorophyll a, total chlorophyll, carotenoids in salinity treatments were lower than control while TSC, proline, peroxidase and SOD increased. RWC, MSI, proline, TSC of GABA treated plant were greater than untreated in either salinity or control conditions. Also, SOD and peroxidase activity elevated in GABA treated plant under salinity stress.
Discussion GABA increased antioxidant capacity in the plant and thus might eliminate radicals and prevents the destruction of cell membrane tissue, including the chloroplast membrane. In general, the results showed that in salinity stress conditions, GABA application as a compatible osmolytes might improve the tomatoes physiological performance and alleviate salinity stress.