The eefects of exogenous melatonin on some physiological parameters in tomato plants under salt stress

Melatonin (N-acetyl-5-methoxytryptamine) is a low molecular weight substance found in several organisms. However, the effects of melatonin on plant metabolism are of special interest. Tomato (Solanum lycopersicon L.) has an important economic value in our country and worldwide among agricultural products. In this study the effects of exogenous melatonin on some physiological parameters were investigated in tomato plants under salt stress. Tomato plants were grown in a growth chamber under controlled conditions. Melatonin solution (200 µM) was sprayed to the tomato leaves and then salt stress (100 mM NaCl, 200 mM NaCl) was applied to the pots in Hoagland solution. In this study the contents of gamma-aminobutyric acid (GABA), which has a signal role under stress conditions, and phenolic substances, which have antioxidant effects, were analyzed from tomato plant leaves via HPLC and total chlorophyll and the indicator of cell damage malondialdehyde (MDA) content analyses were determined via spectrophotometer. Exogenous melatonin treatment increased total chlorophyll content, GABA content and some phenolic substances; however, MDA content was reduced under melatonin application. Therefore, we can suggest that exogenously applied melatonin could have alleviative effects in tomato plant under salt stress.