Determination of the effects of melatonin on tomato under boron stress in terms of certain physiological and molecular parameters

Biotic and abiotic stress factors cause significant economic damage to tomato cultivation every year. Melatonin is a tryptophan-derived plant growth regulator whose presence in plants has been discovered. Studies conducted on a wide range of plants have revealed many links between the presence of melatonin and plant stress tolerance. However, it has not been elucidated how melatonin application affects the tomato plant under boron stress. Helicase, calcium-dependent protein kinase and mitogen-stimulated protein kinase families, DEAD-BOX, CDPK, MAPK3, and P5CS, ACS2, FeSOD, CAT2, GR1, APX1 antioxidant defense system genes, has been found that they have high activities under different abiotic stress conditions. The changes in the expressions of these genes were investigated by applying melatonin hormone in tomato plant under boron stress and evaluated for the first time within the scope of this study. In our study, Kayra F1 tomato variety was grown by watering with Hoagland solution for 1 month and then exposed to boron stress of 7.5 mM B(OH)3. With the application of melatonin under boron stress, a decrease in the relative water content, the amount of MDA, the amount of proline, and an increase in the ion leakage were observed compared to the control. When the results were examined, it was determined that the application of melatonin had a decreasing effect on the negative results of boron stress. When the antioxidative enzyme gene expressions of plants under boron stress were examined, no significant difference was observed in P5CS gene expression with melatonin application compared to the control, while a decrease in ACS2 gene expression and an increase in DEAD-BOX, CDPK, MAPK3, APX1, CAT2, GR1, FeSOD gene expressions were observed. When the results were evaluated, it was observed that there was an interaction between stress-related antioxidative enzyme gene expressions and melatonin application. When all these parameters were examined, it was concluded that the application of melatonin to plants under boron stress may be effective in reducing boron stress.