The effect of humic acid on some physiological parameters and gene expressions in tomato (solanum lycopersicum) under salt stress

This study was carried out to determine the effect of salt stress on tomato plants and to demonstrate the effects of humic acid application on salt stress. For this purpose, plants belonging to Kayra F1 tomato variety were exposed to a dose of 150 mM NaCl and humic acid application was performed as 3 ml/l. In the study, shoot fresh/dry weight, root fresh/dry weight, shoot/root length, proline, chlorophyll, MDA, ion leakage amounts, antioxidative enzyme gene expressions such as CAT, SOD, GR and APX were investigated. As a result of the study, it was determined that the application of salt+humic acid compared to the salt application caused a significant increase in shoot fresh/dry weight, root fresh/dry weight, shoot/root length and chlorophyll values. In addition, it was found that ion leakage, MDA and proline values decreased by applying humic acid to salt treated plants. When these parameters are examined, the positive effect of humic acid application was observed against the negative effects of salt application. When antioxidative enzyme gene expressions were evaluated in the study, it was found that application of humic acid to plants under salt stress did not make any difference in SOD gene expression while increasing APX gene expression and decreasing CAT and GR gene expression. These results showed that humic acid application is effective on stress-related antioxidative enzyme genes and tolerance mechanisms and that this effect may be positive. As a result, it was concluded that humic acid, which will be applied to plants under salt stress conditions, can play an effective role in reducing salt stress.