PROTECTIVE EFFECT OF HUMIC ACID AGAINST HEAVY METAL STRESS IN BARLEY GROWN NEAR HIGHWAYS

Along with rapid urbanization and industrialization, the entry of heavy metals into agricultural land through intensive human activities has increased in the past few decades and consequent soil pollution is at a remarkable level. The persistence of heavy metals and their movement through the food chain have led to intensive studies in this area. In particular, studies are conducted on issues such as preventing the spread of heavy metals, removing them from the environment and reducing their negative effects. In our study, the effect of humic acid in Tarim-92 barley type exposed to heavy metal pollution on the highway was investigated. Tarim-92 barley seeds were grown at a distance of 10, 20 and 40 meters from the highway. The amounts of Cr, Cu, Pb, Ni, Cd heavy metals in barley samples were measured with ICP-Ms. It was determined that the amount of heavy metal decreased as the distance to the highway increased, Retrotransposon activity was assessed by IRAP, and 21.87%, 15.62% and 12.50% polymorphism rates were obtained in samples at 10, 20 and 40 meters to the highway, respectively. In the samples where humic acid was applied, it was found that the polymorphism values at the same distances were reduced to 18,75%, 12.50% and 9.37%, respectively, miRNA 156 and miRNA 159 gene expression analyses were conducted, and it was identified that heavy metals caused an increase in the miRNA levels of barley. It was determined that the applied humic acid reduced the amount of heavy metal in the structure of barley and relieved the heavy metal stress. While in Group 1 samples without humic acid application 21%, 25% and 37% reductions in miRNA 156 gene expression level were obtained, in Group 2 samples with humic acid application, 15%, 23% and 46% reductions in miRNA 159 gene expression level were determined It can be stated that in agricultural products exposed to abiotic stresses such as heavy metal, humic acid has a protective effect and reduces the level of stress.