The effect of combined boric acid and temperature stress on some ecological parameters, antioxidant enzymes and gene expression in sunflower plant (Helianthus annuus L.)

The changes in climatological conditions have negative effects on the ecological, physiological, and molecular metabolic activities of plants; it adversely affects plant yield, quality, and production. In addition to temperature, another factor that causes abiotic stress in plants is the amount of macro and micronutrients in the soil. The boron element, which is within the micronutrients, is in the elements that plants react most to. Boron element is effective in important metabolic events in the plant such as membrane permeability, root growth, nucleic acid, and ATP synthesis. It suggests that boron may inhibit or promote another abiotic stress factor that affects plants. Although there are studies about the effects of temperature or boron on plants in the literature, there are no studies unraveling the combined effects of boron element on plant metabolism, which are applied simultaneously at different temperatures. In this study, individually and combined effects of heat and boron application were investigated. Root and stem length, root and stem wet-dry weight, root and stem biomass, boric acid tolerance index, lipid peroxidation, total protein amount, SOD, CAT, APX enzyme activities, and changes in gene expression levels of these enzymes were determined in sunflower plants grown at 15, 25 and 40°C and treated with 10 mM and 25 mM boric acid. As a result, the ecological parameters of the root and stem decreased due to the increasing boric acid concentration of the plants at 25 and 40°C. Besides the ecological parameters of the root and stem were positively affected and increased at 15°C in contrast to the studies on low temperature in the literature has been determined. Antioxidant enzyme activities and mRNA levels of root and leaf samples increased at 40°C. However, antioxidant enzyme activities and mRNA levels increased in root samples and decreased in leaf samples at 15°C. When ecological parameters are examined, interestingly it has been revealed that the application of high boron concentration at low temperature encourages the growth of the plant, and when the antioxidant enzyme activities and mRNA expression levels are examined, it has been shown that the plant is very effective in tolerating low-temperature stress.