Determination of the mechanisms of resistance of Helianthus annuus L. to drought using the osmopriming method

The purpose of the study is to assess the physiological and antioxidant parameters of sunflower seedlings under osmopriming. Two series of experiments were carried out aimed at: 1) establishing the viability of seeds; 2) assessment of physiological parameters of seedlings. Each experiment included a group of control samples grown under conditions of sufficient moisture and four impact groups exposed to varying levels of osmotic stress. The intensity of accumulation of lipid peroxidation products and the rate of accumulation of reactive oxygen species were determined based on the reaction of malondialdehyde with thiobarbituric acid. Catalase activity was determined photocolorometrically by the interaction of hydrogen peroxide with potassium iodide, the content of chlorophylls a (Cl a) and b (Cl b), carotenoids (Car) - spectrophotometrically in an acetone extract. It has been established that as a result of increasing moisture deficiency, the energy of seed germination decreases in proportion to the increase in the concentration of the osmotic solution. When stress increases to 3.5 atm, seed germination decreases by 29%, and to 8 atm – by 64%. A linear relationship was revealed between the inhibition of the photosynthetic system and the stress factor of moisture deficiency, expressed in a decrease in Cl a by 60% relative to the control with osmopriming of 8 atm. It has been established that a slight decrease in the moisture supply of the substrate causes oxidative stress of cells, as evidenced by a linear increase in malondialdehyde with increasing moisture deficiency. At the same time, antioxidant protection is provided by the enzyme catalase, the concentration of which increases with increasing drought, while low-molecular carotenoids have an indirect effect on the provision of protective antioxidant mechanisms - there is a trend of increasing Cl a + Cl b / Car with a decreasing Cl a / Cl b.