Abstract

The study of the mechanisms of adaptogenic action of furostanol glycosides (FG) on plant cells was carried out in vitro and a comparison was made of the effects of hypothermia and hyperosmotic stress on a suspension cell culture of Medicago sativa L. It has been shown that the cell population of M. sativa in vitro possesses functional specificities that determine different sensitivity to the action of these abiotic stressors, which was expressed in different levels of cell viability: high (85%) under hypothermia and low (25%) under hyperosmotic action. Hypothermia stimulated the rate of generation of superoxide anion (\({\text{O}}_{2}^{{\bullet - }}\)), and it was accompanied by a high constitutive activity of antioxidant enzymes (guaiacol-peroxidase, ascorbate peroxidase and glutathione peroxidase), the level of which reflects the compensatory potential of cells. Preservation of a high level of cell viability under the action of hypothermia, despite a 40% increase in the rate of generation of \({\text{O}}_{2}^{{\bullet - }}\), indicates that the formed reactive oxygen species did not cause damage to lipid structures and macromolecules in cells. Exogenous treatment with FG with this type of stress effect promoted an increase in the activity of antioxidant enzymes but did not have a noticeable effect on the initially high level of cell viability. In conditions of hyperosmotic stress, preliminary exposure to FG led to a threefold increase in cell survival (from 25 to 73%) and a 30% increase in the activity of soluble peroxidase in comparison with its level under the influence of only a stressor. Exposure to FG also caused an increase in activity antioxidant enzymes, a decrease in the level of lipid peroxidation and an increase in the activity of enzymes of the malate dehydrogenase (MDH) complex. However, in contrast to hypothermia, the observed changes caused a significant increase in the viability of M. sativa cells in vitro. An increase in the formation of osmolytes in the reactions NAD/NAD·H-MDH was indicated by the increased concentration of osmotic (mannitol), which causes the initial degree of cell plasmolysis, in comparison with the control. The article discusses specificities of M. sativa cell culture influencing the specificity of its stress-resistance, possible mechanisms of cell protection in vitro in hypothermia and hyperosmotic stress and the role of FG in these processes.