Effect of copper ions on the composition of phytosterols of the vacuolar membrane of Beta vulgaris L.

The study set out to investigate the effect of different concentrations of copper ions on the composition of phytosterols of the vacuolar membrane (tonoplast) of beetroot (Beta vulgaris L.). To characterise the stress caused by the action of copper ions, a conductometric study of the permeability of cell membranes and the level of lipid peroxidation was carried out. The results demonstrate an increase in these indicators in beetroot tissues. Among tonoplast phytosterols, β-sitosterol, stigmasterol, campesterol, and cholesterol were studied. In cell membranes, these phytosterols perform a structural function, contributing to lipid microdomain formation, influencing plant growth and development, and participating in plant responses to stress. The study of the effect of copper ions on tonoplast phytosterols showed most of them to be occupied by the free form. In the presence of 100 μM copper, a significant increase in campesterol content was detected. The ratio of stigmasterol/β-sitosterol and 24-methyl-/ ethylsterol, which may influence the stress response of plants, is an important indicator of plant membrane health. The observed increases in the ratios of stigmasterol/β-sitosterol and 24-methyl-/ethylsterols can be explained in terms of mechanisms for regulating the functioning of the tonoplast under stress caused by copper ions. Thus, the obtained results may indicate the participation of cell membranes, including tonoplast, in the mechanisms of adaptation of beetroot tissue cells to stress caused by copper ions.