Comparison of Changes in the Content of Plasma Membrane and Tonoplast Sterols under Oxidative and Osmotic Stress

We compared oxidative and osmotic stress-induced changes in sterol content in plasma membranes and tonoplasts isolated from stored beet (Beta vulgaris L.) roots. The most significant differences between the membranes under all studied stresses were observed in the cholesterol content: it decreased in the plasmalemma, but increased 4-6 times in the tonoplast. Similar changes were observed for other sterols, but in different ways under different types of stress. Particularly noticeable differences were noted under hyperosmotic stress. The increase in the content of sterols was much more pronounced in the vacuolar membrane compared to the plasmalemma. This observation allows us to conclude that tonoplast plays a more significant role in protection of the plant cell from stress compared to plasmalemma.