The influence of osmotic stress on the content of calcium ions in the red beet vacuoles and on the transport activity of tonoplast proton pumps

The contents of calcium ions in the isolated vacuoles and in intact red beets under the conditions of dormancy and osmotic stress was determined. It is demonstrated that the content of calcium ions in the red beet vacuoles not exposed to osmotic stress makes 13.3% of the total content these ions in intact red beets. Under the conditions of osmotic stress, this indicator increases substantially. Furthermore, under the conditions of hyperosmotic stress, the content of calcium ions in the vacuoles was 30%, while under hypoosmotic stress it was 49% of the total content of these ions in the intact red beet. The transition of calcium ions from the cytoplasm and other compartments into the vacuole under the conditions of osmotic stress is, probably, one of forms of participation of the vacuole in adaptation processes of the plant cell under this kind of abiotic stress. It has been demonstrated for the first time that tonoplast proton pumps, which actively participate in provision of calcium homeostasis in cytoplasm, substantially activate their transport activity under osmotic stress, what allows one to speak about their important role in the cell’s protective programs. Under normal (no stress) conditions, artificial elevation of the content of calcium ions led to inhibition of activity of the tonoplast proton pumps, while under gipoosmotic stress the activity of tonoplast proton pumps increased, what might aid to restoring homeoctasis with respect to calcium ions in cytoplasm

The Influence of Gasotransmitters on Membrane Permeability and Activity of Tonoplast H+-ATPase Under Oxidative Stress

The investigation of the influence of gasotransmitters – a new class of signaling molecules – on the root tissues of red beet (Beta vulgaris L.) was conducted. It was found, that hydrogen sulfide (H2S) had some stabilizing effect on cellular membranes, reducing their permeability detected with the aid of conductometric technique. The reliable influence of carbon monoxide (CO) and nitrogen oxide (NO) in our experiments was not observed. A significant increase in efflux of electrolytes from beet tissue under oxidative stress was observed. The addition of gasotransmitters failed to reduce it reliably. Under normal conditions, no appreciable effect of gasotransmitters on tonoplast H+-ATPase transport activity was found. Under oxidative stress, NO and H2S increased the H+-ATPase activity, reduced significantly by the impact of hydrogen peroxide, but did not recover it completely. CO enhanced the negative impact of oxidative stress, and reduced H+-ATPase transport activity. The results obtained suggest a possible conclusion that the gaseous signaling molecules take part in the regulation of transport processes in plant cell through the control of H+-ATPase activity under oxidative stress

Changes in Composition of Vacuolar Membrane Lipid Fatty Acids Under Osmotic Stress

The investigation of influence of different types of osmotic stress (hypo- and hyperosmotic) on the composition of vacuolar membrane lipid fatty acids of red beet root (Beta vulgaris L., variety Bordeaux) was conducted. Noteworthy, the plenty intensive stress impact didn't cause the conventional nonspecific reaction bound up with the increase of the unsaturated fatty acid content regulating membrane microviscosity. This feature apparently can be explained with the location and biochemical characteristics of the scrutinized membrane. Some reliable increases of the content of the short-chain saturated fatty acids (C14:0+C15:0) under hyper osmotic stress and the content of the long-chain saturated fatty acids (C22:0+C23:0) under both types of osmotic stress were found. It was proposed that the revealed changes in the content of saturated fatty acids of red beet root vacuolar membrane lipids were specific, and corresponding fatty acids were the most sensitive to osmotic stress impact

Evaluation of the Effect of Oxidative Stress on Roots of Red Beet (Beta vulgaris L.)

In the present investigation it was studied the effect of oxidative stress on root of red beet. The degree of stress exposure was assessed at various levels: in tissues of roots (conductometric method), on isolated vacuoles (time-lapse video recording), and transport activity of the vacuolar membrane enzyme, namely V-H+-ATPase (fluorescent probe method). The obtained results allow to conclude the negative effects of oxidative stress on different levels of plant organization. There were several effects: a significant increase of outflow of electrolytes from the tissues of roots, a great decrease of half-life time of isolated vacuoles, and a 2 times reduction of transport activity of tonoplast H+-ATPase. Thus, the methods used in this study can be applied to assess the intensity of the impact of oxidative stress on plants