Endogenous Brassinosteroids Are Involved in the Formation of Salt Resistance in Plants.

The endogenous brassinosteroid (BS) profile was for the first time shown to change in response to salt stress in potato plants. A group of 6-keto-BSs was identified and found to significantly increase in content during salinization in contrast to other groups of hormones examined. A tenfold reduction in the level of endogenous BSs in mutant Arabidopsis thaliana plants with impaired biosynthesis (det2) (or reception (bri1)) of phytosteroids decreased their salt resistance, as evidenced by a lower efficiency of photochemical processes of photosystem II (PSII) and growth inhibition. The results confirmed the idea that endogenous BSs are involved in the formation of salt resistance in plants.

Polymetallic Stress Changes the Endogenous Status of Brassinosteroids and Reduces the Effectiveness of Photochemical Reactions Photosystem II in Barley Plants.

The effect of polymetallic stress (Mn2+, Cd2+, Cu2+, Ni2+, Zn2+, Pb2+, and Al3+) of different duration and intensity on the endogenous brassinosteroids (BS) content and photochemical activity of photosystem II in barley plants was studied. The content of steroid hormones was determined by a two-stage enzyme immunoassay. It was established for the first time that barley plants responded to polymetallic stress by changing the endogenous content of various phytosteroid groups (24S-methylBS, 24-epiBS, 28-homoBS, B-lactoneBS, and 6-ketoBS). It was shown that the stress-dependent dynamics of changes in the endogenous content of various BS groups is characterized by organ specificity and is determined by the age of plants, the intensity of the acting stressor, and the specificity of brassinosteroids. The observed changes in the endogenous status of BS in barley plants under polymetallic stress are accompanied by inhibition of growth processes, a decrease in the content of the main photosynthetic pigments, and a slight decrease in the efficiency of photochemical processes in PS II (Fv/Fm, ETR, qN, and NPQ). Considering the multifunctional stress-protective effect of brassinosteroids, it is assumed that the change in the endogenous status of BS against the background of polymetallic pollution is adaptive and allows minimizing the damaging effects of toxic heavy metals and aluminum.

Exogenic Melatonin Reduces the Toxic Effect of Polymetallic Stress on Barley Plants.

The effect of melatonin on growth parameters, the photochemical activity of photosystem II (PS II), the content of the main photosynthetic pigments, and lipid peroxidation in barley plant leaves under polymetallic stress were studied. Melatonin reduces the toxic effect of polymetals on biomass accumulation, root growth, and maintenance of the assimilating surface. The protective action of the hormone is based on its ability to reduce the intensity of oxidative stress by maintaining the level of carotenoids and increasing the activity of superoxide dismutase, but not by regulating the photochemical activity of chloroplasts. The effectiveness of melatonin does not depend on the duration of exposure. The data obtained can be the basis for optimizing the use of melatonin as a plant priming inducer.

Melatonin Supports Photochemical Activity of Assimilation Apparatus and Delays Senescence of Leaves of Monocotyledonous Plants.

Melatonin supports the photochemical activity of photosystem II (PS II) and slows down the degradation of the main photosynthetic pigments during aging of leaves of monocotyledonous plants. The protective effect of melatonin is manifested in an increase in the maximum (Fv/Fm) and effective (Y(II)) quantum yield of PS II, in an increase of regulated (Y(NPQ)) and a decrease in unregulated dissipation of excitation energy (Y(NO)). These effects are based on the ability of melatonin to reduce the intensity of oxidative stress by maintaining a high level of carotenoids, which exhibit pronounced antioxidant properties, during aging.

[The effects of mexidol in pain syndromes]. / Effekty meksidola pri bolevykh sindromakh.

Models of neuropathic pain syndrome and adjuvant arthritis were used to study the effect of mexidole, an antioxidant from the 3-hydroxypyridine group. Mexidole was indicated to produce no preventive effect in pain syndromes, but to exhibit a therapeutic one. The use of mexidole in combination with the agents activating the monoaminergic systems in the central nervous system showed the presence of their reciprocal effect in neuropathic pain syndrome and its absence in adjuvant arthritis. Possible mechanisms of action of mexidole were also discussed.