Viter A. Legume-rhizobia symbiosis formation under clinorotation.

The thesis deals with the development of technology of exploration of legume-rhizobia system under simulated microgravity conditions in the artificial ecosystems: clinorotation and permanently inverted orientation of plants for the gravity vector. It has been established that researches of such a system required a long-term clinorotation (at least 50 days) as well as using of a mineral fiber with periodically controlled wetness for soil substitution; these conditions should be combined with illumination with light intensity about 2,5 klx; as a macrosymbiont should be used a plant with genetically determinate unerect stem and with a sufficient ecological plasticity, in particular, shade tolerance. These requirements are met by alfalfa Medicago sativa L. cv. Yaroslavna. The central part of the dissertation research elucidates the analysis of the differences in the responses of alfalfa, inoculated and uninoculated with high-effective strain Sinorhizobium meliloti 441 to the impact of clinorotation and a permanently inverted orientation. A series of indices such as an aerial part and root dry weight; linear dimensions of various parts of shoots; nitrogen metabolism intensity (nitrogen-fixing activity, crude protein and nucleic acids content); photosynthetic processes intensity (photosynthetic pigments content, photochemical efficiency (Fv/Fmax), lectin-containing extracts activity (indirect indicator for adaptation syndrome passing) were applied in order to achieve this object. 50-day clinorotation has been observed to result in the rise of the smallest nodules (up to 0.1 mm3) portion. This might prove that the simulated microgravity facilitates not only the growth but the initiation of young nodules. Several indices have appeared to be the most expressive in response of the symbiotic system to clinorotation and a permanently inverted orientation impact. Thus, nitrogenase activity in 30-day-old plants set with the following ascending order: clinorotation<permanently inverted orientation< ordinary stationary conditions (control), while in 50-day-old plants an opposite order was noted. Higher RNA:DNA ratios in 30-days plants were fixed as a result of treatment with S. meliloti 441, regardless of the variant of plant orientation for gravity vector. Crude protein content in the plants of the same age was characterized by an ascending order: control<permanently inverted orientation<clinorotation. The impact of clinorotation facilitated increase in the chlorophylls content while under condition of permanently inverted orientation chlorophylls and carotenoids contents have risen. On the 50th day of the experiments either no differences or decreases in photosynthetic pigments content were observed with simultaneous slight decrease of the Fv/Fmax index were observed. Hemagglutination reaction for both 30- and 50-day-old plants trended for ascending order: ordinary stationary conditions (control)<clinorotation<permanently inverted orientation. Such trend might testify that the altered gravity conditions evoked stress in the plants and, moreover, that Medicago sativa possessed high adaptive ability for the stressors caused by these conditions. Consequently, exposition of alfalfa to the conditions of both clinostat and under condition of permanently inverted (180 ?) orientation appeared to be stressors for the plants during the first ten-day periods. At the same time these conditions weren't noted to depress nitrogen-fixing microorganisms and the process of Medicago sativa roots nodulation. The conducted investigations might testify that the pre-sowing treatment of seeds with S. meliloti 441 can facilitate Medicago sativa adaptation to the simulated microgravity conditions during the 4th and 5th ten-day periods of vegetation.