Influence of nonuniform magnetic fields on orientation of plant seedlings in microgravity conditions.

Experiments on the spatial behavior of the flax (Linum usitatissimum, L.) seedlings in a nonuniform magnetic field were conducted on the orbital space stations "Salut" and "Mir". This field can displace sensory organelles (statoliths) inside receptor cells and such displacement should cause a physiological reaction of the plant-tropistic curvature. Experiments were conducted in the custom-built "Magnetogravistat" facility, where seeds were germinated and grown for 3-4 days in a magnetic field with the dynamic factor grad (H2/2) approximately equal to 10(7) Oe2/cm, then fixed on orbit and returned to Earth for analysis. It was found, that 93% of the seedlings were oriented in the field consistently with curvature in response to displacement of statoliths along the field gradient by ponderomotive magnetic forces, while control seedlings grew in the direction of the initial orientation of the seed. This suggests, that gravity receptors of plants recognized magnetic forces on statoliths as gravity, and that gravity stimulus can be substituted for plants by a force of a different physical nature.

Peculiarities of biological processes under conditions of microgravity.

The results of experiments aboard spacecraft demonstrated the dependence of the pattern of biological processes on microgravity and on the ability of biological objects to adapt themselves to new environmental conditions. This is of fundamental importance for solving theoretical and practical problems of space biology, or elaborating the theory of organism's behavior in weightlessness, and for elucidating the global mechanisms of the action of microgravity on living systems.

Peculiarities of the submicroscopic organization of Chlorella cells cultivated on a solid medium in microgravity.

The submicroscopic organization of Chlorella vulgaris cells (strain LARG-1) growing over 30 days on a solid agarized medium aboard the orbital station "Mir" was studied. A number of differences in the ultrastructure of cells of the experimental population compared to the control has been revealed. Thus, changes in the membrane system of plastids, in particular, appearance of numerous vesicles of different diameter and outgrowths of the plastids and their contact with the plasmalemma as well as a considerable decrease of reserve polysaccharide number in the plastids. Moreover, an increase in the size of mitochondria, their cristae and lipid drops in cytoplasm, the formation of more complicated configuration folding of plasmalemma and appearance of small-granular material of mean electron density in the periplasmic space of Chlorella cells grown during space flight, are demonstrated. Comparative cytological analysis has revealed general regularities of rearrangements of the submicroscopic organization in Chlorella cells cultivated on both solid and semiliquid agarized nutrient media.

[Characteristics of Triticum vulgare in the early phases of development (ontogenesis) in space flight]. / Osobennosti Triticum vulgare na pervykh fazakh razvitiia (ontogeneza) v usloviiakh kosmicheskogo poleta.

The effect of space flight factors on the growth and development of wheat grown in a Svetoblock-M unit on the orbital station Mir was investigated. The data obtained allow the conclusion that wheat plants develop flight-induced changes. When compared to control plants, experimental plants show a delayed growth in terms of biometric parameters, different distribution of biogenic elements, lower phytoncidal activity, increased bacterial and fungal contamination, and a changed pigment and lipid composition.

The development of seedling shoots under space flight conditions.

The assumption that gravity is the major factor in the process of formation of plant polar axis was used as a working basis for the experiment. It was hypothesized by Merkys in 1973 that the effect of gravity related to axial polarity is similar to the process which determines the lateral polarity of shoots under the influence of gravity. There are two possibilities: (i) the development and morphogenesis of shoots takes place directly under the influence of gravity, or (ii) this process, at least during the first growth phases, is determined in the course of the germ development in the seed. In accordance with that assumption, the experiment was carried out in 1973. A special system was used for germinating and cultivating "Pioneer" and "Grybovsky rannyj" peas. The duration of the experiment under flight conditions was 48 hours in darkness, at 20 degrees C. The experimental conditions were the following: 1, the experiment in flight; 2, imitation of flight conditions using the horizontal clinostat; 3, vertical clinostat; 4, control (vertical plants). When the system was brought down to earth, the material was fixed and subjected to morphological and biochemical analysis. On the basis of the analysis, the following conclusion was drawn: during the first growth phases, the morphogenesis of shoots and roots apparently does not change under flight conditions. This conclusion was confirmed by planting those seedlings under earth conditions; normal plants were obtained whose growth and development were similar to the control seedlings. The problem of the influence of changed gravity, or the lack of it, on the growth and development of plants is discussed. The possible role of gravity on the formation of the polarity axes is also discussed from the point of view of generative development and the determination of some peculiarities of morphogenesis.

Effects of space flight factors on the heredity of higher and lower plants.

The effects were studied of a long-term space exposure (72 days) aboard the Salyut orbital station on the following: dry seeds of Crepis capillaris (L.) Wallr. and Arabidopsis thaliana (L.) Heynh, haploid and diploid strains of Saccharomyces cerevisiae mutant for adenine locus (ad) and strain LARG-I of Chlorella vulgaris Beijer. A modifying effect of space factors on radiobiological action of gamma-irradiation from 137Cs was determined with the higher plant seeds and Chlorella culture. For this, the material was partly irradiated prior to, and partly after the flight at doses of 3, 30 and 10 kr for C. capillaris, A. thaliana and Chl. vulgaris, respectively. It was shown that: (1) Space factors caused reduced survival of Arabidopsis seedlings and Chlorella and yeast cultures, reduced productivity of Chlorella cells, increased mutability of Chlorella and yeast cells and increased frequency of chromosome aberrations in cells of Crepis root meristem. There are, however, a few exceptions: cell germination of C. capillaris was enhanced while mutability of A. thaliana seeds declined. (2) Space factors increased the adverse effects of the pre-flight irradiation on all the parameters of the cultures tested. (3) Space factors had no genetic effect on the objects tested. They have, however, caused a stronger inhibition of seed germination and augmenting survival of A. thaliana seedlings and Chlorella cells.

Effects of space flight factors on Drosophila.

Drosophila melanogaster flies of strain D-32 were exposed aboard the Soyuz 10 spaceship. An insert with a nutritional medium and insects was placed in a small on-board thermostat (Biotherm II) providing a constant temperature (24 degrees C +/- 1 degree) for Drosophila development. The frequency of dominant lethals was determined in the females. Dominant, autosomal and sex-linked recessive lethals were estimated in hatching virgin males and females; the time of hatching was rigorously fixed. Sex-linked recessive lethals were related to certain stages of gametogenesis. The 1-5 oocyte stage showed an increased sensitivity to space-flight factors as regards the frequency of both dominant and recessive lethals.