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.