Ethylene is responsible for a disturbed development of plant reproductive system under conditions of space flight

The development of reproductive organs was studied on three dwarf cultivars of wheat Triticum aestivum and the fast-cycling Brassica rapa plants, grown under earth control conditions, during the space flight in the "Mir" orbital station, and in a earth experiment that simulated growth conditions during the space flight, including an elevated content of ethylene in the air (1 mg/m(3) on average). We found that the embryological characteristics of the plants were not affected by space flight conditions. The elevated ethylene content in air resulted in some changes in the morphometric characteristics of inflorescences and a greater frequency of sterility similar under conditions of space flight and control earth experiment. We conclude that the abnormalities and modifications in the development of reproductive organs, induced by space flight conditions, were caused by a secondary factor, an elevated ethylene content in the cabin air, rather than by microgravity.