[Effect of weightlessness on the water fern Azolla]

An exposure to 6-day weightlessness of the fern Azolla pinnata R. Br. symbiotically related to the nitrogen fixing alga Anabena azollae did not affect the main biological characteristics (growth, development and morphological structure) of both fern plants and algae. The exposure did not influence the growth rate or subsequent Azolla generations on the Earth.