The paper deals with the results of space experiment, which was carried out on an original automatically operating centrifuge „Neris-5“ on board of the satellite „Bion-10“ in 1993. The peculiarities of gravisensing system formation in roots of garden cress (Lepidium sativum L.) seedlings grown in microgravity under simulated and natural gravity of 1g in space and on the ground, respectively, are presented. Quantitative study on the growth of root columella cells (statocytes), the state of their intracellular components, and the location of amyloplasts was performed by light and electron microscopy.

The growth of statocytes in microgravity and under 1g in space did not differ significantly though the loca­tion of amyloplasts experienced significant changes: it depended on the gravity and cell position in columella. Instead of the concentration of amyloplasts at the distal cell region of roots grown under 1g, most plastids in microgravity-grown roots were accumulated at the centre of statocytes. The obtained data on the formation and state of intercellular plastids confirm the supposition that the environment of microgravity alters the metabolism of plant cells; however, its alterations are not fateful for the formation of gravisensing cells and for the growth of the whole root.