[Weightlessness and elementary biological processes]

This book gives comprehensive review of the role of gravity in fundamental biological processes. The book surveys the results of experiments on precellular and unicellular organisms, plant and animal cultured cells and tissues, fungi and actinomycetes, higher plants, and insects. The book discusses essentially every experiment performed in real flights, including those in which the combined effect of microgravity and ionizing radiation was investigated, as well as many clinostat and centrifuge studies. In orbital flights unicellular organisms exhibited no gravity-dependent processes. The maximum size and basic morphology of unicellular organisms developed obeying the second law of thermodynamics do not therefore depend on space or time. Fungi retained all their properties except for gravitational ordering. Higher plants developed normally through seed-to-seed cycles: from the stage of seed germination to that of maturation of next generation seeds. Plants changed all their gravity-dependent movements. Since plant movements are irreversible, this affected their final shape, although the basic structure and size remained unaltered. The frequency of spontaneous and radiation--induced mutations changed insignificantly. The rotation of generations of plants and animals taken under study developed in a normal way. The morphological, physiological and genetic status of present-day organisms has developed under the effect of the gravity force that plays three different parts: as the creator and transformer of the abiotic environment, as the factor of natural selection, and as the factor of environmental physiology eliciting stable mechanical stresses. The effects of these gravity roles are implemented by different mechanisms and actualized in different time scales. The uneventful development of the basic biological processes in microgravity is an important factor that makes possible long-term space missions. From this point of view, the road to outer space is open to man in terms of his biology.