[Response of siphoneal alga (Vaucheria sessilis) to the gravity factor]

Growth and development of siphonal alga Vaucheria sessilis under changed gravity and the role of cytoskeletal structures in gravitational response were studied. Hypergravity (3 g) and "hypogravity" were generated by slow clinostating at 7-8 rev/min and rapid clinostating at 35, 70, 135 rev/min, respectively. The experiments in microgravity were flown aboard biosatellite Bion-11. As was shown, V. sessilis responded to changed gravity by inhibition of rate of growth and increasing the number of nuclei in the strand as a result of activation of mitotic processes. Modulation of the course of the gravitational response with anticytoskeletal agents points to involvement of the cytoskeleton. The cortical circuit of actin microfilaments and the cytoplasm stream directed by this structure appear to be the most sensitive to changes in gravity. Gravity-sensitive V. sessilis is another promising object of research in the field of gravitational biology.