Biological Sciences in Space

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The life cycle of Arabidopsis plants was examined by growing them on a horizontal clinostat. Seeds on agar media were allowed to germinate and seedlings were grown under a simulated microgravity on a horizontal clinostat. Clinorotation (3 rpm) did not appear to interfere with germination of plant seeds and development of cotyledons and leaves. Stress relaxation parameters of the cell wall, the minimum relaxation time and the relaxation rate did not appear to be affected by clinostat rotation. On the other hand, the length of inflorescences was reduced to 61-62% by clinostat rotation. Rotation was found to inhibit the polar transport of auxin, although inflorescence growth and auxin transport were not completely inhibited. From these facts, it is possible that the life cycle in Arabidopsis plants could be accomplished in space, although growth phenomena involving auxin transport and its action may be disturbed. Plants may have a capacity to grow in space and we may be able to cultivate crops in space.

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We have examined the effect of non-injurious mechanical stimulation on callus formation of stem tissues. Mechanical stimulation by rubbing substantially promoted the wound-induced callus formation on the stems of beans(Phaseolus vulgaris L.). The promotion of callus formation also was observed in in vitro culture of the tissues excised from mechanically stimulated stems of beans. The results imply that mechanical stimulation induces some pysiological changes preference for cell division in developing callus.

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