2014 Volume 28 Pages 6-11
Seedlings of azuki bean were cultivated under microgravity conditions in space during SSAF2013 program, and then growth, morphology, and the cell wall rigidity of their etiolated epicotyls were analyzed. Epicotyls grown on the ground oriented vertical direction, whereas epicotyls grown in space oriented oblique upward direction away from the cotyledons. The length of epicotyls grown in space was varied, but the proportion of seedlings with larger epicotyls was higher than that of the controls. These results indicate that growth and morphology of epicotyls are modified under microgravity conditions in space. On the other hand, the breaking load of epicotyls was analyzed using a spring balance for determination of the cell wall rigidity of epicotyls. The breaking load of epicotyls grown in space tended to be smaller than that of controls. Also, epicotyls grown in space had resistance to bending than the controls. Thus, microgravity affected the cell wall rigidity of epicotyls. Taken together, azuki bean seedlings performed an automorphogenesis and cell wall modification under microgravity conditions. Under microgravity conditions, where plants need not to resist the gravitational force, the body shape and the cell wall rigidity of stems may be modified.