Morphogenesis of rice and Arabidopsis seedlings in space

Seedlings of rice (Oryza sativa L) and Arabidopsis (A. thaliana L.) were cu ltivated for 68.5 hr in the RICE experiment on board during Space Shuttle S TS-95 mission, and changes in their growth and morphology were analyzed. Mi crogravity in space stimulated elongation growth of both rice coleoptiles a nd Arabidopsis hypocotyls by making their cell walls extensible. In space, rice coleoptiles showed an inclination toward the caryopsis in the basal re gion and also a spontaneous curvature in the same direction in the elongati ng region, These inclinations and curvatures were more prominent in the Kos hihikari cultivar compared to a dwarf cultivar, Tan-ginbozu, Rice roots elo ngated in various directions including into the air on orbit, but two third s of the roots formed a constant angle with the axis of the caryopsis. In s pace, Arabidopsis hypocotyls also elongated in a variety of directions and about 10% of the hypocotyls grew into the agar medium. No clear curvatures were observed in the elongating region of Arabidopsis hypocotyls. Such a mo rphology of both types of seedlings was fundamentally similar to that obser ved on a 3-D clinostat. Thus, it was confirmed by the RICE experiment that rice and Arabidopsis seedlings perform an automorphogenesis under not only simulated but also true microgravity conditions.