Growth and development in Arabidopsis thaliana through an entire life cycle under simulated microgravity conditions on a clinostat

The effects of simulated microgravity conditions produced by a horizontal c linostat on the entire life cycle of Arabidopsis thaliana ecotype Columbia and Landsberg erecta were studied, Horizontal clinorotation affected little germination of seeds, growth and development of rosette leaves and roots d uring early vegetative growth stage, and the onset of the bolting of inflor escence axis and flower formation in reproductive growth stage, although it suppressed elongation of inflorescence axes. The clinorotation substantial ly reduced the numbers of siliques and seeds in Landsberg erecta, and compl etely inhibited seed production in Columbia. Seeds produced in Landsberg er ecta on the clinostat were capable of germinating and developing rosette le aves normally on the ground. On the other hand, growth of pin-formed mutant (pin/pin) of Arabidopsis ecotype Enkheim, which has a unique structure of inflorescence axis with no flower and extremely low levels of auxin polar t ransport activity, was inhibited and the seedlings frequently died during v egetative stage on the clinostat. Seed formation and inflorescence growth o f the seedlings with normal shape (pin/+ or +/+) were also suppressed on th e clinostat These results suggest that the growth and development of Arabid opsis, especially in reproductive growth stage, is suppressed under simulat ed microgravity conditions on a clinostat, To complete Be life cycle probab ly seems to be quite difficult, although it is possible in some ecotypes.