Abstract
Hypergravity increases cell wall rigidity by increasing the molecular size of xyloglucans in dicotyledonous plants. The molecular size of cell wall polysaccharides is determined as a balance between the synthesis and the depolymerization. In the present study, we examined the effects of hypergravity on both processes of xyloglucans. Azuki bean cuttings were incubated with [6-3H]-L-fucose. 3H-Xyloglucans were eluted in the higher molecular mass regions than total xyloglucans detected by the iodine method. Hypergravity did not influence the molecular size of newly deposited xyloglucans. 3H-Xyloglucans obtained from epicotyls grown at 1 g were shifted to the low molecular mass regions during the incubation period, which was inhibited by hypergravity. These results indicate that xyloglucans were deposited into the cell wall as large molecules but they were then demolymerized in the cell wall. Hypergravity-induced inhibition of the depolymerization is involved in the increase in the molecular size of xyloglucans under hypergravity conditions.
