Abstract
Ethylene increases the molecular mass of xyloglucans, thereby inhibits elongation growth of azuki bean epicotyls. We found that the reorientation of cortical microtubules from transverse to longitudinal directions was involved in ethylene-induced lateral expansion of azuki bean epicotyls. To clarify the relationship between the inhibition of elongation growth and the promotion of lateral growth, we investigated the effects of anti-microtubular reagents, colchicine, oryzalin and propyzamide, on the amounts and the molecular mass of xyloglucans. These reagents inhibited longitudinal growth and promoted lateral growth of azuki bean epicotyls. The ratio of xyloglucan level to cellulose level was increased by the reagents. The reagents also increased the weight-average molecular mass of xyloglucans, as observed in ethylene-treated epicotyls. These results suggest that, when lateral growth is promoted, metabolic turnover of xyloglucans is generally modified, leading to the increase in their molecular masses.
