Involvement of cellulose synthesis in actions of gibberellin and kinetin on cell expansion. Gibberellin-coumarin and kinetin-coumarin interactions on stem elongation

In azuki bean (Azukia angularis = Vignia angularis) epicotyl sections, 5 × 10−4M coumarin inhibited the incorporation of radioactivity from [U−14C]glucose into the cellulose fraction by 35% in the absence of indole-3-acetic acid (IAA) and by 40% in the presence of 1 × 10−4M IAA. There was no inhibitory effect on the incorporation of radioactivity into the other fractions. Coumarin at 5 × 10−4M reversed the promoting effect of 1 × 10−5M gibberellin A3 (GA) and the inhibitory effect of 1 × 10−5M kinetin on IAA-induced elongation of sections with no significant effects on IAA-induced elongation. Neither GA nor kinetin had any appreciable effects on cellulose synthesis. No inhibition of cellulose syntheis was observed with 1 × 10−3M colchichine, which has been reported to have effects similar to those of coumarin on GA- or kinetin-affected stem elongation. Coumarin at 5 × 10−4M was ineffectual in breaking up wall microtubules, while a disrupting effect on wall microtubules was clearly demonstrated with 3 × 10−4M colchicine. From these results, the possible involvement of cellulose synthesis in cell expansion controlled by GA or kinetin was suggested.