Auxin-gibberellin relationships in. their effects on hypocotyl elongation of light-grown cucumber seedlings IV. Inhibition of IAA-induced elongation by N,N′-dicyclohexylcarbodiimide and its reversal by gibberellin A3

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Abstract
IAA-induced elongation and control growth of light-grown cucumber hypocotyl sections were markedly inhibited by DCCD, an inhibitor of membrane-bound ATPases. The concentration effective for inducing marked inhibition was more than 10−5 M. At 10−5 M DCCD, there was an apparent antagonism between IAA and DCCD. At 5 × 10−5 M DCCD, the inhibition was partially recovered by 10−4 M of IAA. The results might indicate a close association of the auxin action with membrane-bound ATPases. The DCCD inhibition was so strong that treatment with 10−4 M DCCD for about 5 min significantly suppressed further growth and longer incubation killed the sections. In contrast, DCCD had not inhibitory effect on both control growth and IAA-induced elongation if GA3 was present simultaneously. DCCD treatment followed by GA3 treatment still resulted in the inhibition, suggesting that the inhibition was not reversible. In order to obtain reversal of DCCD inhibition by GA3 both compounds must be present at the same time. The GA3 effect is discussed in connection with the mechanism of DCCD action on membrane-bound ATPases.