The Effect of Gibberellin and an Ethylene Inhibitor on Twining of Vine Cuttings in Japanese Morning Glory (Ipomoea nil (L.) Roth)

“Twining” along other objects is an important morphogenetic survival response of vine plants. The twining response, induced by the stimulus of touching a supporting object, is a form of “thigmomorphogenesis”. Ethylene is thought to play an important role in thigmomorphogenesis in higher plants, so it is likely to be involved in vine twining. However, the relationship between ethylene and vine twining is not well understood. We used vine cuttings excised from morning glory (Ipomoea nil (L.) Roth ‘Violet’) plants in order to investigate the effect of an ethylene inhibitor on elongation and twining. The vine cuttings required gibberellin for elongation and twining. In the vine cuttings with elongation and twining induced by gibberellin treatment, treatment with 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, significantly decreased the angle of rotation and the spiral pitch of the twining. These results suggest that ethylene may be involved in either sensing a pole via touch and the morphological changes during vine twining or both. We also selected one of the genes for 1-aminocyclopropane-1-carboxylic acid synthase (ACS), which is a key enzyme in the ethylene biosynthetic pathway, with higher expression in tissues on the side touching the pole in twining vines as one of the candidate genes thought to be involved in vine twining in morning glory.