Enhancement of transpiration by ethylene is responsible for absence of internodal elongation in floating rice at low humidity.

Internodal elongation in floating rice (Oryza sativa) is known to be enhanced by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH). However, ethylene-induced internodal elongation is inhibited at low RH, while GA3-induced internodal elongation is hardly affected by humidity. We examined the effects of ethylene and GA3 on the rate of transpiration in stem segments incubated at 30 percnt; or 100 percnt; RH. Ethylene promoted the transpiration of stem segments at 30 percnt; RH, but not at 100 percnt; RH, while GA3 had little effect on transpiration at either 30 percnt; or 100 percnt; RH. We propose that the absence of ethylene-induced internodal elongation at low RH is due, at least in part, to ethylene-induced transpiration.