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 (GA(3)) at high relative humidity (RH). However, ethylene-induced internodal elongation is inhibited at low RH, while GA(3)-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 % or 100 % RH. Ethylene promoted the transpiration of stem segments at 30 % RH. but not at 100% RH, while GA(3) had little effect on transpiration at either 30% or 100% RH. We propose that the absence of ethylene-induced internodal elongation at low RH is due, at least in part, to ethylene-induced transpiration.