Plant Physiol, March 2002, Vol. 128, pp. 962-969

Ethylene Enhances Water Transport in Hypoxic Aspen¹

Department of Renewable Resources, 4-42 Earth Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2E3

Water transport was examined in solution culture grown seedlings of aspen (Populus tremuloides) after short-term exposures of roots to exogenous ethylene. Ethylene significantly increased stomatal conductance, root hydraulic conductivity (L_p), and root oxygen uptake in hypoxic seedlings. Aerated roots that were exposed to ethylene also showed enhanced L_p. An ethylene action inhibitor, silver thiosulphate, significantly reversed the enhancement of L_p by ethylene. A short-term exposure of excised roots to ethylene significantly enhanced the root water flow (Q_v), measured by pressurizing the roots at 0.3 MPa. The Q_v values in ethylene-treated roots declined significantly when 50 µM HgCl₂ was added to the root medium and this decline was reversed by the addition of 20 mM 2-mercaptoethanol. The results suggest that the response of Q_v to ethylene involves mercury-sensitive water channels and that root-absorbed ethylene enhanced water permeation through roots, resulting in an increase in root water transport and stomatal opening in hypoxic seedlings.