Ethylene enhances water transport in hypoxic aspen

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 muM 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.