Abstract
For analyzing the effect of dissolved O2 concentration on root water uptake in hydroponics, the stem base water flux in cucumber plants (Cucumis sativus L.) was measured by heat flux control method (HFC) in “a” newly developed system for controlling dissolved O2 concentration. At an air temperature of 25°C, a relative humidity of 70%, a PPFD of 300μmol m-2 s-1 (a photoperiod of 12 h) and a root temperature of 25°C, dissolved O2 concentration was controlled at set values of 0.01, 0.10 and 0.20 mM with an accuracy of ±0.005 mM. At each dissolved O2 concentration, the water uptake rate drastically increased by lighting the plant, and water uptake reduced in proportion to decrease in dissolved O2 concentration: Water uptakes per day at 0.20, 0.10 and 0.01 mM were 235, 186 and 164 g, respectively. This fact suggests that root water uptake in hydroponics is depressed at lower dissolved O2 concentrations by change in membrane permeability of root cells through respiration-dependent processes.
