Dissolved O2 concentration ([O2]) in nutrient solution was controlled at 0.01, 0.10 and 0.20 mM with accuracy of ±0.005 mM in a newly developed hydroponic system, and the effects of [O2] on water uptake and growth of cucumber plants (Cucumis sativus L.) were analyzed. For evaluating water uptake rate under the control of [O2] water flux at the stem base was measured on-line with ±5% in accuracy, 1 mg s-1 in resolution and 1 min in time constant by heat flux control (HFC) method. Water uptake rate was drastically increased by lighting to the plant at each [O2] and water uptake per day was depressed in proportion to decrease in [O2]. In the plants grown for 10 days, leaf area, fresh weight and dry weight of leaves decreased at lower [O2], while stem length and number of leaves were scarcely affected. These facts suggest that membrane permeability of root cells reduces at lower [O 2] through respiration-dependent processes, and growth is inhibited through leaf turgor loss caused by the depressed water uptake of roots in O 2-deficient nutrient solution in hydroponics.
All Science Journal Classification (ASJC) codes