Control of Dissolved Oxygen Concentration in Deep Hydroponic Culture of Spinach Using Pressurized Oxygen Gas.

Abstract

Spinach (Spinacia oleracea L., cv. Okame) growth experiments were carried out to study the effect of dissolved oxygen (DO) concentration on growth in a deep hydroponic culture. Pure, pressurized, 02 and N2 gases were supplied to the hydroponic system for precise DO control. This system made it easy to increase the DO concentration beyond the maximal (or saturation) concentration possible when bubbling air into water. Fifteen-days-old spinach seedlings were grown for 7 days under various DO concentrations at solution temperatures of 25, 30 and 35 • Ž. For each temperature, three DO concentrations were tested : super-saturated (11-12 mg /-1), saturated(control, 7-8), and sub-saturated (2-4.5). Neither root damage nor delay in shoot growth was observed at any of the super-saturated DO concentrations for solution tempera-tures of 25 and 30 • Ž. Root dry weight at super-saturated DO concentration was approximately