Abstract
1. In order to make clear the physiological significance of the Eh value of the tissue fluid of the rice plant, we have made a study on the relation between the contents of ascorbic acid and glutathione in plant and the Eh value. 2. Ascorbic acid was determined by indophenol method. Glutathione was estimated by subtracting the amount of iodine equivalent to ascorbic acid from the total amount of iodine consumed by 2 % HPO3 solution of the tissue fluid. 3. Large amounts of both ascorbic acid and glutathione are contained in the leaves of the rice and the ascorbic acid exists mainly in the reduced form and the glutathione in the oxidized form 4. The ratio of the reduced form to total ascorbic acid (ASA/TA) rises while the Eh value lowers in the order leaf blade, leaf sheath, stem and root. 5. The ratio (ASA/TA) and Eh value in leaves show reverse trends with each other regarding to diurnal change and effect of shading. 6. The descend of the Eh value which occurs under such abnormal conditions as the deficiency of Mn, Mg, K or P and excess of N, seems to be closely connected with the increase of the ratio of reduced form to total ascorbic acid and/or similar change in glutathione. 7. From these results it is evident that the Eh value has a close relationship with the ratio of reduced form to total ascorbic acid and glutathione.
