Abstract
As factors inducing growth injury on plants under the high pH above 9, deficiencies of P, Fe, etc. and ammonia toxicity have been well documented. At the same time, occurrence of hydroxyl ion toxicity has been assumed frequently although evidence was lacking. Therefore, we investigated whether the hydroxyl ion toxicity occurs in rice and tomato in the range of pH 9-11. Result showed that the growth injury was induced by hydroxyl ion toxicity at the pH above 9. Then, mechanism of growth injury induced by hydroxyl ion toxicity were investigated. It was found that water absorption was inhibited within 12 hours above pH 9 (tomato) and pH 10 (rice). In addition, root elongation was inhibited during 8 days growth. These results demonstrate that hydroxyl ion toxicity exists in rice and tomato. However, MDH activity in the crude homogenates of leaves, stem and roots were not affected significantly.
