Growth injury induced by high pH in rice and tomato


K. HIGUCHI, Laboratory of Plant Production Chemistry, Department of Applied Biological Chemistry, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan. Email:


An extremely high pH, above 10, can occur in sodic soils and even in saline soils after heavy rainfall. The indirect and adverse effects on plant growth that are induced by a high soil pH have been well clarified and include nutritional disorders such as P, Fe and Zn deficiencies and NH3 and HCO3 toxicities. However, studies of the growth injuries induced by the high pH itself are quite limited. We conducted studies to clarify the effect of a high pH on the growth of rice and tomato using a solution culture system developed to eliminate nutrient deficiencies and NH3 and HCO3 toxicities. Although the P, Fe and Zn contents in the shoots were at a sufficiently high level, growth of the tomato and rice was markedly reduced by the high pH conditions (at pH 10 and 11). Our results show the existence of growth injuries in higher plants, induced by a pH above 10. Inhibition of root elongation might be the primary growth disturbance induced by the direct adverse effect of the high pH.