Various methods has been offered to determine the isoelectric point of protoplasm of living plant cells. Robbins (1923) maintained that not only the distilled water in which the tissue is immersed, did change the pH to agree with the isoelectric point of the tissue, but also the pH of the lower concentrated buffer solution moved toward the isoelectric point of the tissue for a few hours. Youden and Denny (1926), on the contrary, found that it is the substances which leached out of plant tissues when soaked in the buffer solutions that mainly determine the change in the pH of the solutions, and it is not the ion sbsorption from the solutions by the insoluble amphoteric substances of the ptotoplasm. Tissue soaked in distilled water gave solution of the equal pH value with the buffer solution that was not materially changed in pH when the tissue was soaked in it. Most of the effect upon the buffer by the tissue, but, they manitain that it was caused by substances leached into the buffer out of the tissue. The present writer, considers that it is impossible to expect the correct value of the isoelectric point of the protoplasm by the presence of the acid equilibrium (Robbins effect), from the reason of the difficulty for the surrounding water to diffuse into the intercellularspace of the leaf tissue. On the other hand, the pH of the distilled water. decreased due to the dissolved carbon dioxid generated through the respiration of the tissue. In the present investigation, the isoelectric point of various crop plants were determined by the acid aggulutination and the dye absorption methods, the result of which was summarized as follows : 1. The imbibiting capacity of the potato tuber tissue showed the minimum value in the pH of buffer solution which agreed with the isoelectrie point of the tissue. 2. When the germinating percentage of pollens of the upland-rice and that of the seed of the paddy-rice plants were minimum, the pH of the buffer solution agrees fairly well isoelectricpoints of these organs. 3. The streaming of the protoplasm, in the root hair of wheat received toxic effects at acidic acid side of the isoelectric point when acid dyes were added to the various pH of buffer solutions and likewise at alkali side by basic dyes. 4. The isoelectric points of protoplasm of barley and wheat plants changed at various growing periods. Therefore, the crop plants are not to have constant specific value of the isoelectric points.
