Abstract
The authors examined the path of movement of phosphate after having been absorbed through leaf surface of tomato directly by the use of radioautography. Tomato plant, about 30 cm high, was applied on one of the leaves with ca 1/50 M potassium dihydrogen phosphate containing P-32 (120 micro curie/ml). After 24 hours of the application, the petiole of the applied leaf and the stalk were sampled. In the stalk, decisions were made at two positions where are 1 cm above and below the attaching point of the petiole. Each section, 50μ thick, was pressed between filter paper and cellophane (lOμ thick) by hot iron. On this dried preparate, Fuji stripping film ET-2E was decked with the intermediation of the cellophane, then they were hold between two slide-glass, covered with black paper and then exposed for 20 days in an desiccator. By this procedure, watersoluble phosphates contained in the preparate would be able to remain as they are. Radio-autography thus prepared are shown in Plate 2,4 and 6. Compared each of them with Plate l, 3 and 5 respectively, the following results may be withdrawn : l) Foliar absorbed phosphate (P-32) is accumulated first into vascular bandle. At petiole it was found almost in phloem tissue, then moved downward to the stalk. 2) At the petiole it was found that P-32 was also accumulated in outer layer of cortex and epidermis in addition to vascular bandle. 3) P-32 which had been introduced into stalk, moved downward chiefly through phloem, however a little P-32 was found in xylem. 4) At upper part of stalk, on the contrary, much P-32 was found in xylem, especially in primary vessels, rather than in phloem.
