Anatomical and histochemical studies of separation process on the juncture between calyx and fruit tissues on Japanese persimmon fruits

In this study, the abscission process was investigated by applying ethephon to mature harvested ‘Hiratanenashi’ fruit. Anatomical study indicated that abscission zone cells developed between in the calyx and fruit tissues (hereinafter referred to as “calyx-fruit tissue”). The abscission zone was composed of 6 to 10 rows with small and flat shaped cells. At the distal side, the cells were elongated. They were usually 2 to 3 cells in width, and found only on distal side. As ripening stage proceeded, they continued to enlarge, and cavities were formed. And fruit abscised at last. Stained with ruthenium red to detect pectin materials at the calyx-fruit tissue showed red color (positive), but not stained in red (negative) in elongated cell walls. Stained with zinc chloride to detect cellulose, it was observed that cell walls not stained in blue (negative) compared to the adjacent tissue cells. Stained with IKI to detect starch grains, elongated cells not stained in black (negative) were shown. These results indicated that chemical changes in the cell walls of the calyx-fruit tissue accompany structural changes in the corresponding cells. Fruit abscission in Japanese persimmon occurred by dissolution and breakdown of the middle-lamella of the elongated cell walls. This study suggests that enlarged cells in distal side of the abscission zone may act as ethylene target cells.