During the flowering stage of Wase satsuma mandarin, Citrus unshiu Marc. var. praecox Tanaka, the abscission layer formed at the junction of the base of the ovary and the filament or petal. The abscission layer was first evident one to three days after flowering. This layer was composed of 15 to 20 rows of cells in the constricted zone at the attachment points of filaments or petals and was first identified by its high affinity for iodine-potassium iodide. Cell separation occurred with

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... of the cell walls. The abscission of floral organs was preceded by the deposition of starch grains in each of the cells which formed the abscission zone. After this starch accumulation was complete, no additional starch was deposited in the cells during abscission. Cellular separation occurred within the starch layer itself, and the starch was present in cells on both sides of the separation layer following completion of abscission. Subsequently, starch gradually disappeared from the parenchyma cells adjacent to the abscission layer.