Anatomical observations of anthocyanin rich cells in apple skins

Anatomical observations of anthocyanin rich cells in 'Fuji' apple skins were carried out by light microscopy and electron microscopy. Apple skins with fully developed red color had more layers of anthocyanin-containing epidermal cells than those of green skins. The density of anthocyanin was high in cells of the outer layer of the fruit skins and gradually decreased inward to the flesh. Anthocyanins were frequently found in clusters or in agglomerations that were round in the epidermal cells of the red skins. They accumulated in the inner side of developed vacuoles. Transmission and scanning electron microscopy revealed that the shapes of anthocyanins were cluster style, indeterminable forms, or complete spheres. Anthocyanin seemed to be synthesized around the tonoplast and condensed on the inward side of the vacuole. There was no distinct envelope membrane on the anthocyanin granule in the vacuoles of apple skin cells.