温州ミカンの浮皮に関する研究(第2報)

Abstract

Morphological and anatomical changes of the rind cells were investigated throughout the development of satsuma mandarin fruit (Citrus unshiu MARC.). The cellulase activity of the rind tissue was also determined in relation to the cell enlargement.1. Cell division almost ceased 20 days after full bloom in the inner layer of the albedo, 30 days in the outer albedo and 40 days in the mid flavedo, when the fruit diameters were about 10, 20 and 30mm, respectively.2. In the albedo tissue, pectic substances began to accumulate in the intercellular spaces when cell enlargement started after the cell division had ceased. The accumulation of pectic substances increased gradualy during the development of rind. The cell wall where the pectic substances accumulated was depressed slightly toward the inside, and the primary protuberances of the cells appeared simultaneously on the portion where cells adhered closely the adjacent ones.3. With a further expansion of epidermis, the protuberances of albedo cells were lengthened in the periclinal direction. Accordingly, the albedo cells resembled a starfish or spider in shape. In radial section of the rind, the protuberances were arranged approximately in parallel to the fruit surface. Thus, the solid albedo tissues in the younger stage were transformed to somewhat spongy tissues including large intercellular spaces. The growth of cells in the flavedo followed approximately the same process as that of the albedo. The aging of flavedo, however, was more delayed than that of albedo.4. The water content of albedo tissue decreased since at the later stage of fruit development the intercellular spaces of albedo cells enlarged and thus the surface area exposed to the ambient atmosphere was increased. In the flavedo, however, the water content remained almost constant.5. The cellulase activity of the albedo tissue was reduced markedly as the fruit came near the stage of maturity. On the other hand, its activity in the flavedo was reduced slightly.