Abstract
Mobilization of storage reserves in Japanese chestnut fruit was observed by scanning electron microscope during the storage period. We stored chestnuts at −20, 2, 8 and 20°C to examine the effects of temperature on mobilization of reserves during 12-week period after harvest. At harvest (shedding stage), the cotyledonary parenchyma cells were filled with amyloplast (plastid containing a amount of substantial starch granules) and it’s amount was gradually increased from the center region (adaxial region) of the cotyledon to the outer region (abaxial region) of the cotyledon. As the storage period progressed, the number of amyloplast per cell was declined in fruit stored at 2, 8 and 20°C and the rate of decline differed at each storage temperatures. Namely, higher temperatures facilitated starch decomposition. This is thought to occur because the storage temperature affects the respiration rate and starch decomposition products provide substrates for respiration. In nuts stored at −20°C, mobilization of reserves was not recognized during the storage period. The rate of starch decomposition also differed among regions of the cotyledon. At the outer region of cotyledon, the rate of decomposition was high and the inner region was low. Corresponding to the high rate of starch decomposition, an abundance of cytoplasm was observed between and surface of the amyloplast. It is suggested that the amount of cytoplasm was related to starch decomposition activities.
