Water adhered on the fruit surface during maturation period is the main cause of apricot cracking

摘要

Cracking of apricots has become the major bottleneck of apricot industrial development. In this study, breakable 'Katy' apricot was used as the test material, and magenta tracer, paraffin section, trypan blue staining, and TUNEL detection were used toexamine the mechanism of cracking in 'Katy' apricot. The results indicated that, during early development of the apricot fruit, some vascular bundles of the stalk were connected directly to the stone, with other bundles connected to the flesh. With stone lignification, the distance between the stalk and stone decreased. At the maturity stage, the stalk was almost connected directly to the stone. Paraffin section showed that, during the development of apricot, the vessels of the stalk were kept unobstructed, and there was no obvious degradation, breakage, or blockage. In the magenta tracer experiment, we found that the magenta solution could be transported easily into the fruit in the early period of fruit development, but it was hardly seen in partlyand fully red-stage fruit. Trypan blue staining and TUNEL detection confirmed that there was obvious apoptosis and death in the peel during the development of apricots, especially at the later stage, when skin cells showed partial mortality and fruit rust (spots produced by external stimuli) in parts of the cell where increased death occurred. During the development of apricots, a 'gap' appeared because of pubescence degeneration, and some "gaps" were connected directly to the subepidermal cells, and the layers of epidermal cells decreased during the early stage. These results showed that, at the later stage of apricot development, the partial mortality of epidermal cells, pubescence degeneration, and a decrease in the number of epidermal cells were the major causes of apricot cracking.