Abstract:【Objective】The purpose of this study was to reveal the phenological period, appearance, microstructure changes and the interaction between different European plum varieties in the fruit growth cycle, in order to grasp the pattern of growth and development of European plum fruit, provide scientific guidance for improving fruit quality.【Methods】Six European plum varieties were selected as experimental trees to dynamically monitor the changes of fruit Phenological period and appearance, the microstructure changes of fruit cells at different developmental stages were analyzed by paraffin microtomy method.【Results】The results showed that the fruit phenological period included the first expansion period, pollution period, second expansion period, color-changing period and mature period. The fruit development period of the six European plum varieties was about 121 d~160 d. The changes of fruit appearance morphological can be divided into four stages: rapid growth period (S1), slow growth period (S2), stable maturity period (S3) and physiological fruit drop period (S4). The changes of fruit microstructure showed that the epidermis of the exocarp was a single layer structure, and the shape was neatly square and rectangular. Epidermis, subepidermis, mesocarp and vascular bundle cells in S1 were small, concentrated and dense, the S2 cells increased and diffused, the S3 developed and improved gradually, the epidermis and mesocarp of S4 continued to be stable, while the subepidermis thickness became thinner and the vascular bundle phyllotoxin slightly degraded. Correlation analysis showed that there was a significant correlation between fruit cell morphological parameters and appearance morphological indexes.【Conclusion】This study revealed the pattern of fruit development and microstructure changes among six European plum varieties. It was found that the epidermis, subepidermis, mesocarp and vascular bundle cells expanded significantly in the early stage of S1~S4, and tended to be stable in the later stage, accompanied by thinning of subepidermis and slight degradation of vascular bundle phyllotoxin. The key to the growth and development of fruit appearance is closely related to the area, perimeter, longitudinal diameters, equatorial diameter and roundness of mesocarp cells, and the morphology of mesocarp cells also has a direct impact on the longitudinal diameters and equatorial diameter of exocarp cells. In order to provide an important reference for the regulation of fruit development process related cultivation methods and effective prevention and control of fruit cracking damage by observing the early phenological period of fruit and analyzing the changes of growth and development.
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