Research on the Pit Splitting Mechanism in Peach and a Trial to Reduce the Split-pit-induced Fruit Drop before Harvesting

日本的水果种植者倾向于根据消费者的需求生产大尺寸的水果。但是，促进果实生长的处理也促进了裂坑和落果。前人的研究结果如下：1)裂坑主要是由果肉的拉力引起的，拉力主要发生在第II阶段。2)未成熟的种皮暴露在空气中后，迅速产生乙烯。3)在裂坑的常见情况下，裂隙局限在内果皮上，在果实成熟之前不会诱导种子产生空气，也不会释放乙烯，但成熟前会促进果实落果。虽然从第一阶段到第三阶段，石头的硬度有所增加，但在第二阶段，石头被估计为脆性和脆性。促进生长的试验区果肉的抗拉强度、塑性和杨氏模量比对照增加得更多。在果核内腔加压注入染料溶液使果核裂开时，随着果实的发育，裂果阻力随果实发育而增加，但第II期的抗裂力随生长促进而降低，且果径与果核阻力呈负相关。花蕾疏果更适合于大小较小、裂坑较少的果实生产，因为提早疏芽可促进剩余果肉的细胞分裂，确保果实在危险的第II期后生长良好。但值得注意的是，疏花区种子的胚囊经常变形。其中核DNA倍性水平异常。

Fruits growers in Japan tend to produce big size fruits as dictated by consumer's demand. But, the treatments to promote the fruit growth also promote the split-pit and fruit drop. Previous results on the research are as follows; 1)Split-pit should be induced by the tensile force of flesh which pull sidewise the pit mainly during the period of stage II. 2)Immature seed coat drastically produces ethylene just after being exposed to air. 3)In common case of split-pit, in which the cracks are restricted in endocarp, no air is induced to seed and no ethylene is released until fruit maturation, but fruit drop is promoted before maturation.In this report, physical properties of peach fruits were investigated. Although hardiness of stone increased from stage I to stage III, the stone was estimated to be brittle and crisp during stage II. Tensile strength, plasticity and Young's modulus of the flesh in the growth promoted plot were more increased than those in the control. When pit was artificially split by injection of dye solution from the peduncle scar to the inner cavity of stone with increasing pressure, resistance force to rapture increased accompanying with the fruit development, but the values of those during stage II were statistically reduced by growth promotion, and a negative relationship between fruit diameter and the resistance force was observed.Flower bud thinning is more advisable for fruit production with better size and less split-pit, because earlier thinning may promote cell division of the remainder and secure the possibility of better fruit growth after the risky stage II. But, it is noticeable that embryo sacs of the seed in the plot of flower bud thinning were frequently deformed, in which abnormality of ploidy level by nuclear DNA was observed.