Prevention of peel splitting of loquat

1.通过光学显微镜和扫描电子显微镜观察到，对于“茂木”和“长崎-Wase”，来自奄美大岛的水果容易果皮开裂，比来自樽水的水果几乎不开裂，具有更大的皮层细胞。大岛的果实在交叉生长停止后也继续横向生长。仅纵向且仅在剥离处发生裂开，未延伸至皮质区域。结果表明，果皮中4-6层细胞的分裂是由于内部皮层细胞膨压的增加.大岛果实的果皮抗拉强度较弱，易开裂。剖分果实的横向强度远小于纵向强度.裂果的成熟期较晚，表现为果实着色度和锤度较高，酸度较低.对果园的调查表明，施肥、土壤管理、排水、病虫害管理等栽培措施较好的果园，裂果较少。土壤理化性质的改善有利于减少劈裂的发生和严重程度。塑料屋顶下的树木很少发生裂果.这些结果表明，果实成熟期根系吸水量的迅速增加，导致皮层细胞体积迅速增大，膨压增大，当果皮强度不足以抵抗膨压时，会引起果皮开裂。施用钙剂虽然被认为是强化果皮，而生长调节剂控制果实生长，却未能控制裂果的发生。在土壤水分管理、果皮抗拉力强的品种选择、成熟度判断方法等方面还有待进一步研究。

1. It was observed by light and scanning electron microscopy that for both 'Mogi' and 'Nagasaki-Wase', fruits from Amami Oshima Island which are prone to peel splitting, had the larger cortex cells than those from Tarumizu which scarcely show splitting. Fruits from Oshima also continued transvese growth after cross growth ceased. Splitting occurred only longitudinally and only at peel, not extending to cortex area. It was observerd that 4-6 layrs of cells in the peel split by an increase of turgor pressure of inside cortex cells.2. Strength of resistance to pulling of peel was considerably weaker in the fruits from Oshima island which are more prone to splitting. Split fruit showed much weaker strength cross-wise compared to that of longitudinal direction.3. Split fruits seemed to be more advanced stage of ripening as shown by higher coloration and brix and lower acidity.4. Survey of growers' orchards revealed that less splitting occurred in the orchards of which cultural practices were better in terms of fertilization and soil management, drainage practice and pest and desease management. Improvement of soil physical and chemical properties tended to decrease the occurrence and severity of splitting. Trees under plastic roof showed less occurrence of splitting.5. These reults strongly suggest that rapid increase of absorption of water from roots during fruit maturation periods resulted in rapid increase in the size of cortex cells and the turgor pressure of these cells also increased, which in turn caused peel splitting if the peel strength was not strong enough to resist the pressure. Application of calcium which is thought to strengthen the peel, and growth regulators to control fruit growth, failed to control the occurrence of splitting. Further research is needed to find out better soil water management, selection of cultivars, the peel of which is stronger and resistant to pulling force, and proper methods of judging ripening strage.