Study on dynamics of calcium pectate,calcium oxalate and pectin during citrus fruit development

An experiment was conducted to study the changes in concentrations of calcium(Ca) pectate,Ca oxalate and pectin in the ovary(fruitlet),rind and pulp of the two cultivars,8-year-old parthenocarpic Kamei Satsuma mandarin (Citrus unshiu Marc.) and self-pollinated Egan 1 tangerine(Citrus.reticulata Blanco) grafted on trifoliate orange rootstock(Poncirus trifoliata Raf.),throughout fruit development in this study.This study aimed to identify the effects of fertilization on different forms of Ca and pectin in the ovary(fruitlet) and structural parts of fruit and their possible relationship with fruit development of the two different cultivars.Ca and pectin were measured by an atomic absorption spectrophotometer and carbazole-H_2SO_4 spectrometry,respectively.The results showed as follows: 1) Similarly declining trends of Ca pectate concentrations were observed in the ovary(fruitlet) of both cultivars,while dynamics of Ca oxalate concentrations were inverse.Concentrations of Ca oxalate decreased in the ovary(fruitlet) of Kamei after flowering,whereas that of Egan 1 presented significantly increasing trend.Relatively high concentrations of Ca pectate,Ca oxalate and pectin were detected in the ovary(fruitlet) of Egan 1.2) During fruit enlargement,concentrations of Ca pectate(increased) significantly in the rind and pulp of both cultivars,and concentrations of Ca oxalate in the rind of both were relatively high although some fluctuations were found.However,remarkably decreasing trends were found for Ca oxalate in the pulp.3) Water soluble pectin concentrations increased markedly in the rind and pulp of both cultivars,and protopectin concentrations were relatively high during fruit enlargement.Both cultivars presented obviously declining trends during late fruit enlargement.The relationship between changes in concentrations of Ca pectate,Ca oxalate,Water soluble pectin and proto-pectin in the ovary(fruitlet) and structural parts of fruit(rind and pulp) and fruit development was discussed herein as well.