Improve fruit quality and prolong storage time of Jincheng orange by calcium sprayed in growth period

Calcium (Ca), as an important nutrition, can regulate the physiological metabolic process and is closely related to fruit quality, the shelf life of fruit and physiological diseases during storage time. It is meaningful to study the relation of Ca nutrition and fruit quality and senescence for producing fruit with high quality, alleviating economic loss from rotten fruit and prolonging the fruit storage time. At present, there were some reports about Ca nutrition and fruit quality but many reported the effect of Ca on storage property of fruit by studying the respiration intensity and electric conductivity of fruits supplementing Ca solution on fruit during maturing stage or harvest time, few reported the effect of Ca on the inherent quality and the shelf life of fruits supplying Ca nutrition during fruit growing period. In order to make clear the effect of Ca nutrition sprayed on citrus trees in different growing periods on citrus fruit quality and senescence during storage time and propose comprehensive management measures for Ca nutrition of citrus orchards, the effect of Ca on fruit quality including vitamin C, total sugar, acid, total soluble solid (TSS), some enzymes and materials related to fruit senescence including peroxidase(POD), catalase(CAT), superoxide dismutase(SOD), polygalacturonase(PG), cellulose(CX), malonaldehyde(MDA), protopectin(PP) and soluble pectin(SP) were studied in this paper. The effects of Ca on quality and enzyme activities of citrus fruits were studied by spraying calcium nitrate in different growth periods on Beibei-447 Jincheng orange (Citrus sinensis Osbeck, Beibei-447 orange). The results showed that Ca mass fraction in citrus fruits increased significantly, the oxygenolysis of vitamin C was restrained, total soluble solid (TSS), the ratio of sugar and acid increased and the fruit quality were maintained during storage by spraying Ca on citrus trees in different growth periods. The activities of polygalacturonase (PG), cellulase (CX) and peroxidase (POD) of different Ca treatments decreased but those of superoxide dismutase (SOD), catalase (CAT) increased because of high Ca mass fraction in fruits. The structure of cell was protected and lipid peroxidation was alleviated so that the mass fraction of malonaldehyde (MDA) and soluble pectin decreased, the senescence of fruit was postponed and the fruit was eventually kept in good during storage. The best effect on prolonging storage time of citrus fruit was to spray Ca on citrus trees in young fruit period, then spraying Ca on citrus trees in fruit rapid growth period and the worst was in fruit mature period. Spraying Ca on citrus trees in young fruit period and fruit rapid growth period were important measures to keep citrus fruit in good quality during storage.