The activity analysis for sugar-metabolizing related enzymes in 3 kinds of navel orange fruits

【Objective】 This research studied the sugar concentrations and changes in enzyme activities during the development of 3 kinds of navel orange fruits.The key enzyme which influences the diversity of sugar content and the period when it effects were discussed in order to provide the oretical basis for quality improvement of havel orange fruit.【Method】 Using fruits of Robertson Navel orange,Newhall Navel orange and Harvest Navel orange as experimental materials,samples were taken every 15 days from 60 days after bloom for 11 times in total.Sugar concentrations and the enzyme activities of NI(Neutral invertase),AI(Acid invertase),SS(Sucrose synthase)and SPS(Sucrose phosphate synthase)were investigated before being compared with other kinds.【Result】 From 90 days after bloom,the significant diversity of sugar contents in different kinds of naval orange fruit was mainly caused by the fact that the velocities of sugar accumulation in Newhall Navel orange and Harvest Navel orange fruits were faster than Robertson Navel orange.So the sugar content in the Newhall Naval orange and Harvest Navel orange fruits respectively achieve very significant difference and significant difference.There was no relation between the catabolic activities of sucrose enzymes and between sucrose concentrations of different citrus fruits.But since 90 days after bloom,the activities of SPS and SS(Synthesis direction)in the Newhall Navel orange and Harvest Navel orange fruits were very significant different and significant different than Robertson Navel orange,respectively.【Conclusion】 It is suggested that the difference of sugar contents in different varieties is mainly determined by SPS and SS(synthetic direction).They influence sugar contents in different varieties by promoting sugar synthesis in the mid-and late-stage of fruit development.