Study On The Effect Of Calcium And Zinc On Fruit Granulation And Lignin Metabolism Of ‘Harumi Tangor’

Citrus fruit granulation is a physiological phenomenon that is easy to occur in the late stage of fruit development or storage.At present,there is no systematic conclusion about the cause of citrus fruit granulation and control measures.In this study,’Harumi Tangor’was used as the test material.By spraying different concentrations of calcium alkoxide and zinc alkoxide,the effects of lignin content and the activity of key lignin enzymes（PAL,CAD,POD）in the sap of late fruit development were studied.And the relationship between granulation and lignin metabolism,the effects of different concentrations of calcium alkoxide and zinc alkoxide treatment on the mineral element content and fruit quality of’Harumi Tangor’and their relationship with granulation were discussed.The research results are as follows:1.The’Harumi Tangor’fruit began to granulate 240 days after flowering（fruit ripening period）,and the granulation degree of fruit gradually increased with the prolongation of fruit retention time.At 280 d after flowering,the fruits of different treatments showed granulation,but the granulation index of 0.2 g·L^-1 calcium sugar alcohol treatment was significantly lower than that of spraying clean water（CK）,of which 0.2 g·L^-1 calcium sugar alcohol combination 0.3 g·L^-1zinc alkoxide has the best treatment effect,the granulation index is only 0.05,and CK reaches 0.82.2.When the fruit changes color to maturity and then to fruit-holding,the saccharin lignin content showed a―falling-rising‖trend.The PAL and CAD activities of the sacculus cells were consistent with the changes in the saccharin lignin content.It showed a―rising-descending-rising‖trend;the combined treatment of 0.2 g·L^-1 calcium alkoxides could significantly reduce the content of lignin and its key enzyme activity in sap cells,and its lignin content decreased by 45.74%compared with CK at 280 days after anthesis～49.81%,PAL,CAD and POD activities were 39.34%～47.49%,35.82%～46.80%and40.56%～54.93%lower than CK,respectively.Correlation analysis showed that the fruit granulation index was significantly positively correlated with lignin content and its key enzyme activities.The combined treatment of 0.2 g·L^-1calcium alkoxide decreased the fruit granulation index by inhibiting lignin synthesis.3.Correlation analysis showed that the contents of Ca,Mg,Zn and B in the peel and the contents of Ca,Zn and B in the juice cell were negatively correlated with the granulation index,and the contents of K and Cu in the peel were positively correlated with the granulation index of the fruit.The combined treatment of calcium and zinc can significantly increase the content of Ca,Zn,Mg,B in the peel and juice cells,and reduce the content of K,Cu in the peel and juice cells.By coordinating the balance between mineral elements,it can promote the normal development and growth of fruit.Reduce the incidence of fruit granulation.4.In the later stages of fruit development,the content of sugar components showed an overall upward trend,and the content of organic acids showed an overall downward trend.Principal component analysis showed that the fruit granulation index was positive with malic acid,fruit shape index,single fruit weight,lignin content,and peel thickness.Correlation,negative correlation with total acid,citric acid,quinic acid,fructose,V_C,TSS,sucrose,total sugar,glucose.By constructing a comprehensive evaluation model,0.2g·L^-1 calcium alkoxide combined with 0.3 g·L^-1zinc alkoxide had the highest score,indicating that 0.2 g·L^-1 calcium alkoxide combined with 0.3 g·L^-1zinc alkoxide The treatment has the best effect on improving the overall quality of the fruit.In summary,spraying 0.2 g·L^-1 calcium sugar alcohol and 0.3 g·L^-1sugar alcohol zinc fertilizer in the fruit enlargement period（August,September）and color transformation period（October,November）can be effective decrease the activity of lignin and its key enzymes in the later stages of fruit development,adjust the content of mineral elements in the fruit,effectively control the occurrence of’Harumi Tangor’granulated fruit,and have a significant effect on the improvement of fruit quality.