| In order to find the best calcium supplementation measures for ’ Nagafu 2’ apples,so as to reduce the occurrence of bitter pit effectively,and provide theoretical basis for fertilization.In Gangdi Village,Neiqiu County,Xingtai City,Hebei Province,15-year-old’Nagafu 2’ apple trees were used as materials by field investigation and laboratory analysis methods to study the effects of different amounts and times of calcium fertilizers by trunk infusion on antioxidant enzyme activity,MDA content,CaM content,mineral element content of different organs(leaves,branches,fruits),fruit quality,and incidence of bitter pit.To explore the characteristics of calcium absorption and distribution in apples and their influencing factors,as well as its relationship with the occurrence of apple bitter pit.The main results were as follows:(1)The contents of Ca and Mg in leaves,branches and fruits treated with calcium fertilizer by trunk infusion were significantly higher than those of the control(CK),while the N,P and K contents were significantly lower than the CK.In each calcium fertilizer infusion treatment,the average N content of leaves,branches and fruits treated by 9g/plant for 3 times reached the lowest values,which were 19.81g/kg,8.91g/kg and 6.40g/kg respectively.The average contents of P in leaves and branches treated by 9g/plant for 3 times reached the lowest values,which were 2.12g/kg and 0.73g/kg,respectively.The average contents of P in fruits treated twice by 9g/plant reached the lowest value(1.02g/kg).The average content of K in leaves treated by 9g/plant for 3 times reached the lowest value,which was 16.41 g/kg.The average K content of 12g/plant was 6.14g/kg.The average content of K in fruits of CK reached the lowest value,12.96g/kg.The average Ca contents in leaves,branches and fruits treated by 9g/plant for 3 times reached the highest values,which were 13.75g/kg,9.80g/kg and 1.42g/kg,respectively.The average contents of Mg in leaves and branches treated by 12g/plant for 1 time reached the highest values,which were 4.34g/kg and 2.83g/kg,respectively.The average content of Mg in fruits treated by 9g/plant for 3 times reached the highest value,which was 0.67g/kg.The N/Ca mean values of leaves,branches and fruits treated by 9g/plant for 3 times reached the lowest,which were 1.93,0.95 and 4.48,respectively.(2)The increase of Ca content in the tree would increase the content of calmodulin(CaM).In the treatment of calcium infusion,the mean CaM contents of leaves and fruits treated by 9g/plant for 3 times reached the highest values,which were 156.27μg/g and 85.59μg/g respectively;the mean CaM contents of branches treated by 9g/plant for 1 time reached the highest value,128.81μg/g.At the same time,calcium ions could regulate the activity of antioxidant enzymes,and the activities of 3 protective enzymes(SOD,POD,CAT)in plants were significantly increased,while the contents of MDA were significantly decreased.In each fertilization treatment,the mean SOD activities of leaves and branches treated by 9g/plant for 3 times reached the maximum values,which were 16.68U·g-1·min-1 and 20.53U·g-1·min-1 respectively.The average SOD activity of the fruits treated by 9g/plant for 2 times reached the maximum value,which was 8.63U·g-1·min-1.The average activities of POD and CAT in leaves,branches and fruits treated by 9g/plant for 3 times reached the maximum.The mean MDA content of leaves treated by 6g/plant for 3 times reached the lowest value,7.81μmol·g-1FW;the mean MDA contents of branches and fruits treated by 9g/plant for 3 times reached the lowest values,which were 7.34 μmol·g-1FW,and 1.07 μmol·g-1FW.(3)The content of mineral nutrient elements in different parts of apple tree is different,among which the average content of N element varies from 12.89 to 35.09g/kg in the fruit branch leaves,from 10.95 to 32.49g/kg in the vegetative branch leaves,from 10.82 to 12.78g/kg in the fruit branches,from 7.10 to 10.24g/kg in the vegetative branches and from 6.27 to 10.17g/kg in the fruits,It can be concluded that the distribution rule of N element is:fruit branch leaves>vegetative branch leaves>fruit branches>vegetative branches>fruits;the average content of P element varies from 1.43 to 3.93g/kg in the fruit branch leaves,from 1.43 to 3.82g/kg in the vegetative branch leaves,from 0.91 to 1.34g/kg in the fruit branches,from 0.51 to 1.02g/kg in the vegetative branches and from 0.91 to 1.52g/kg in the fruits,It can be concluded that the distribution rule of p element is:fruit branch leaves>vegetative branch leaves>fruits>fruit branches>vegetative branches;the average content of K element varies from 15.13 to 21.60g/kg in the fruit branch leaves,from 13.52 to 23.08g/kg in the vegetative branch leaves,from 5.65 to 10.91g/kg in the fruit branches,from 4.07 to 9.55g/kg in the vegetative branches and from 12.18 to 15.58g/kg in the fruits,It can be concluded that the distribution rule of K element is:fruit branch leaves>vegetative branch leaves>fruits>fruit branches>vegetative branches;the average content of Ca element varies from 7.59 to 19.73g/kg in the fruit branch leaves,from 5.89 to 16.13g/kg in the vegetative branch leaves,from 5.53 to 10.92g/kg in the fruit branches,from 4.16 to 8.36g/kg in the vegetative branches and from 0.76 to 1.24g/kg in the fruits,It can be concluded that the distribution rule of Ca element is:fruit branch leaves>vegetative branch leaves>fruit branches>vegetative branches>fruits;the average content of Mg element varies from 1.58 to 7.62g/kg in the fruit branch leaves,from 1.05 to 7.13g/kg in the vegetative branch leaves,from 1.24 to 4.91g/kg in the fruit branches,from 0.88 to 3.21g/kg in the vegetative branches and from 0.37 to 0.69g/kg in the fruits,It can be concluded that the distribution rule of Mg element is:fruit branch leaves>vegetative branch leaives>fruit branches>vegetative branches>fruits.(4)Calcium fertilizer infusion could reduce the incidence of bitter pit and improve fruit quality.The fruit weight and soluble solid content of each fertilization treatment were significantly higher than that of the CK,and the fruit weight of the treatments of 12g/plant for 3 times was the largest,229.5g.The total sugar content of 9g/plant for 3 times was the highest,12.88%.The titratable acid contents of 9g/plant for 3 times and 12g/plant for 3 times were significantly lower than the other treatments,both were 0.32%.There was no significant difference in the sugar-acid ratio between 9g/plant and 12g/plant for 3 times,but they were significantly higher than the other treatments,and the highest value was 40.68.The incidence of bitter pit treated by fertilization was significantly lower than that of CK,and the incidence of 9g/plant for 3 times was the lowest,that was 18%.(5)The incidence of bitter pit of fruit was extremely significant positive correlated with N,P contents,and N/Ca values,and the average correlation coefficients were 0.78,0.88,and 0.88 respectively,and extremely significant negative correlated with Ca and Mg contents,and the average correlation coefficients were-0.84 and-0.83 respectively;extremely significant negative correlated with SOD,POD,CAT activities,with the average correlation coefficients were-0.84,-0.81,-0.85,respectively;extremely significant positive correlated with MDA content,and the average correlation coefficient was 0.84;significant negative correlated with soluble solids,total sugar content,sugar acid ratio,and the average correlation coefficients were-0.78,-0.64,and-0.74,respectively;significant positive correlated with the titratable acid,and the average correlation coefficient was 0.67.(6)The fuzzy mathematical membership function method was used to comprehensively evaluate the effect of calcium fertilizers by trunk infusion under different treatments using multiple indicators.The membership function value of 9g/plant for 3 times was the largest,which was 0.528.Therefore,the effect of 9g/plant 3 times application treatment was the best,which could be applied to the production fertilization of bitter pit control. |
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