Effects Of Exogenous Calcium And Magnesium On Leaf Senescence In Fruiting Nodes And Yield And Quality Of Fruits Of Muskmelon

In this research, muskmelon cultivar “Yingchun (F1)” was used to carry out theexperiment. At first, the mechanism of the leaf senescence in fruiting nodes was studyed.The photosynthetic indexes, such as chlorophyll contents, net photosynthetic rate andchlorophyll fluorescence parameters, and the physiological indexes, such as solublecontend, MDA content and antioxidant enzyme system of the leaves in fruiting nodes andthe adjacent leaves in lord tendril and side branches were measured. The Ca and Mgcontents of the three kinds of leaves were measured too. Then in order to study the effectsof exogenous calcium and magnesium on leaf senescence in fruiting nodes and yield andquality of fruits of muskmelon, three different spray concentrations of calcium nitrate andmagnesium sulfate were tested at the bearing-fruit flowering stage. The photosyntheticindexes, physiological indexes, Ca and Mg contents, plot yield and quality of fruit weremeasured. The major findings were summarized as follows:1. During the process of fruit growth and development, compared with the adjacentleaves in lord tendril, the Ca and Mg contents of the leaves in fruiting nodes reducedsignificantly. In the latter stage of leaves growth, the Ca and Mg contents of the leaves infruiting nodes reduced significantly than the adjacent leaves in side branches. Comparedwith the adjacent leaves, the chlorophyll contents, net photosynthetic rate, soluble proteincontent, Fv/Fm, ΦPSⅡ, ETR of the leaves in fruiting nodes reduced significantly too. TheFo, MDA content, O2·-production rate of the leaves in fruiting nodes increasedsignificantly. The results show that the main reason for the leaf senescence is caused bylibrary source and nutrient compettion between the fruits and leaves in fruiting nodes. Thedeficiency of Ca and Mg contents, reduced chlorophyll and soluble protein contents, andlower antioxidant enzyme activitives accelerated the leaf senescence of the fruiting node.2. During the process of fruit growth and development, spraying25,40mmol/LCa(NO3)2can increase the Ca and Mg contents, chlorophyll contents, net photosyntheticrate, soluble protein content, Fv/Fm, ΦPSⅡ, ETR, enhance the activities of SOD, POD,CAT and decrease the Fo, MDA content and O2·-production rate of the leaves in fruitingnodes.25mmol/L Ca(NO3)2treatment was proved the best.40mmol/L Ca(NO3)2inhibitedthe autioxidant enzyme activities, increased the MDA content and O2·-production rate, and caused the leaf senescence ealier.3. Different Mg(SO4)2concentrations treatments had different effects on leaves infruiting nodes. Compared with the CK, both the20and40mmol/L Mg(SO4)2treatmentscan increase chlorophyll contents, net photosynthetic rate, soluble protein content, Fv/Fm,ΦPSⅡ, ETR, and decrease the Fo, MDA content and O2·-production, and increase theactivities of SOD, POD, CAT.40mmol/L Mg(SO4)2was be proved the best. All of20、40、60mmol/L treatments can increased the Mg content,but can’t increased the Ca content.4. Both the yield and quality would be influenced by spraying different concentrationsof Ca(NO3)2and Mg(SO4)2.25mmol/L Ca(NO3)2can increase slobule solid, Vc, slobuleprotein, sobule sugar contents and plot yield, decreased the titrarable acid.40mmol/LMg(SO4)2can also increase slobule solid, Vc, slobule protein and sobule sugarcontents,decreased the titrarable acid. But different concentrations Mg(SO4)2had nosignificant different on plot yield.