Effects Of Grafting On Low-temperature Tolerance And Photosynthate Translocation In Melon Seedlings

Melons are sensitive to cold,which has adversely affected the cultivation of melons in the north during the fall and winter.One of the effective methods to solve this problem is grafting by cold-resistant rootstock.In this experiment,we use‘TZ-1',‘TZ-2',‘QY-1',‘QY-B25',‘SZ-1',‘LG-1',‘373*365'and‘373*367'for the rootstocks,‘JY-5'for the scion and has evaluated the low-temperature resistance of these eight grafted union under15?/10?,and selected strong low-temperature resistance rootstocks-‘SZ-1'.Under the conditions of 15?/10?,we study the physiological characteristics,antioxidant enzyme activities,expression of low-temperature resistance related genes,photosynthetic capacity and mineral nutrient content of the grafted unions.This study also studied the translocation of photosynthetic products for grafted unions.the results of the study are as follows:1.Under 15?/10?,the average relative degree of relative germination rate,relative germination potential,relative germination index,relative dry fresh weight and relative radicle length of these rootstocks is different,and the‘TZ-1'is the highest,followed by‘SZ-1';‘373*365'and‘373*367'are smaller than other stocks,‘LG-1',‘QY-1',‘QY-B25'and‘TZ-2'is no difference.The relative electrolyte permeability and the content of MDA for grafted unions‘SZ-1'and‘LG-1'are significantly lower than‘373*365'and‘373*367',while the content of soluble sugars is significantly higher than other four grafted unions;the content of soluble protein in leaves of‘SZ-1'is significantly higher than other grafted unions.2.Under 15?/10?,the relative electrolyte permeability and the content of MDA in the leaves of self seedlings and grafted seedlings are significantly increased,and self seedlings are more larger.The MDA content of self seedlings and grafted seedlings reached the maximum at 24h,which is 2.9 and 1.7 times compared with that before treatment.The content of soluble sugar and proline increased significantly.The content of soluble protein for self seedlings are decreased first and then increased,and the grafted seedlings are significantly increased.The grafted seedlings are significantly higher than the self seedlings about the content of soluble sugar,soluble protein and proline.3.Under 15?/10?,the activity of Cm-SOD in the leaves of self seedlings and grafted seedlings significantly increased,and the activity of Cm-POD decreased first and then increased.The activity of Cm-SOD and Cm-POD in grafted seedlings is higher than that of self seedlings;The relative expression of Cm-Mn-SOD,Cm-CAT,Cm-ERF and Cm-DREB1are significantly increased,and all of these relative expression of grafted seedlings are significantly higher than that of self seedlings.The relative expression levels of Cm-Mn-SOD and Cm-DREB1 peaked at 36 h,while Cm-CAT and Cm-ERF showed an increasing trend and peaked at 72h.4.Under 15?/10?,the Fv/Fm values of the self seedlings and grafted seedlings are significantly decreased,but the grafted seedlings have a smaller decrease;the contents of N,K and Mg in the ground parts and underground parts,as well as the content of P in the ground parts and the content of Ca in the underground parts rapidly decreased,and there is no significant difference for the content of Ca.In addition,the remaining indicators of grafted seedlings are significantly higher than that of self seedlings.5.¹³C is detected in P1?the first part?,P2?the second part?,P3?the third part?,and P4?the fourth part?in self seedlings and grafted seedlings after two hour of ¹³C isotope tracing,and the abundance of ¹³C in P1 and P4 for grafted seedlings is significantly higher than that of self seedlings,and the abundance of ¹³C in P2 is significant low than self seedlings.¹³C is detected in five parts of self seedlings and grafted seedlings after ¹³C isotope tracing.Except the abundance of ¹³C in P2 for self seedlings is significantly higher than that of grafted seedlings,the others is not significant.