Effect Of Endogenous Hormones Metabolism On Pericarp Thickness Of Kiyomi Tangor In C.junos(sieb.) Tanaka Rootstock

This test takes the Citrus cv.‘Kiyomi tangor'trees grafted using Poncirus trifoliate?KT/PT?and Citrus junos?KT/CJ?rootstocks as the material at the same level of the management,witch with the basic consistent 8 years-old tree,the same tree vigor,tree potential and the tree loading.Based on dynamic growth curve,fruit peel thickness change law of the study,to explore the growth and development process,the endogenous hormones change,metabolic enzyme activity and its gene expression effect on the thickness of the fruit peel.The results are as follows:?1?The changes of the vertical and horizontal diameter growth and development curves of the two kinds of rootstocks grafted were almost synchronous,showing a generally parabolic curve.In the whole growth and development cycle,the transverse diameter of the fruit is bigger than the longitudinal diameter.The fruit was oblate.Vertical and horizontal diameter of KT/CJ are significantly larger than the KT/PT.What's more,the growth curve of the vertical diameter of the grafted fruit of the two kinds of rootstock showed the same trend of change with three peaks,while the growth of the horizontal diameter showed the trend of"high-low-high"growth.Vertical and horizontal growth of KT/CJ was greater than KT/PT in the early,and there was no significant difference in the later period.?2?The growth curve of pericarp thickness of two kinds of rootstocks showed the tendency of first increasing,then decreasing and then gradually changing.Moreover,the thickness of pericarp of KT/CJ was significantly larger than that of KT/PT,which was related to the higher contents of IAA,GA₃ and ZT in the peel of KT/CJ,and the changes of the contents were closely related to the net activities of the related metabolic enzymes.However,the changes of ABA content,related enzyme activity and gene expression,which were mainly responsible for the maturation of fruit at the later stagare,were not very relevant to the variation in the thickness of the pericarp.?3?During the 85-165 days after flowering,GA20ox,KO expression in the peel of KT/CJ showed a rising trend,and reached the peak,then decreased gradually.In the same period,the changes of GA20ox,KO content in the pericarp of KT/PT were relatively flat.However,the expression of CKX in KT/CJ was lower than that in KT/PT,which indicated that the differences in GA20ox,KO and CKX expression levels at this time period would affect the thickness of peel.It showed that the higher GA20ox,KO expression and the lower CKX expression in a certain range,the stronger the growth and development of pericarp,the thicker the pericarp.?4?The correlations between the skin thickness and endogenous hormone content,metabolism-related enzyme activities and gene expression levels of KT/CJ and KT/PT were analyzed.It turned out that the contents of IAA,GA₃ and ZT,the expression levels of GA20ox and KO in the peel of the KT/CJ were extremely significant positive correlated with the thickness of the pericarp,and the levels of IAAO,CKX activity and CKX expression were extremely significant negative correlation with it.The KT/PT did not show significant correlation.In summary,under the same management level,the differences in the thickness of pericarp of the KT/CJ and KT/PT are the result of the joint action of IAA,GA₃,ZT and their related metabolic enzyme activities and gene expression.In a certain range,the higher content of IAA,GA₃,and ZT,the higher the activity of related enzyme synthesis and gene expression,and the greater the degree of growth and development of pericarp,the thicker the pericarp.