Abstract:In order to explore the variation law of rejuvenation based on tissue culture,we selected 10-year-old Pyrus betulifolia for continuous subculture,and then counted the propagation coefficient and rooting rate of multiple shoots of different subculture passages,observed and recorded the morphological changes of leaves and measured the content of endogenous hormones.The results showed that: (1)The rooting rate of multiple shoots increased from 0 to 66.70% and the propagation coefficient increased from 2.13 in the first subculture to 4.20 through continuous subculture.(2)The leaves showed a lobes at 3th subculture and then the degree of lobes gradually deepened;During the continuous subculture, leaf area and vein number of multiple shoots were decreased significantly,leaf perimeter and leaf index showed a trend of decreasing first and then increasing.(3)The endogenous IAA content of multiple shoots reached 46.39ng·g-1 at 6th subculture, which was significantly higher than that of 0th subculture;With the increase of subculture passages,the endogenous ZR showed a trend of increasing first and then decreasing, and the endogenous GA3 content did not change significantly, while the endogenous ABA content gradually decreased,in the leaves;The values of IAA/ABA and IAA/ZR in the leaves increased with the number of subculture.(4)The ABA content and IAA/ZR of multiple shoots leaves showed significant negative correlation and significant positive correlation with rooting rate,The number of leaf lobes and IAA/ABA shwed a significant positive correlation with rooting rate,while the number of leaf veins showed a significant negative correlation with rooting rate.It can be seen that continuous subculture significantly can improve the rooting ability of Pyrus betulifolia multiple shoots, and it is closely related to leaf morphology and hormone content and ratio of multiple shoots ,which provides reference for vegetative propagation of difficult rooting plants.