Study On Grafting And Healing Mechanism Of Euscaphis Konishii

In order to explore the grafting healing mechanism of Euscaphis konishii and screen out the optimal grafting method,so as to speed up the breeding speed of excellent clones of Euscaphis konishii.In this study,the branches or buds on the 8-year-old Euscaphis konishii were used as scions,and the 2-year-old Euscaphis japonica seedlings were used as rootstocks for grafting propagation.The effects of different grafting methods on survival rate,growth and photosynthetic physiological characteristics of grafted seedlings were studied.The healing process of the graft interface of"Euscaphis konishii/Euscaphis japonica"was observed microscopically and the activities of nutrients and related enzymes were determined.The results of the study are as follows:(1)The effects of spring budding,cutting and splitting methods on the grafting survival rate of Euscaphis konishii were compared.The results showed that the survival rate of budding grafting was the highest,up to 89.2%,which was significantly higher than that of splitting grafting(50.8%)and cutting grafting(42.5%),but there was no significant difference between splitting grafting and cutting grafting.(2)The effects of budding in different stages on the grafting survival rate of Euscaphis konishii were compared.The results showed that the survival rate of grafting in spring from February to March(before bud sprouting until leaf spreading)was significantly higher than that at the end of July in summer.(3)The growth of new shoots and photosynthetic capacity of leaves of three grafted seedlings were compared.The results showed that the length and thickness of shoots were the largest in the budding seedlings,and the difference was significant compared with the split seedlings and the cut seedlings.However,there was no significant difference in the length and thickness of new shoots between split seedlings and cut seedlings.The results of correlation analysis showed that there was a significant positive correlation between the length of new shoots and the diameter of grafted seedlings(r=0.737);They were positively correlated with leaf net photosynthetic rate(P_n),stomatal conductance(G_s)and transpiration rate(T_r);There was a significant positive correlation with leaf greenness(SPAD).The results showed that the stronger the photosynthetic capacity of the grafted seedlings,the greater the growth of their new shoots.The comprehensive evaluation results of membership function showed that the photosynthetic capacity of leaves of budding seedlings was the strongest,followed by the split seedlings and the cut seedlings was the weakest.(4)The grafting and healing process of Euscaphis konishii can be divided into three stages.The first stage was 0～10 days after grafting,which was the period of isolation layer and callus formation.Among them,the rootstock incision isolation layer and callus began to form on the 3rd and 5th days after grafting,which were 3 and 5 days earlier than that of the scion,respectively.The second stage was 11～20 days after grafting,which was the period of callus division,proliferation and connection.On the14th day after grafting,callus bridge was formed and the isolation layer disappeared.On the 20th day after grafting,cambium ring was formed at the binding site of rootstock and scion,indicating that the grafting healing was completed.The third stage was 21～26days after grafting,during which callus differentiated into vascular tissue at the binding site of rootstock and scion.On the 26th day after grafting,cambium cells differentiated into new ducts and screens,indicating the survival of the graft.After that,the newly differentiated vascular bundles were further differentiated to form a mixed population of vascular bundles.(5)The physiological and biochemical changes in the healing process of the grafts of"Euscaphis konishii/Euscaphis japonica"are as follows:the period of isolation layer and callus formation,the content of soluble protein,POD,CAT and PPO activities increased,SP and PAL activity decreased.In the period of callus division,proliferation and connection at the junction of rootstock and scion,the content of soluble sugar and the activity of PAL increased,the content of soluble protein and the activity of PPO decreased,while the activities of POD and CAT first decreased and then increased.In the period of callus differentiated into vascular tissue formation,the content of soluble sugar in the binding site of the stock and scion did not change significantly,the content of soluble protein and the activities of CAT and PAL decreased,while the activities of POD and PPO increased.The principal component analysis showed that the main physiological and biochemical indexes affecting the graft healing of Euscaphis konishii were soluble sugar,soluble protein,PPO and CAT.