Research On Anatomical,physiological And Biochemical Traits Of Union Of Carya Illinoensis Bud Grafting

Pecan(Carya illinoensis) belongs to carya,juglandaceae,it is a kind of dry fruit tree and woody oil plant with very high quality.In this research,two pecan materials—bud that developed on 1a shoots of variety “Pawnee” as scion,1a seedling as stock—were choosen for patch budding.In order to provide theory basis for bud grafting on pecan,we studied the anatomical, physiological and biochemical mechanism of bud grafting union by:observing the histological changes during grafting healing; determining several physiological and biochemical values in different stages after grafting.The main conclusions were as follows:(1)There were five stages during budding union: the formation and thickeness of isolation layer,the initial connection between scion and stock(3d); by sequential dedifferentiation,the calli primarily formed from cambium cells of stock and scion(5-6d);isolation layer was broken by the proliferation of calli,and calli connected scion and stock(6-12d);the parenchymal cell near cambium of stock and scion differentiated new cambium ring which connected stock and scion(12-18d);new phloem and xylem were differentiated from cambium ring,and formed vascular tissue that intercommunicated stock and scion(21-30d);stock and scion became a whole body and survived(40d).(2)The POD activity increased to the first peak in 10 d after grafting,which favor the calli connection between stock and scion;PPO activity increased in the beginning(0-3d) and protected the wound from external invasion,meanwhile,this process may thicken the isolation layer,thus hinder graft union; at earlier stage(0-5d),IAAO activity increased to reducted excessive IAA,and then decreased for accumulation of IAA(5-40d),which favor union;the synthesis of lignin was accelerated by increasing activity of POD,PPO,PAL,the activities get a peak in 22,22,18 d after grafting, respectively,that improved vascular formation and graft survival.Each kind of enzyme made influence in specific period of healing.(3)The content of soluble sugar and soluble protein in grafts were generally higher than that in seedling,they were largely consumed as material and energy basis.At most of the time,the content of starch in grafts were higher than that in seedlings,the starch acted as energy basis,furthermore,the content remarkably increased since 10 d,that indicates it was involved in the differentiation of calli.Tannin can be easily oxidized to insoluble solid by air,which had adverse effect for healing,its content gradually decreased;IAA improved cell division and induced vascular formation,its content in grafts increased since 5d,and kept a higher level relative to seedlings.ZR improved cell division,the level of grafts increased during 7-18 d and significantly higher than seedlings.GA3 had inhibition on this process,the content in grafts generally lower than that in seedlings.From the results above,we concluded that IAA and ZR had promotion on grafts union,GA3 held the contrary;ABA had inhibition on the proliferation of graft tissue in vascular formation period(22-40d),regulated the changes from proliferation to differentiation,which favors grafts union. IAA and ZR had synergistic effect,IAA play a leading role during5-14d(the proliferation of calli),31-40d(the differentiation of vascular bundle),ZR play a leading role during 8-22d(the division of cambium layer cells).IAA and ABA had antagonistic effect,which can be seen by a higher IAA/ABA rate of grafts relative to seedlings.