Tissue anatomy and physiological characteristics of grafting healing process of Litsea cubeba
[Objective]By analyzing the organizational structure of the grafting interface and the physiological characteristics of the grafting site,the mechanism of the budding healing process of Litsea cubeba has been clarified,which has important technical guidance significance for the production of high-quality L.cubeba grafted seedlings.[Method]The L.cubeba annual seedlings was employed as rootstocks,and the annual branches of superior trees in the scion garden as ear strips.Based on the inlay budding grafting technology,the tissues at the grafting junction were sampled at different budding stages for microscopic observation and analysis of the anatomical structure.In addition,the activities of physiological enzymes,including soluble starch,soluble sugar,soluble protein,peroxidase(POD),superoxide dismutase(SOD),catalase(CAT),polyphenol oxidase(PPO),phenylalanine ammonia lyase(PAL),were measured.[Result]The grafted healing process of L.cubeba could be divided into four stages:isolation layer formation stage(0-5 days after grafting),callus formation and connection stage(6-16 days after grafting),cambium connection stage(17-25 days after grafting)and vascular tissue differentiation and formation stage(26-35 days after grafting).In the early grafting stage,isolation layer and callus tissue appeared successively on the cutting surface of the grafting interface rootstock.17-25 days after grafting,a callus bridge was formed between the rootstock and the scion,and cambium was connected to each other,forming cambium ring.Vascular tissues were differentiated from the grafting interface 26-35 days after grafting,and the rootstock and scion were tight junction.There were significant differences among various physiological indicators.On the 15th day after grafting,all soluble starch,soluble protein,POD,and CAT rose to the peak levels.On the following 5 days,soluble sugar and SOD reached the highest value,at which point PPO activity significantly decreased.[Conclusion]The healing process of L.cubeba is basically completed on the 35th day after grafting.The key period for survival of L.cubeba grafting is the late stage of callus formation,the early stage of cambium connection(15-20 days after grafting).During the formation of the isolation layer,three antioxidant enzymes(SOD,POD,CAT)immediately regulate the level of reactive oxygen species;In the late stage of grafting healing,POD,CAT,and PAL jointly participate in the formation of callus and lignification process at the cutting site of the rootstock.
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