山苍子嫁接愈合过程的组织解剖和生理特性

Tissue anatomy and physiological characteristics of grafting healing process of Litsea cubeba

【目的】通过分析山苍子嫁接愈合过程中嫁接口的组织结构和生理特性变化过程,明确山苍子芽接愈合过程的机制,对山苍子良种嫁接苗木的生产具有重要的指导意义。【方法】以山苍子1年生实生苗为砧木,以采穗圃优树1年生枝为穗条,采用嵌芽接嫁接技术,于芽接后不同时期取嫁接结合部位组织进行解剖结构的显微镜观察和分析,并测定可溶性淀粉、可溶性糖、可溶性蛋白、过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)等生理酶指标活性。【结果】山苍子嫁接愈合过程可分为4个时期:隔离层形成期(嫁接后0~5 d)、愈伤组织形成与连接期(嫁接后6~16 d)、形成层连接期(嫁接后17~25 d)和维管组织分化形成期(嫁接后26~35 d)。在嫁接后初期,嫁接口的砧木切口面先后出现隔离层和愈伤组织,嫁接后17~25 d,砧穗间形成愈伤组织桥,且形成层相互连接,构成形成层环带;嫁接后26~35 d嫁接口处分化出维管组织,且砧穗紧密连接。各生理指标变化存在显著差异,在嫁接后第15天,可溶性淀粉、可溶性蛋白、POD、CAT均上升到峰值水平,随后5 d,可溶性糖和SOD出现峰值,此时PPO活性显著降低。【结论】山苍子在嫁接后第35天基本完成愈合,且愈伤组织形成与连接末期、形成层连接初期(嫁接后第15~20天)是山苍子嫁接成活的关键时期。在隔离层形成期,3种抗氧化酶(SOD、POD、CAT)即时调控活性氧水平;在嫁接愈合后期(嫁接后30~35 d),POD、CAT与PAL共同参与砧穗切口部位愈伤组织形成与木质化过程。

【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.