南方红豆杉根系分泌物促进喜树幼苗生长和喜树碱积累的化感作用机制

Allelopathy plays an important effect on artificial mixed forest cultivation successfully. Camptotheca acuminata, as a national emphasis protection wild plant, its resource crisis has risen. Nowadays, the growth of C. acuminata artificial pure forest is poor, therefore, it is urgent to select the appropriate species cultivated with C. acuminata. The preliminary study by project team showed that the mixed forest of C. acuminata and Taxus chinensis var. mairei has an advantage over the growth of C. acuminate and proved that root exudates in T. chinensis var. mairei significantly promoted the C. acuminata seedling growth and camptothecin (CPT) accumulation. Our further study as follows, after T. chinensis var. mairei root exudates are trapped by CRETS, allelopathy parts for promoting the C. acuminata growth and CPT accumulation are confirmed using different polar parts irrigating C. acuminata seedling. The chemical components in allelopathy parts are identified by LC/MS、GC/MS、IR、NMR, then the influence of identified chemical components on C. acuminata growth，CPT accumulation are examined and further find allelopathy compounds. The allelopathy compounds are micronized by supercritical fluid technology. The influence of allelopathy compounds on C. acuminata seedling growth，physiological index, CPT synthesis key precursors contents and key enzyme activities will be tested by uniform design method. In the study, our aim is to illustrate an important allelopathy mechanism of T. chinensis var. mairei root exudates on promotion C. acuminata growth and CPT accumulation and provide a scientific reference basis for deeply understanding of alelopathy effect on choosing mixture species in artificial mixed forest cultivation.

化感作用是影响人工混交林培育成功与否的重要因素之一。喜树作为国家重点保护野生植物，资源濒临危机。喜树人工纯林生长较差，亟需选择合适树种进行喜树混交林培育。项目组前期研究表明：喜树与南方红豆杉混交对喜树生长有利；南方红豆杉根系分泌物可显著促进喜树幼苗生长和喜树碱积累。本项目拟通过CRETS捕集南方红豆杉根系分泌物；以分泌物不同极性段分别浇灌喜树幼苗，确定化感部位；采用LC/MS、GC/MS、IR、NMR对化感部位中的化学成分进行鉴定；测试鉴定出的化学成分对喜树幼苗生长和喜树碱积累的影响，明确化感成分；应用超临界流体技术制备代表化感成分超微粉；采用均匀设计法设定不同浓度代表化感成分组合，并考察其对喜树幼苗相关生长和生理指标、喜树碱合成关键前体含量与关键酶活性的影响，旨在阐明南方红豆杉根系分泌物对喜树幼苗生长和喜树碱积累的促进机制，为实践上培育喜树人工林时选择合适混交树种提供化感方面理论依据。

化感作用是影响人工混交林培育成功与否的重要因素之一。喜树作为国家重点保护野生植物，资源濒临危机。喜树人工纯林生长较差，亟需选择合适树种进行喜树混交林培育。项目组前期研究表明：喜树与南方红豆杉混交对喜树生长有利；南方红豆杉根系分泌物可显著促进喜树幼苗生长和喜树碱积累。本项目通过CRETS捕集南方红豆杉根系分泌物；以分泌物不同极性段分别浇灌喜树幼苗，确定化感部位为水溶性极性段；采用LC/MS、GC/MS、IR、NMR对化感部位中的化学成分进行鉴定，确定化感成分为4种紫杉烷类化合物：紫杉醇（Paclitaxel）、三尖杉宁碱（Cephalomannine）、巴卡亭Ⅲ（Baccatine III）和10-脱乙酰基紫杉醇（10-Desacetyl Paclitaxel）；应用超临界流体技术制备4种化感成分超微粉并考察其对喜树幼苗相关生长和生理指标、喜树碱合成关键前体含量与关键酶活性的影响，结果表明4种紫杉烷类成分可以促进喜树叶片叶绿素含量提高，同时提高色胺酸脱羧酶（TDC）活性，推测这就是南方红豆杉根系分泌物对喜树幼苗生长和喜树碱积累的促进的主要机制。项目研究结果可为实践上培育喜树人工林时选择合适混交树种提供化感方面理论依据。