The Extraction,Isolation and Identification of Exudates from the Roots of Flaveria bidentis

Large amounts ofFlaveria bidentis＇s root culturing solution were obtained by using DFT （deep flow technique） equipment and these solution which was vacuum concentrated （10, 20 mg mL-~） can have a certain inhibition on Triticum aestivum, Cucumis sativus, Raphanus sativus, Amaranthus retroflexus, Setaria viridis, Chenopodium album, Echinochloa crusgalli and Chloris virgata. This outcome suggested some active compounds in the root exudates ofFIaveria bidentis can inhibit the germination, seedling elongation and root length. The dichloromethane extract of root exudates was identificated by GC-MS, and 29 kinds of compounds, including esters, hydrocarbons, ketones, thiazole, amines, etc. were obtained and the phthalate n-octyl ester, phthalate 2-ethylhexyl ester were proved to be allelochemicals. The culturing solution of root exudates was separated through the resin column and silica gel column and a component inhibiting seedling height, root length and fresh weight of wheat was got. There were 6 kinds of organic compounds in this component including dioctyl phthalate, 1,2-phthalate, mono（2-ethylhexyl） ester by GC-MS.

Isolation and Structural Identification of Herbicidal Active Substance from Root of Flaveria bident(L.) Kuntze

In order to understand the composition and structure of herbicidal active substance from the root of Flaveria bidentis （L.） Kuntze, the isolation and structural identification were researched in this paper. The crude extract from the root ofF. bidentis （L.） Kuntze was extracted by petroleum ether, ethyl acetate, and water saturation of n-butyl alcohol, respectively, and the extraction fluid was separated by using the method of TLC, then the main fraction was separated by HPLC, and the structure of the herbicidal active substance was analyzed by LC-MS, elemental analysis and ~H-NMR. The results showed that the petroleum extraction had the strongest herbicidal activity, and the purple blue stripe separated by TLC had the strongest effect on Digitaria sanguinalis. The herbicidal active substance was identified as ct-terthienyl according to the data of LC-MS, elemental analysis and 1H-NMR.

气候变化情景下中国外来入侵植物黄顶菊潜在分布区模拟与早期预警

20世纪90年代外来植物黄顶菊(Flaveria bidentis)入侵中国,威胁我国的农业生产和生态安全,现已在河北省8个地级市、天津市、河南省6个地级市、山东省5个地级市、山西省长治市广泛分布,并呈迅速扩散蔓延趋势,预测黄顶菊在中国的潜在分布区可为阻断其传播和早期预警提供参考.本文基于黄顶菊在南美洲原产地的分布数据和环境变量构建本土生态位模型,投影至我国并预测当前和未来气候情景下黄顶菊的潜在分布格局.结果表明:①黄顶菊潜在分布范围涵盖华北平原、东北平原、黄土高原和云贵高原.与黄顶菊实际分布区相比,山东省中部、北京市中南部、辽宁省南部、山西省南部、陕西省中部具有较大面积的中-高潜在适生区,黄顶菊在中国尚未达到其最大潜在分布范围,仍有可能继续扩散.②全球变暖导致黄顶菊潜在适生区明显向北扩张、向南收缩,分布中心由华北中纬度地区向东北高纬度地区迁移.③综合比对黄顶菊实际分布状况及其在不同气候情景下潜在分布的变化趋势,结合国家和地方的管控需求,以地级及以上城市行政区为管控单元划定重点管控区、重点监测区和重点预防区,建议在黄顶菊扩散前缘区加强监测阻截力度,逐步消除黄顶菊发生区的生态影响,重点监测其潜在适生分布,抑制其向邻近地区进一步扩散蔓延.研究显示,黄顶菊在我国仍具有较大的潜在分布空间,全球变暖加剧其向东北高纬度地区迁移,基于黄顶菊的潜在适生区变化趋势制定分级监管策略在一定程度上可提升防控效率,以防止其进一步扩散.

芽孢杆菌通过提高黄顶菊对氮和磷的吸收促进外来黄顶菊的入侵

外来植物入侵对土壤芽孢杆菌(Bacillus)多样性的影响及芽孢杆菌在外来植物入侵中的作用目前尚不清楚。黄顶菊(Flaveria bidentis)是入侵中国的有害杂草,狗尾草(Setaria viridis)是黄顶菊入侵地常见的伴生植物种。本研究利用野外大田试验和温室盆栽试验,比较黄顶菊和狗尾草根际土壤芽孢杆菌群落结构的差异,以及黄顶菊和狗尾草根际土壤芽孢杆菌对黄顶菊竞争生长的影响。野外大田试验包括黄顶菊单种、黄顶菊和狗尾草混种、狗尾草单种3个处理。利用16S rRNA基因测序技术研究了不同处理两种植物根际土壤芽孢杆菌的多样性,获知黄顶菊根际土壤聚集的优势芽孢杆菌;利用温室盆栽试验探究优势芽孢杆菌对黄顶菊竞争生长的影响。研究结果表明,黄顶菊和狗尾草根际土壤芽孢杆菌多样性差异显著,其中耐寒芽孢杆菌是黄顶菊和狗尾草根际土壤聚集的优势芽孢杆菌,但是黄顶菊根际土壤中耐寒芽孢杆菌相对丰度显著高于狗尾草根际土壤耐寒芽孢杆菌的相对丰度。接菌试验表明,与狗尾草根际土壤中的耐寒芽孢杆菌相比,黄顶菊根际土壤聚集的耐寒芽孢杆菌提高了黄顶菊体内氮和磷的水平。总之,黄顶菊入侵改变了根际土壤芽孢杆菌的群落结构,黄顶菊根际土壤聚集的耐寒芽孢杆菌通过提高黄顶菊植株体内氮、磷水平来促进黄顶菊的生长。