13C-NMR spectroscopy studies of humic substances in subtropical perhumid montane forest soil

We investigated soil organic matter in a forest of natural Hinoki cypress (Chamaecyparis obtusa) under perhumid weather conditions in north central Taiwan. Humic substances along the transect from the summit and footslope to lakeshore were characterized by use of solid-state cross-polarization, magic-angle-spinning ¹³C nuclear magnetic resonance spectroscopy (CP/MAS ¹³C-NMR). The major components of soil organic carbon in whole soil and humic substances were alkyl-C, O-alkyl-C, and di-O-alkyl-C, ranging from 60.6% to 80.7%, then aromatic-C, 7.5% to 9.8%. The degree of humification of soil organic matter, both O-alkyl-C/alkyl-C ratio and aromaticity, decreased slightly from the summit to lakeshore. The content of functional groups of polar and acidic groups, including O-alkyl-C, di-O-alkyl-C, and carboxyl-C, corresponded with the topographical effect, increasing slightly from the summit to lakeshore. However, the relatively low degree of humification in soils of this perhumid forest and low aromaticity were due to high precipitation and acidity, which appeared to hinder organic matter decomposition with topography change.     

我国水稻上一种类似条纹叶枯病的探讨

 为了弄清我国类似水稻条纹叶枯病的病原及其生物学特性,自1984年起,选用我国的病株进行了有关测试.人工接种,该病原物能侵染水稻、早稻和小麦,不能侵染玉米、高粱和苏丹草.在大量的病组织超薄切片和分离提纯液的电镜观察中,均未见到分枝丝状体病毒,病株汁液和提纯液与日本的RSV抗血清均为阴性反应.此外,本实验还从类菌原体、类病毒和虫毒等方面进行了测试,除虫毒拟有一定的可能性外,其余都可以排除在真正病原之外。     

京津大白菜及其他十字花科作物霜霉病菌生理分化的初步研究

 应用十字花科蔬菜三属七种32个品种作为鉴定寄主,对京津地区12种十字花科蔬菜(大白菜、油青菜、芜菁、芥菜、大头青、雪里蕻、甘兰、苤兰、花椰菜、芥兰、萝卜和荠菜)上采集的34个霜霉病菌(Pronospora parasitica(Pers.) Fr.)标样进行了生理分化的研究。     

苦楝中几种杀虫有效成分对菜青虫和亚洲玉米螟的生物活性

采用生物活性追踪法,从苦楝根皮、树皮和果实中分离出多种四环三萜类杀虫有效成分。这些成分对菜青虫和亚洲玉米螟均表现出明显的拒食活性,川楝素对菜肯虫还有明显的胃毒活性。从苦楝中分离出的几种非四环三萜类物质对昆虫的生物活性均较低,仅表现出一定的拒食活性。另外对几种三萜衍生物的生物活性进行了测定与比较。     

甜菜花叶病毒病研究之二——感病细胞超微结构观察

对不同时期感染甜菜花叶病毒(BtMV)的叶片,进行病理变化系列观察。早期侵染(7天前)的细胞质、细胞器均无变化,随着症状发展,风轮状内含体、束状内含体、细胞核卫星体,细胞质泡囊化旁类似病毒的束状结构,20天达到了高峰,风轮状及束状内含体一直持续两个月还存在。田间样品也观察到了典型的风轮状及束状内含体。细胞核卫星体出现很少。侵染后期,细胞质减少,叶绿体比相应健株提前出现淀粉粒,噬锇颗粒等,基粒片层也提前消解,表现细胞提前衰老的特征。此外细胞内还有许多健株没有的泡状结构。一种为旁壁体,可能与细胞壁加厚有关;一种为多重泡体的叠加,可能是液泡的吞噬作用加强与外源物质(BtMV)侵入有关;另外还有一种可能是过氧化物酶体或线粒体在病毒诱导下泡囊化,其作用不清楚。     

引起哈密瓜坏死的两种病毒的分离及鉴定

 从哈密瓜上分离到两种引起坏死症状的病毒,称为哈密瓜坏死病毒(HmNV)和哈密瓜叶脉坏死病毒(H-mVNV).两者都能系统感染哈密瓜,响影植株滞长.