胜红蓟化感作用研究Ⅰ.水溶物的化感作用及其化感物质分离鉴定

研究了胜红蓟水溶物对植物的化感作用 .结果表明 ,胜红蓟水溶物溶液浓度在0 .2 5gFW·ml- 1 时对所有供试植物的萌发和幼苗生长均有显著的抑制作用 ,浓度降至0 .1 0 gFW·ml- 1 时其抑制作用基本消失 ;胜红蓟不同器官、不同生育期水溶物的化感作用是有差异的 ,特别是不同生境条件下生长的胜红蓟水溶物化感作用有显著差异 ,表明在恶劣生境下胜红蓟的化感作用更为强烈 .对胜红蓟水溶物中的化感活性物质进行分离和分子结构鉴定 ,得到早熟素Ⅰ、早熟素Ⅱ和 5,2 2 二烯 3β 豆甾醇 3个化感化合物 .     

胜红蓟化感作用研究 Ⅱ.主要化感物质的释放途径和活性

研究了南方重要杂草胜红蓟(Ageratumconyzoides)挥发物质的化感作用。结果表明,胜红蓟鲜叶的挥发物质和挥发油对所有受试植物的幼苗生长有显着的抑制作用。用色谱法鉴定并分离了胜红蓟挥发油的主要成分早熟素Ⅰ和早熟素Ⅱ,两者分别占总量的30.93%和51.61%.胜红蓟水溶物中的早熟素Ⅰ和Ⅱ是从挥发物中而来,挥发是胜红蓟释放化感物质的主要途径。分离纯化的早熟素Ⅰ和Ⅱ的饱和水溶液对萝卜、番茄和黑麦草的幼苗生长均有显着的抑制作用,特别是早熟素Ⅱ具有强烈的化感作用,在25μg·ml^-1低浓度下,仍能抑制植物幼苗的生长,但早熟素Ⅰ和Ⅱ的混合溶液对植物的抑制作用并无显着增强,两者之间不存在协同作用。     

胜红蓟化感作用研究Ⅱ.主要化感物质的释放途径和活性

研究了南方重要杂草胜红蓟（Ａｇｅｒａｔｕｍｃｏｎｙｚｏｉｄｅｓ）挥发物质的化感作用．结果表明,胜红蓟鲜叶的挥发物质和挥发油对所有受试植物的幼苗生长有显著的抑制作用．用色谱法鉴定并分离了胜红蓟挥发油的主要成分早熟素Ⅰ和早熟素Ⅱ,两者分别占总量的３０．９３％和５１．６１％．胜红蓟水溶物中的早熟素Ⅰ和Ⅱ是从挥发物中而来,挥发是胜红蓟释放化感物质的主要途径．分离纯化的早熟素Ⅰ和Ⅱ的饱和水溶液对萝卜、番茄和黑麦草的幼苗生长均有显著的抑制作用,特别是早熟素Ⅱ具有强烈的化感作用,在２５μｇ·ｍｌ－１低浓度下,仍能抑制植物幼苗的生长,但早熟素Ⅰ和Ⅱ的混合溶液对植物的抑制作用并无显著增强,两者之间不存在协同作用．     

胜红蓟化感作用研究I.水溶物的化感作用及其化感物质分离鉴定

研究了胜红蓟水溶物对植物的化感作用,结果表明,胜红蓟水溶物溶液浓度在０．２５ｇＦＷ．ｍｌ＾－１时对所有供试植物的萌发和幼苗生长均有显著的抑制作用,浓度降至０．１０ｇＦＷ．ｍｌ＾－１时其抑制作用基本消失,胜红蓟不同器官,不同生育期水溶物的化感作用是有差异的,特别是不同生境条件下生长的胜红蓟水物化感作用有显著差异,表明在恶劣生境下胜红蓟的化感作用更为强烈,对胜红蓟水溶物中的化感活性物质进行了分离和分子     

胜红蓟化感作用研究Ⅲ.挥发油对不同营养水平下植物的化感作用

研究了胜红蓟挥发油对不同营养水平下植物的化感作用．结果表明,随着营养水平的降低,胜红蓟挥发油对受试植物的化感作用明显增强．在胜红蓟挥发油的作用下,受试植物叶绿素和可溶性蛋白含量明显降低,过氧化物酶（ＰＯＤ） 活性降低,而质膜相对透性增加,丙二醛（ ＭＤＡ） 含量升高．利用ＧＣ／ ＭＳ对胜红蓟挥发油的组成和含量进行了分析,共鉴定１６ 种物质,其中早熟素Ⅱ、早熟素Ⅰ和子丁香烯为主要成分,相对含量分别为３６ ．８５ ％ 、２６ ．４１ ％ 和１９ ．８４ ％ ．     

胜红蓟地上部化感作用物的分离与鉴定

 胜红蓟(Ageratum conyzoides)是华南地区的重要杂草,具有显著的化感作用。本文利用色谱和波谱技术对胜红蓟地上部化感活性成分进行分离和化学结构鉴定,得到两个化感作用物质：胜红蓟素(6,7—二甲氧基—2,2—二甲基色烯)和5,22—二烯—3β—豆甾醇。对这两个作用物的化感作用研究表明：胜红蓟素对受体幼苗生长有抑制作用,500×10-6处理对稗草生长达到完全抑制,对萝卜的抑制率也高达90％。浓度降到25×10-6对稗草和萝卜幼苗生长仍具有显著的抑制作用。     

胜红蓟化感作用研究 Ⅷ.植株对花生和相关杂草的田间化感效应

在田间条件下,胜红蓟化感效应与处理植株的方式和时间显相关。覆盖处理对花生出苗和生长不产生化感抑制效应,而是显示一定的促进效应,翻埋处理对花生出苗和生长都产生显的化感抑制效应,然而覆盖处理30d,翻埋处理10d后再播种花生,花生出苗均受显抑制,两种处理都能减少许多杂草的萌发,但对不同种属杂草萌发的抑制作用有差异。进一步用高效液相色谱（HPLC）技术研究证实;覆盖处理条件下,胜红蓟植株直到第14天才向土壤中缓慢释放化感物质胜红蓟素,第30天达到最大值后逐渐减少,而翻埋处理的第2天,植株就向土壤中释放胜红蓟素,第10天达到最大值后缓慢减少,但第26天后土壤中胜红蓟素含量又上升,然后再逐步下降。这些结果显示不同处理条件下,胜红蓟植株对花生和相关杂草的田间化感效应是与胜红蓟植株在不同时间释放的化感物质在土壤中的存在状态和有效作用浓度显相关的。     

胜红蓟化感作用研究 Ⅸ.主要化感物质在土壤中的转化

在田间条件下,胜红蓟挥发油能抑制花生的出苗和生长发育,进一步用高效液相色谱（HPLC）研究证实;胜红蓟挥发油中的主要化感物质胜红蓟素在土壤中的转化与土壤的有机质和营养元素水平显著相关,在高有机质和营养元素水平的土壤中,胜红蓟素先聚合形成二聚体,26d后又解聚成胜红蓟素,然后逐步降解成苯甲酸类,2-甲基丙酸和乙酸等小分子,而在低有机质和营养元素水平的土壤中,胜红蓟素不经过二聚化过程,而是直接降解成小分子,经液质（LC/MS）和核磁共振（NMR）等技术分离鉴定了胜红蓟素二聚体的结构,生物测定表明：胜红蓟素二聚体对花生和黑牧草的生长没有抑制活性。     

胜红蓟化感物质之间相互作用的研究

 通过柱层析从胜红蓟挥发油中分离出早熟素Ⅰ、早熟素Ⅱ、子丁香烯、3,3-二甲基-5-特丁基茚酮、红没药烯、乙酸葑醇酯等6种主要化感物质(占挥发油总量的97％),并研究了这些化感物质在挥发、淋溶(饱和水溶液)和土壤降解途径下对萝卜,番茄和绿豆幼苗的化感作用。结果表明：早熟素Ⅰ、早熟素Ⅱ、3,3-二甲基-5-特丁基茚酮及子丁香烯(挥发途径)虽有较强的化感活性,但均弱于挥发油的化感活性,而子丁香烯(淋溶途径),红没药烯和乙酸葑醇酯则基本无化感活性。但是,早熟素n和无活性的三个化感物质结合,则表现出强烈的化感活性,说明胜红蓟各化感物质之间存在着明显的协同作用。     

胜红蓟黄酮类物质对柑桔园主要病原菌的抑制作用

柑桔园引种杂草胜红蓟能有效地控制主要病害,研究发现,胜红蓟产生并释放到土壤中的黄桐类物质对疮痂病菌、炭疽病菌、白粉病菌和烟煤病菌等柑桔园主要病原真菌具有抑制活性,从胜红蓟植株中分离鉴定了10个黄酮物质,包括一个糖甙黄酮分子,但胜红蓟植株产生的大部分黄酮物质在土壤中会逐渐降解,只有3个黄酮分子能在柑梧园的土壤中累积并存在较长时间,而这3个黄酮物质对柑桔园主要病原真菌具有显著的抑制活性,其活性不仅超过胜红蓟释放的其化感物质,而且强于商业的杀菌剂多菌灵,表明胜红蓟产生和释放的黄酮物质在柑桔园病害控制中起着重要作用。     

Roles of Allelopathy in Plant Biodiversity and Sustainable Agriculture

Allelopathic compounds are metabolites released from plants that might be beneficial or detrimental to the growth of receptor plants. These compounds are involved in the environmental complex of managed or natural ecosystems. Allelopathic compounds have been shown to play important roles in the determination of plant diversity, dominance, succession, and climax of natural vegetation and in the plant productivity of agroecosystems. The overuse of synthetic agrochemicals often causes environmental hazards, an imbalance of soil microorganisms, nutrient deficiency, and change of soil physicochemical properties, resulting in a decrease of crop productivity. The incorporation of allelopathic substances into agricultural management may reduce the use of synthetic herbicides, fungicides, and insecticides and lessen environmental deterioration. Scientists in many different habitats around the world have demonstrated the above examples previously. It is known that most volatile compounds, such as terpenoids, are released from plants in drought areas. In contrast, water-borne phytotoxins, such as phenolics, flavonoids, or alkaloids, are released from plants in humid zone areas. Both allelopathy and autointoxication play an important mechanism in regulating plant biodiversity and plant productivity. A unique case study of a pasture-forest intercropping system, which is particularly emphasized here, could be used as a model for forest management. After the deforestation of coniferous or hardwood forests, a pasture grass, kikuyu grass (Pennisetum clandestinum), was transplanted onto the land. The grass was quickly established within 6 months. Significant suppression of weed growth by the kikuyu grass was found; however, the growth of coniferous or hardwood plants was not suppressed but stimulated. This example as well as others described in this text clearly indicate that allelopathy plays a significant role in sustainable agriculture. Nevertheless, room for allelopathic research in the next century is available for biologists, biochemists, biotechnologists, and chemists. Future allelopathic research should focus on the following tasks: (1) a continuous survey of potential allelochemicals from natural vegetation or microorganisms, (2) the establishment of practical ways of using allelochemicals in the field, (3) to understand the mode of action of allelopathic chemicals in receptor organisms, (4) to understand the role of allelopathic chemicals in biodiversity and ecosystem function, (5) to explore advanced biotechnology for allocating allelopathic chemical genes in plants or microorganisms for biological control, and (6) to challenge the natural product chemists to develop a better methodology for isolating allelopathic compounds or their degraded compounds from the environment, particularly the soil environment.     

菊科植物化感作用研究进展

对菊科植物化感作用的研究进展进行了综述。菊科植物中至少有 39个属存在化感作用 ,特别是一枝黄花属、向日葵属、胜红蓟属、银胶菊属、蒿属植物等有较多的研究报道。鉴定出的化感物质多为萜类、聚乙炔类、酚类、有机酸类等 ,这些化感物质对多种受体植物表现出程度不同的抑制或促进的效应。其化感作用机理表现在破坏受体膜系统的稳定性及水分平衡关系、抑制氧化磷酸化、促进或阻滞叶绿素的合成、影响矿质元素的吸收利用等。并对菊科植物化感物质在植物生长调节剂、天然除草剂和生物杀虫剂 ,或人工合成除草剂和杀虫剂上应用的前景进行了探讨。本文显示菊科植物的化感作用将在控制外来恶性杂草及维护生态平衡上扮演重要的角色。在当前菊科植物化感作用研究的基础上 ,提出了进一步研究的 6个方向 :(1)化感物质的生物合成途径与关键酶的特性研究 ;(2 )具化感潜势物种资源的调查评价及利用研究 ;(3)化感作用在自然生态系统中的演变规律 ;(4 )菊科重要作物自毒的生化机制及克服途径 ;(5 )具应用前景的菊科植物化感关键酶的基因克隆和转基因 ,并对受体植物基因的表达与调控进行研究 ;(6 )化感作用在可持续发展农业应用上的研究与开发 ,特别是作为天然除草剂及杀虫剂     

Screening methods for the evaluation of crop allelopathic potential

There is increasing interest in the development of allelopathic crop varieties for weed suppression. Allelopathic varieties are likely to be able to suppress weeds by natural exudation of bioactive allelochemicals, thereby reducing dependence upon synthetic herbicides. Screening bioassays are essential tools in identifying crop accessions with allelopathic potential. A number of crops have been screened for this allelopathic trait, and key issues in selecting and designing screening bioassays are reviewed. It is recommended that a combination of different bioassays be used in the evaluation of crop allelopathic potential. Laboratory bioassays, field testing, and chemical screening are important steps, and none of them can be precluded if conclusive evidence of crop allelopathy is to be established. More concerted efforts are needed in screening crop germplasm before the development of allelopathic varieties occurs.     

Allelopathic Bacteria and Their Impact on Higher Plants

The impact of allelopathic, nonpathogenic bacteria on plant growth in natural and agricultural ecosystems is discussed. In some natural ecosystems, evidence supports the view that in the vicinity of some allelopathically active perennials (e.g., Adenostoma fasciculatum, California), in addition to allelochemicals leached from the shrub's canopy, accumulation of phytotoxic bacteria or other allelopathic microorganisms amplify retardation of annuals. In agricultural ecosystems allelopathic bacteria may evolve in areas where a single crop is grown successively, and the resulting yield decline cannot be restored by application of minerals. Transfer of soils from areas where crop suppression had been recorded into an unaffected area induced crop retardation without readily apparent symptoms of plant disease. Susceptibility of higher plants to deleterious rhizobacteria is often manifested in sandy or so-called skeletal soils. Evaluation of phytotoxic activity under controlled conditions, as well as ways to apply allelopathic bacteria in the field, is approached. The allelopathic effect may occur directly through the release of allelochemicals by a bacterium that affects susceptible plant(s) or indirectly through the suppression of an essential symbiont. The process is affected by nutritional and other environmental conditions, some may control bacterial density and the rate of production of allelochemicals. Allelopathic nonpathogenic bacteria include a wide range of genera and secrete a diverse group of plant growth-mediating allelochemicals. Although a limited number of plant growth-promoting bacterial allelochemicals have been identified, a considerable number of highly diversified growth-inhibiting allelochemicals have been isolated and characterized. Some species may produce more than one allelochemical; for example, three different phyotoxins, geldanamycin, nigericin, and hydanthocidin, were isolated from Streptomyces hygroscopicus. Efforts to introduce naturally produced allelochemicals as plant growth-regulating agents in agriculture have yielded two commercial herbicides, phosphinothricin, a product of Streptomyces viridochromogenes, and bialaphos from S. hygroscopicus. Many species of allelopathic bacteria that affect growth of higher plants are not plant specific, but some do exhibit specificity; for example, dicotyledonous plants were more susceptible to Pseudomonas putida than were monocotyledons. Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce. Therefore, when test plants are employed to evaluate bacterial allelopathy, final evaluation must include those species that are assumed to be suppressed in nature. The release of allelochemicals from plant residues in plots of ‘continuous crop cultivation’ or from allelopathic living plants may induce the development of specific allelopathic bacteria. Both the rate by which a bacterium gains from its allelopathic activity through utilizing plant excretions, and the reasons for the developing of allelopathic bacteria in such habitats, are important goals for further research.     

马缨丹叶片水提物与挥发油的生物活性及化学成分研究

研究了马缨丹 ( Lantana camara L.)叶片水提物和挥发油水溶液的化感作用。结果表明 ,马缨丹叶片水溶物浓度在 0 .2 5 g FW m L- 1时 ,对所有受试植物的幼苗生长均有一定的抑制作用 ,浓度降至 0 .1 0 g FWm L- 1时 ,其抑制作用显著降低 ;马缨丹叶片挥发油水溶液在浓度为 1 0 0、2 0 0、30 0 μg m L- 1时 ,对受试植物均有很强的抑制作用 ,且具有明显的浓度效应。采用 GC/MS分析了马缨丹叶片挥发油的化学成分 ,鉴定了 1 9种化感物质 ,其中α-子丁香烯和β-子丁香烯为主要物质 ,分别占挥发油含量的 1 6 .2 9%、2 2 .2 9%。     

茉莉酮酸甲酯对水稻化感物质的诱导效应

在室内和田间条件下 ,外源茉莉酮酸甲酯均能显著地诱导水稻化感物质的合成 ,而且这种诱导效应与施用茉莉酮酸甲酯的浓度和诱导时间显著相关。 0 .4 m mol/L浓度和处理后 4 8h,茉莉酮酸甲酯对水稻化感物质的诱导效应最强。同样 ,不同的水稻品种对茉莉酮酸甲酯的诱导响应也有显著差异。水稻化感品种 PI312 777和丰华占在茉莉酮酸甲酯的诱导下能很快合成大量的化感物质 ,而水稻非化感品种华粳籼的化感物质的含量虽也有所增加 ,但达不到能显示化感作用的浓度。进一步实验证明 :茉莉酮酸甲酯在处理 4 8h后虽能诱导水稻品种合成大量的化感物质 ,但这一诱导效应并不能长期维持。研究揭示 :水稻化感物质的合成可在外部因子的作用下动态变化 ,这对揭示和充分利用水稻的化感作用机制有重要意义。