小麦化感作用研究进展

小麦是世界第一大粮食作物,在农业生产中占有重要地位.然而,由于人们为保证小麦产量往往施用大量的除草剂和杀菌剂,对环境造成了极大的危害.小麦化感作用是利用小麦活体或残体向环境中释放次生代谢物质对自身或其他生物产生作用,它克服了除草剂和杀菌剂等引起的环境污染问题,具有抑制杂草控制病害的潜力.本文对已有的小麦化感作用的研究进展情况进行了综合评述.其中小麦对杂草、虫害及病害产生防御功能的主要化感物质为异羟肟酸和酚酸类物质.小麦化感物质活性的发挥除了取决于化感物质的种类外,还由小麦自身的遗传因素、环境因素和生物因素的共同作用所决定.小麦化感物质在根际土壤中的滞留、迁移和转化过程、小麦化感作用与土壤生物的关系以及相关的作用机理是小麦化感作用研究的薄弱环节,其研究方法还需进一步探索改进.小麦化感作用在植物保护、环境保护以及作物育种等方面具有广泛的应用前景,促进了小麦抗逆性的增强以及产量和品质的提高.     

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。     

化感作用及其在农业生产中的应用

简述了化感作用的概念、特点、作用机理和化感物质及释放途径。讨论了植物与植物之间,植物与微生物之间,植物与昆虫等食草动物之间的化感作用及化感理论在生产实践中的应用。应用化感理论指导建立合理的栽培、耕作制度;进行田间杂草生物控制和防治;开发新一代无公害农药;指导森林更新和建植;培育抗化感品种等。     

水稻化感作用及其分子生态学研究进展

综述了近年来国际上研究水稻化感作用的新进展,比较分析了当前常用于室内评价水稻化感作用潜力的几种生物测试法的优缺点,指出了琼脂迟播共培法是较为理想的室内生物测试法并已广泛应用于化感作用研究中。在此基础上,分析了水稻化感作用的数量遗传特性及其QTL定位的研究现状;阐明了水稻化感作用的遗传多样性及其分子生态特性;并就当前普遍关注的焦点问题：逆境条件（如低氮或高伴生杂草密度胁迫）常引起水稻化感作用潜力增大的生理过程与分子机制作了阐述。结合近年来应用差异蛋白组学和生物信息学的研究实例,阐明了逆境引起水稻化感作用增强与其酚类合成代谢相关酶蛋白表达丰度增加,萜类合成代谢相关酶蛋白表达丰度下降有关。就究竟什么是水稻的化感物质及其作用方式等问题作了分析与讨论．指出水稻的化感抑草效应是其众多化感物质综合作用的结果,应重视区分化感物质对靶标杂草的原生作用和进入土壤生态系统中经生物转化后的次生作用。根据当前植物化感作用研究的发展趋势,阐明了进一步研究水稻化感作用的焦点问题,提出了水稻化感作用的根际生物学特性与分子生态学机制,是未来国际上竞相角逐的重点研究领域,并认为以现代系统生物学理论为指导,运用基因组学、蛋白质组学和代谢组学等技术方法,是揭示这一分子生态学过程与机制的重要技术选择和优先研究领域。     

浮游藻类的化感作用研究进展

化感作用由于在水产上有着巨大的潜力,成为近年来各国的研究热点。本文综述了藻类化感作用的定义、研究方法、化感物质的作用机制、影响因素、化感作用的应用等,并对今后研究方向以及应用前景进行了展望。     

植物化感物质对种子萌发的影响

所有的化感物质都对一些植物的种子萌发产生影响.本文介绍了植物化感作用和化感物质的定义,化感物质的释放方式和种类,然后重点综述了化感物质影响种子萌发的作用机理、内外因素和生态学意义.化感物质通过影响细胞膜透性、细胞分裂生长和分化、呼吸作用、蛋白质合成、基因表达、激素合成和平衡,最终影响种子萌发.化感物质对种子萌发的影响与化感物质的种类、浓度、受体植物种类和环境条件等有关.     

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。     

辣椒根系分泌的潜力化感物质对生菜幼苗抗氧化代谢的影响

以盆栽辣椒为试验材料,采用树脂吸附萃取和气质联用仪测定辣椒根系分泌物,分析、确定其中的疑似化感物质。分别使用6种（0、2、4、8、12、16μg·mL-1）不同浓度的外源潜力化感物质处理生菜种子,通过种子发芽、幼苗生长分析其潜力化感作用,并研究其对生菜幼苗抗氧化代谢的影响。结果表明,2,6-二叔丁基苯酚（2,6-DTBP）、邻苯二甲酸二异丁酯（DIBP）和邻苯二甲酸二丁酯（DBP）为辣椒根系分泌的潜力化感物质,随三种潜力化感物质浓度的增加,生菜幼苗的谷胱甘肽（GSH）含量降低,超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）、多酚氧化酶（PPO）和抗坏血酸氧化酶（APx）活性先增加后降低。2,6．DTBP、DIBP和DBP4化感抑制作用的低限浓度分别为4、8、8pg·mL-1,三者通过降低GSH含量而损伤生菜幼苗的抗氧化代谢系统。     

环境胁迫下植物的化感作用及其诱导机制

植物化感作用是生态学研究中一个十分活跃的领域,对植物为什么和在什么条件下释放化感物质这一重要问题有不同的认识。在对环境胁迫下植物化感作用的变化及环境胁迫因子对化感物质听诱导机制等方面进行了评述后,指出植物化感化质的产生和释放是植物在环境胁迫的选择压力下形成的,植物化感作用是植物在进化过程中产生的一种对环境的适应性机制。     

化感作用水稻对无芒稗及相关田间杂草的抑制作用评价

对从500份水稻种质资源中用差时播种共培法的改进方法初步筛选出10份水稻化感抑稗材料进行了田间化感抑草评价研究.结果表明,在直播条件下,化感材料谷梅2号、吓一跳、鸡早籼、赣早籼和商糯1号等对无芒稗的抑制作用显著优于水稻无化感作用材料秀水63和春江11.化感材料Milyang54对田间总量杂草的抑制作用最强.在移栽条件下,化感材料谷梅2号、青困2号、吓一跳和鸡早籼对无芒稗的抑制作用与无化感作用材料秀水63和春江11差异及显著性水平.水稻材料间部分农艺性状差异及显著性水平,化感材料吓一跳和鸡早籼的株高较高,分蘖力较强,但顶三叶叶面积较小.     

胜红蓟化感作用研究Ⅵ.气象条件对胜红蓟化感作用的影响

在田间条件下 ,胜红蓟化感作用与光、温、水等气象要素显著相关 ,有利的光、温、水生长条件使得其化感作用减弱 ,反之增强 .春夏季温度和降水有利胜红蓟的生长 ,其化感作用减弱 ,而秋冬季温度和降水不利胜红蓟生长 ,其化感作用增强 .实验表明 ,30 0 μg·ml-1高浓度胜红蓟挥发油使受试植物不能生长 ,而6 0 μg·ml-1低浓度影响较小 ,在高温、低温和遮光等不利植物生长的条件下 ,低浓度的胜红蓟化感物质对受试植物的抑制效应显著增强 ,显示在不利的生长条件下 ,受试植物对胜红蓟化感物质的抵御能力减弱 .研究表明 ,在不利于胜红蓟及受试植物生长的气象条件下 ,胜红蓟化感作用增强 ,受试植物抵御化感物质的能力降低 ,使得胜红蓟群落中其它植物难以正常生长 ,相应地提高了胜红蓟在自然群落中的竞争优势 .化感作用和光、温、水、气象条件的共同作用是胜红蓟在自然群落中成为优势种群的重要原因之一 .     

基于化感物质释放特性的沉水植物抑藻作用模式研究进展

沉水植物对藻类的化感抑制作用,是沉水植物获取竞争优势和维持清水稳态的重要机制之一。化感物质是由植物产生并释放到水环境中的次生代谢产物,化感物质的有效释放和作用是实现沉水植物化感抑藻作用的关键环节。因此,在化感物质释放水平阐明沉水植物化感抑藻的作用模式、过程和机制具有重要意义。通过比较沉水植物化感物质释放到水环境中的种类、含量和常规急性毒性测试中化感物质的抑藻效果,发现沉水植物化感物质在释放水平上的作用模式不同于常规急性毒性试验中的单次作用。为了回答沉水植物化感物质在释放水平如何高效抑藻的问题,结合化感物质的释放特性,重点从化感物质的联合作用和持续作用等角度探讨沉水植物化感抑藻的作用模式,提出沉水植物可能通过多种化感物质低剂量持续释放的方式,实现对目标藻类的持续协同控制。今后有必要进一步结合沉水植物与目标藻类的共存系统与原位实验,借助分析化学、植物化学、细胞和分子生物学的技术手段,从生态学水平加强沉水植物化感抑藻作用机制研究。     

南瓜组培根根系分泌物的化感效应研究

使用组织培养技术、生物测试法及室内分析相结合的方法研究了南瓜组培根在不同生长时期与不同营养谐迫下(利用正交设计调节标准B₅培养基中的大量元素、微量元素、有机质和激素)根分泌物对南瓜、萝卜和小麦3种受体的种子萌发及幼苗生长的化感作用.结果表明,南瓜具有自毒作用,南瓜组培根根系分泌物对受体幼苗生长的抑制作用呈现出高抑低促的作用表型;南瓜组培根根系分泌物产生化感作用的活性与南瓜组培根生长速度有关,南瓜组培根根系分泌物的生长抑制活性以15～17d即生长速度指数末期为最高,21d生物量最大时的南瓜组培根根系分泌物的生长抑制活性最低;营养元素的改变明显影响了南瓜根系分泌物的产生,并通过筛选出能诱导南瓜组培根对受体具有强烈抑制作用的大量元素、微量元素、维生素和激素种类和含量的最优化组合,为研究南瓜化感作用营养胁迫机理提供依据.     

Conditional allelopathic potential of temperate lianas

Allelopathy is often treated as an innate characteristic of a species rather than a phenotypically plastic trait that can vary with environmental conditions. Lianas are a highly competitive, phenotypically plastic life form that typically occur in both shaded and unshaded environments. As such, we hypothesized that temperate lianas may conditionally change allocation to allelopathic chemicals in response to light availability though the expected direction of change is unclear. Shading may reduce resource availability and therefore reduce allocation to allelochemicals, induce allelopathy as a competitive mechanism, or may not be related to allelopathy. To test the conditionality of allelopathy, sun and shade leaves of five common liana species (Toxicodendron radicans, Parthenocissus quinquefolia, Celastrus orbiculatus, Lonicera japonica, and Vitis vulpina) were collected from a young deciduous forest in New Jersey, USA, and tested with laboratory bioassays to detect allelopathic potential. All liana species showed allelopathic potential, and three species exhibited induction of increased allelopathic potential in shaded environments. The two species that were not shade induced are late successional lianas that persist for long periods in forest canopies. In contrast, the inducible lianas were early successional species that typically decline with canopy closure. This research indicates that lianas have the potential to be allelopathic and allelopathic potential conditionally responds to shading only for species that would normally be excluded from the forest canopy. As early successional lianas are present throughout forest regeneration in a range of light environments, allelopathic plasticity may increase their success by differentially allocating resources based on environmental conditions.     

Harmful algal blooms of allelopathic microalgal species: The role of eutrophication

The ability of certain harmful algal species to produce and release chemicals that inhibit the growth of co-occurring phytoplankton species, here considered as allelopathy, is closely associated with competition for limiting nutrient resources. Many phytoplankton cells are known to release elevated amounts of organic compounds under nutrient limitation. Eutrophication alters the nitrogen-to-phosphorus balance and, when nutrient availability is unbalanced, nutrient limitation may result. Algal species that can compete successfully for available growth-limiting nutrient(s) have the potential to become dominant and form blooms. The stress conditions imposed by the shifted nutrient supply ratios can, in some algae, stimulate production of allelochemicals that inhibit potential competitors. Thus, under cultural eutrophication, altered nutrient (N, P) ratios and limiting nutrient supplies can stimulate increased production of allelochemicals, including toxins, by some algal species and accentuate the adverse effects of these substances on other algae. Future investigation on the characterization of the chemical compounds involved in the allelopathic process are needed to advance the study of the mode of action of phytoplankton allelochemicals.     

Allelopathic interactions between plants. Multi site action of allelochemicals

Allelopathy is defined as mechanism of plant-plant, plant-microorganisms, plant-virus, plant-insect, and plant-soil-plant interactions mediated by plant- or microorganism-produced chemicals released to the environment. The majority of allelochemicals are secondary metabolites and among others belong to terpenoids, phenolic compounds, organic cyanides and longchain fatty acids. The action of allelochemicals in target plant is diverse and affects a large number of biochemical reactions resulting in modifications of different physiological functions. Thus the results of allelochemical action can be detected at different levels of plant organization: molecular, structural, biochemical, physiological and ecological. Enzyme activities, cell division and ultrastructure, membrane permeability, ion uptake and as a consequence plant growth and development are modified by allelochemicals. Significant effects on photosynthesis and respiration are the best-characterized results of allelopathic interactions. Moreover allelopathic compounds seem to induce a secondary oxidative stress expressed as enhanced free radical production and induction of cellular antioxidant system. Plant survival under allelopathy stress conditions depends on plant defense leading to allelochemical detoxication, the process which may go on in parallel to cell defense reaction to oxidative stress. The article presents some aspects of the current knowledge regarding mechanisms of the allelopathy phenomenon. The allelopathy is a complex problem, thus comprehensive understanding of allelochemical mode of action requires further investigation and still remains an open question.     

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.     

低钾胁迫对水稻(Oryza sativa L.)化感潜力变化的影响

研究以国际公认的化感水稻P1312777和非化感水稻Lemont为供体,稗草（Echinochloa cru-galli L.）为受体,采用稻／稗共培体系,研究低钾胁迫对水稻化感潜力变化的影响及其机制。受体稗草的形态指标分析结果表明,低钾胁迫促使化感水稻P1312777对共培稗草的根长、株高和干重的抑制率均升高,增幅远大于非化感水稻Lemont。受体稗草生理生化指标分析结果表明,低钾胁迫下化感与非化感水稻对受体稗草保护酶系（SOD、POD、CAT）及根系活力的抑制作用增强,但化感水稻P1312777比非化感水稻Lemont的抑制程度大,且达极显著差异。实时荧光定量PCR分析结果表明,低钾胁迫下,化感水稻P1312777根部与叶部中酚类代谢的关键酶——苯丙氨酸解氨酶、肉桂酸-4-羟化酶、羟化酶、O-甲基转移酶的基因均上调表达,而非化感水稻根部相应酶均下调表达,叶部除苯丙氨酸解氨酶上调,其余酶也下调表达。而萜类代谢途径关键酶——HMG—CoA还原酶、角鲨烯合酶、单萜烯环化酶、倍半萜烯环化酶、二萜烯环化酶的基因,在两种水稻根部中呈现出相同或相似的表达方式（上调或下调）,即HMG—CoA还原酶上调表达,角鲨烯合酶、单萜烯环化酶、倍半萜烯环化酶、二萜烯环化酶下调表达;而在水稻叶部,非化感水稻Lmont相应酶基因表达方式仍然不变,化感水稻P1312777除了角鲨烯合酶下调表达,其余4个酶均上调表达。水稻根系分泌物中酚类物质的HPLC分析结果表明,低钾胁迫下,化感水稻P1312777根系分泌物中,所检出的酚酸类物质总量是正常营养条件下的2．30倍,而非化感水稻Lemont则是正常营养条件下的0．91倍。综合分析认为低钾胁迫下,化感水稻P1312777抑草能力增强主要是由于酚类代谢途径关键酶基因表达上调,导致酚类代谢途径旺盛,分泌出更多的酚类物质,进而破坏受体稗草保护酶系统,抑制了稗草的正常生长。