化感作用的研究意义及发展前景

对化感作用在生态学、林业、农业等领域的理论及实践意义进行综述与探讨,并分析了其今后的发展方向.化感作用有助于更加合理地解释生态系统中植物组成与分布、群落演替、协同进化和生物入侵等现象;在林业生产的森林更新、混交林培育中有时会起到决定性作用;在农业上,单作、轮作、覆盖等各种种植方式均受化感影响,此外,一些化感物质可用作杀虫剂和除草剂,从而减轻对环境的污染水体中同样存在化感作用.培育新的抗虫害、抑草品种,分离、鉴定新的化感物质,深入揭示化感作用的机制,是今后化感作用的研究重点.     

连作花生土壤中酚酸类物质的检测及其对花生的化感作用

研究了南方红壤区不同连作年限花生土壤中酚酸物质的种类、含量,及其对花生生长的影响。结果表明:连作花生土壤中对羟基苯甲酸、香草酸和香豆酸随着连作年限的增加而增加,连作10a后3种酚酸总量达11.09mg·kg-1干土,显著高于连作3a和6a的土壤;而土壤中香豆素和苯甲酸含量比较低,且变化没有规律。所有酚酸处理组对花生幼苗的株高和根长表现出抑制作用,对花生幼苗地下部的干鲜重均表现出"低促高抑"的特点。香草酸和香豆酸处理组对花生幼苗地上部的干鲜重表现出"低促高抑"的特点,其他处理组均表现出抑制作用。花生幼苗根系活力随着酚酸处理浓度的增加而降低,花生幼苗的超氧化物歧化酶活力(SOD)、过氧化物酶活力(POD)、丙二醛含量(MDA)则随着酚酸浓度的增加而增加。与只用茄腐镰刀菌孢子悬液浸泡花生种子的对照相比,加入酚酸后,花生种子的病原菌的感染率随着酚酸浓度的增加而增加,发芽率则随着酚酸浓度的增加而下降。以上结果说明,酚酸物质可以抑制花生幼苗的生长和提高花生的发病率,可能是因为酚酸物质破坏花生细胞膜的完整性而使病原菌入侵,影响花生生长,产生连作障碍。     

Growth response of maize seed-borne fungi to cereal phenolic acid mixtures

Phenolic acids (PAs) are potential antifungal agents of stored grain cereals. Previous studies have mostly focused on the action of single compounds, consequently providing limited information on their effect as mixtures. We tested the hypothesis that higher phytochemical diversity and concentration of phenolic acids provide better defense against pathogenic fungi of cereals. Five maize seed-borne fungi with different degrees of specialization as cereal pathogens were exposed in vitro to five phenolic acids found in cereal grains either alone or in combinations. We detected that the inhibitory effect of PAs depended on their concentration and the fungus specialization, but the tested hypothesis was not functional for any plant-fungal species relationship. Moreover, various PAs or PAs-mixtures were almost equally inhibitory against the fungal species. We also found that phytochemical diversity had a differential effect on the phytopathogens according to their degree of specialization. Thus, a high phytochemical diversity in high concentration would protect a plant against a fungal community, but not necessarily against a single-fungus species.     

Challenges,achievements and opportunities in allelopathy research

Abstract

Allelopathy is defined as the suppression of any aspect of growth and/or development of one plant by another through the release of chemical compounds. Although allelopathic interference has been demonstrated many times using in vitro experiments, few studies have clearly demonstrated allelopathy in natural settings. This difficulty reflects the complexity in examining and demonstrating allelopathic interactions under field conditions. In this paper we address a number of issues related to the complexity of allelopathic interference in higher plants: These are: (i) is a demonstrated pattern or zone of inhibition important in documenting allelopathy? (ii) is it ecologically relevant to explain the allelopathic potential of a species based on a single bioactive chemical? (iii) what is the significance of the various modes of allelochemical release from the plant into the environment? (iv) do soil characteristics clearly influence allelopathic activity? (v) is it necessary to exclude other plant interference mechanisms?, and (vi) how can new achievements in allelopathy research aid in solving problems related to relevant ecological issues encountered in research conducted upon natural systems and agroecosystems? A greater knowledge of plant interactions in ecologically relevant environments, as well as the study of biochemical pathways, will enhance our understanding of the role of allelopathy in agricultural and natural settings. In addition, novel findings related to the relevant enzymes and genes involved in production of putative allelochemicals, allelochemical persistence in the rhizosphere, the molecular target sites of allelochemicals in sensitive plant species and the influence of allelochemicals upon other organisms will likely lead to enhanced utilization of natural products for pest management or as pharmaceuticals and nutraceuticals. This review will address these recent findings, as well as the major challenges which continue to influence the outcomes of allelopathy research.     

A new phenolic acid from Zanthoxylum nitidum var. tomentosum (Rutaceae) and its chemotaxonomic significance

A new compound, nitomentosin (1), along with sixteen known compounds (2–17), were isolated from Zanthoxylum nitidum var. tomentosum (Rutaceae). The structure of compound 1 including absolute configurations was determined by detailed spectroscopic information (HRESIMS and NMR) and from the electronic circular dichroism (ECD) spectra. From the present investigation, compound 3 is a new natural compound although it has been reported previously as a synthetic substance, and compound 15 is found for the first time in a plant. All these compounds except 2, 5–10 and 12 were isolated from Z. nitidum for the first time. Furthermore, the chemotaxonomic significance of the isolated compounds is discussed.     

水稻化感作用及其生理生化特性的研究

选用具有强化感作用的6个水稻品种为供体,大田稗草为受体,研究了水稻化感作用及生理生化特性,结果表明,提高水稻叶片浸提液浓度,可以相应增强对稗草生长的抑制效果,这种抑制效果与杂草的种植密度呈负相关;化感水稻叶片浸提液能显著抑制物质稗草体内超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的活性,从而影响其生长;苯丙氨酸氨解酶（PAL）的活性大小与酚类物质的含量吴正相关;多种酚类物质的化感作用之间可能是增效的,也可能是拮抗的。     

蕨类植物的化感作用及其对生物多样性的影响

植物化感作用是植物通过向环境中释放化学物质从而对同种植株和繁殖体或与其他植物之间产生的直接或间接、有益或有害的作用,它影响植物分布、群落形成与演化、作物间作等,与生物多样性保护以及农林和园艺生产实践关系密切,在国际上受到越来越多的关注。但国内这方面的研究起步相对较晚,研究范围有限,对蕨类植物化感作用的报道更少。本文系统介绍了蕨类植物化感作用的研究进展,包括蕨类植物种内的化感作用(即自毒效应)、常见的蕨类植物种间的化感作用(即孢子体对配子体的化感作用和配子体对配子体的化感作用)及蕨类植物对种子植物的化感作用(蕨类植物可通过化感作用与种子植物争夺更多的资源和生长空间)。还介绍了种子植物对蕨类植物的化感作用(主要表现为抑制作用)以及蕨类植物化感作用与动物侵食、微生物侵染的关系,研究发现昆虫侵食能增强或减弱蕨类植物的化感作用,微生物的活动可能增强某些蕨类植物的化感作用。本文从上述不同角度说明蕨类植物化感作用对生物多样性的影响,希望有助于促进我国学者对该领域的深入研究。     

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。     

植物化感作用的机理、影响因素及应用潜力

从化感作用与植物的叶水势、光合作用、呼吸作用、养分有效性、细胞分裂和代谢等方面的关系综述了化感作用的作用机理,同时就影响化感作用的主要因素进行了讨论。文章认为化感作用在科学构建种群结构、防除病虫草害、设计合理种植制度、提高肥水利用效率和秸秆还田利用率等领域具有较大的应用潜力。     

数学建模在生物化感及其赫米西斯(Hormesis)现象中的应用

简述了国内外对生物化感数学建模的研究近况,包括通过数学模型描述化感物质的赫米西斯(Hormesis)现象,化感作用在受体植物不同密度条件下的表达,植物残茬中化感物质的分解动态及受体植物的动态响应,环境中化感物质的动态变化规律及在植物-昆虫-天敌系统中的应用等。并对化感数学建模领域的先驱机理模型An-Hormesis模型,An-Liu-Johnson-Lovett模型,和An_Residue模型做了简介。     

植物功能型及其生态学意义

植物功能型是近年来在全球变化研究中引入的一个新的生态学术语,综 植物功能型概念的由来、划分植物及其生态学意义,用系统生物学的理论与方法理解植物功能型,并指出了植物功能型在全球变化研究中的意义。     

Unusual nonprotein imino acid and its relationship to phenolic and nitrogenous compounds in Copaifera

The unusual imino acid, N-methyl-trans-4-hydroxy-Lproline has been isolated from leaves of five species of the leguminous tropical tree Copaifera, and for the first time characterized by ¹H and ¹³C NMR and mass spectrometry. This imino acid can constitute up to 3% of the mature leaf dry weight and 10% of the nitrogen; it also constitutes 2–3 % of the dry weight of the seed. Preliminary feeding trials have shown it to be a very effective inhibitor of larval development of the seed-feeding bruchid beetle Callosobruchus maculatus and to have significant feeding deterrence of the leaf-feeding lepidopteran Spodoptera littoralis. Phenolic compounds, also known to affect herbivores adversely, comprise 6–10% leaf dry weight. However, the imino acid displayed a mean of 50% reactivity compared to standards commonly used in analysis of total phenolics by the Folin-Denis (F-D) assay [gallic acid, tannic acid and (+) catechin], thus resulting in a significant overestimate of phenolics by this assay. It is concluded that assessment of leaf food quality for herbivores of Copaifera by assays widely used for this purpose in ecological studies, such as F-D for phenolics and Kjeldahl for total nitrogen content, give some misleading results.     

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。     

Pyruvate decarboxylating action of L-cycloserine. The significance of this in understanding its metabolic inhibitory action

We present evidence which demonstrates that L-cycloserine, structural analog of L-alanine, which is known to be an effective aminotransferase inhibitor, is also a potent inhibitor of cellular pyruvate metabolism. This effect was found to be related to its almost instantaneous action in decreasing pyruvate concentrations in a dose-dependent manner. 1H nuclear magnetic resonance studies clearly demonstrate that the irreversible removal of pyruvate induced by L-cycloserine is caused by the decarboxylating action of the latter. Pyruvate disappearance induced by L-cycloserine can be stoichiometrically accounted for as acetate. The process does not involve any chemically detected transformation of L-cycloserine. These observations lead to two main considerations regarding the known action of L-cycloserine. First, its inhibitory effect on gluconeogenesis from lactate could be explained only on the basis of its ability to reduce pyruvate availability with no apparent need for transaminase inhibition. Second, its ability as a transaminase inhibitor should be reconsidered in view of its potent decarboxylating action on pyruvate and probably other oxoacids.