The potential benefits from cultivar specific red clover -potato crop rotations

The aim of this study was to determine if endophytic bacteria could contribute to cultivar specific interactions between red clover (Trifolium pratense L.) and potatoes (Solanum tuberosum L.) in crop rotations. Endophytic bacteria were isolated from the roots of four red clover cultivars (AC Charlie, Altaswede, Marino and Tempus) grown in the field. Populations of bacteria from each cultivar were similar. The most abundant genus was Rhizobium, but species of Curtobacterium, Pseudomonas, and Xanthomonas were common to all cultivars. Plantlets of two potato cultivars, Russet Burbank and Shepody, were inoculated individually with the seven bacterial isolates most frequently recovered from each red clover cultivar, and grown in Magenta vessels for 6 wk. Significant differences were found for plant height, and wet weights of roots, shoots and their total. Potato cultivars differed for root wet weight only, while red clover cultivar, as a source of bacteria, had a significant effect on all traits except plant height. Differences among bacteria were significant for all traits except shoot wet weight. There was a significant interaction of potato cultivar by red clover cultivar. The potato cultivar Russet Burbank did best with bacteria from the red clover cultivar, Marino; and Shepody, with bacteria from Altaswede.     

植物化感作用的研究方法及影响因素

介绍了植物化感作用研究的几种生物测定方法,并对影响化感作用效应的因子进行了论证     

三七自毒与化感作用初步研究

采用生物测定方法,对三七的自毒与化感作用进行初步研究。结果表明:(1)三七种子萌发过程中的自毒作用随其播种密度不同而有一定差异,但无明显规律性。三七种子萌发过程中的分泌物对油菜生长具有化感作用,主要表现为对油菜种子发芽率、发芽指数及苗高的抑制效应;(2)三七水浸液对不同受体植物的化感作用不尽相同,对小麦主要表现为对苗鲜重、苗干重、根鲜重、苗高及须根数有不同程度的促进或抑制作用;对油菜则表现为对其种子发芽率具有抑制作用,而对苗鲜重、苗干重、根鲜重、最长根长具有促进作用;(3)三七存在明显的化感自毒作用,其自毒物质可能为影响其连作的一个重要因素。     

Coumarin inhibits the growth of carrot (Daucus carota L. cv. Saint Valery) cells in suspension culture

We used a carrot (Daucus carota L. cv. Saint Valery) cell suspension culture as a simplified model system to study the effects of the allelochemical compound coumarin (1,2 benzopyrone) on cell growth and utilisation of exogenous nitrate, ammonium and carbohydrates. Exposure to micromolar levels of coumarin caused severe inhibition of cell growth starting from the second day of culture onwards. At the same time, the presence of 50 mumol/L coumarin caused accumulation of free amino acids and of ammonium in the cultured cells, and stimulated their glutamine synthetase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphoenolpyruvate carboxylase activities. Malate dehydrogenase, on the other hand, was inhibited under the same conditions. These effects were interpreted in terms of the stimulation of protein catabolism and/or interference with protein biosynthesis induced by coumarin. This could have led to a series of compensatory changes in the activities of enzymes linking nitrogen and carbon metabolism. Because coumarin seemed to abolish the exponential phase and to accelerate the onset of the stationary phase of cell growth, we hypothesise that such allelochemical compounds may act in nature as an inhibitor of the cell cycle and/or as a senescence-promoting substance.     

酚酸类物质的化感作用研究进展

酚酸类物质是普遍存在于高等植物组织并与植物生长密切相关的次级代谢产物。几十年来,人们对酚酸类化合物的认识逐渐加深,但关于其在生物学、生态学以及农业上的作用机制仍不是很清楚。因此,进一步了解这些生物分子将有助于生态系统的维持与保护。重点介绍了酚酸类物质的来源及化感作用,微生物对酚酸类物质的降解机理,代谢途径及相应分子水平的研究,指出了酚酸类物质研究中存在的问题,同时展望了酚酸类物质的研究方向与前景。     

Differential sensitivity of green algae to allelopathic substances from Chara

Three short-term laboratory experiments were conducted to investigate allelopathic effects of a mixture of Chara globularis var. globularis Thuillier and Chara contraria var. contraria A. Braun ex Kützing on three different green algae. Single phytoplankton species were exposed to filtered water originating from charophyte cultures. Phytoplankton growth was monitored by determination of chlorophyll concentrations in batch cultures. The change in chlorophyll concentration during the experiments was analysed with a logistic growth model, resulting in an estimate of the exponential growth rate and the duration of the lag phase of the single green algae. The results indicate allelopathic effects of Chara on the growth of the green algae Selenastrum capricornutum Printz and Chlorella minutissima Fott et Nováková, whereas Scenedesmus obliquus (Turpin) Kützing did not seem to be affected. The exponential growth rate of S. capricornutum decreased 7% in the presence of water from a charophyte culture, while the growth rate of C. minutissima decreased with 3%. The allelopathic effect of Chara did not increase when the green alga C. minutissima was P-limited. The effect of Chara was different when young sprouts were used. With young sprouts the duration of the lag phase of C. minutissima was extended (25%), whilst for old plants the growth rate of this green alga decreased. Although the inhibiting effect of charophytes on specific phytoplankton species is rather small, the differential sensitivity of the species to Chara might influence the composition and biomass of phytoplankton communities in the field.     

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.     

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。     

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。     

人工群落中苗期紫茎泽兰的化感作用和对光环境的适应

在有、无活性炭的条件下分别构建紫茎泽兰（Ageratinaa denophora）与4种受体植物——飞机草（Chromolaena odorata）、鬼针草（Bidenspilosa）、胜红蓟（Ageratum conyzoides）和兰花菊三七（Gynura sp.）混种的人工群落,研究了群落中紫茎泽兰的化感作用和对群落光环境的适应,探讨了化感作用和光适应特性与其入侵性的关系。结果表明,活性炭处理对4种受体植物的生长、生理特性影响不显著,说明苗期紫茎泽兰化感作用不明显,推测入侵初期化感作用不是紫茎泽兰排挤本地种的主要原因。4种受体植物可以通过化感作用对紫茎泽兰产生某些影响,但群落的光环境对其影响更大。紫茎泽兰能很好地适应群落中不同的光环境。苗期紫茎泽兰处于群落下层,叶片受光指数低,此时它能长期忍耐并缓慢生长;随着叶片受光指数的升高,其最大净光合速率、超氧化物歧化酶活性、叶绿素a／b比、总生物量、总叶面积、地茎、叶片数和分支数升高,比叶面积和比茎长降低,这有利于它维持叶片能量平衡并导致对邻近植物的严重遮荫。紫茎泽兰强的光适应能力、强光下对其它物种的遮荫效应与其入侵性密切相关。