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.     

水稻化感作用研究综述

主要对水稻化感现象发现,化感生物检测,化感物质分离和鉴定,化感种质资源等方面的研究进展了系统的综合论述,在此基础上,进一步对化感作用研究中的主要问题,例如;生物检测手段,化感作用利用途径等进行了分析。并对我国的化感作用研究的存在问题及发展方向作出了论述。     

苜蓿化感作用研究进展

苜蓿是一种优良的多年生豆科牧草 ,具有多重生态功能 ,在世界范围内广泛种植。苜蓿在第 2～ 4年后产量逐渐下降 ,而且种过苜蓿的土壤 ,间隔较短时间再种苜蓿 ,很难建植成功。许多研究表明 ,苜蓿体内含有的一些水溶性化学物质不仅能够对其产生自毒作用 ,而且也能对其他植物具有化感作用。本文综述了苜蓿化感作用研究进展 ,包括苜蓿中主要的化感物质、影响苜蓿化感作用的因素、苜蓿化感作用的应用三个方面。同时就苜蓿化感作用今后的研究重点提出一些看法和展望。     

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     

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。     

大量元素胁迫下南瓜化感作用研究

研究采用水培实验、生物测试及室内分析相结合的方法,研究在不同大量元素(N、P、K、Ca、S、Mg)营养胁迫下幼苗期南瓜根系分泌物及其提取物对南瓜幼苗生长的化感作用。结果表明：南瓜具有自毒作用,不同大量营养元素胁迫对其胚根和胚芽生长均产生了抑制作用。不同的营养条件对其根系分泌物的影响不同,营养元素的合理搭配可以减轻自身的自毒作用。南瓜根系分泌物经乙酸乙酯提取的活性有机物埘南瓜胚根牛长亦表现出抑制作用,且抑制作用程度较大。南瓜幼苗期根系十物质水浸液巾存在着抑制南瓜幼苗生长的化感物质：筛选出南瓜根系分泌物对自身幼苗生长产生抑制作用最弱的大量元素水平优化组合,为南瓜的营养胁迫机理提供依据。     

浮游植物的化感作用

生物化感作用研究是近年来兴起的交叉学科,是化学生态学研究的重要领域。研究水域浮游植物化感作用对了解浮游植物之间、浮游植物与其他生物之间的相互作用及作用机理具有重要意义,对了解赤潮和水华的发生机制及其生态控制等具有非常重要的作用。综述了海洋和湖泊浮游植物化感作用和化感物质的内涵,讨论了水体浮游植物化感作用的特点、研究化感作用的基本方法、化感物质的种类以及影响化感物质作用的生物和非生物因素,详细介绍了浮游植物化感物质的作用机理以及逃避和拈抗化感作用的方式,同时对目前研究的热点问题及未来研究的方向做了简要概述。     

豚草的化感作用研究

本文研究了在我国东北地区广泛蔓延的菊科杂草－－豚草对大豆、玉米、小麦、水稻的化感作用,实验针对豚草的挥发物、茎叶和根的淋溶物、根区土壤水浸液等的化感活性进行了研究,研究发现豚草的挥发物对大豆和玉米的种子萌发有一定抑制作用,根区土壤对农作物无明显的作用;茎叶部分的水浸液对几种农作物的种子萌发和幼苗的幼根伸长有明显的抑制作用,同时使根系形态发生较大的变化,根系的水浸液对作物的幼芽伸长有一定的促进作用。     

植物化感作用研究进展——以抑制铜绿微囊藻生长为例

水体富营养化引起的藻华问题依旧是当前世界共同面对的难题,其中植物释放化感物质应对藻华是高效低耗的手段,受到国内外研究者的青睐.综述了不同水生植物和陆生植物对铜绿微囊藻(Microcystis aeruginosa)的生长影响,总结了抑制铜绿微囊藻的植物种类、研究方法、化感作用效果以及化感作用机理,归纳了各种植物的化感作...     

再力花地下部水浸提液对几种水生植物幼苗的化感作用

采用砂培法研究了不同浓度再力花地下部水浸提液对荇菜、苦草、水田芥、芦苇和黄菖蒲幼苗的生长、光合速率、根系活力、叶绿素含量以及抗氧化保护酶活性的影响,并采用气相色谱-质谱(GC-MS)联用技术对再力花地下部水浸提液的化学成分进行了分析。结果表明:再力花地下部水浸提液对荇菜、苦草、水田芥、芦苇和黄菖蒲5种水生植物幼苗生长有明显的影响,其中使用50mg干重/mL再力花水浸提液处理5种水生植物幼苗,对其生长指标有着极显著的抑制作用(P<0.01),苦草、水田芥和黄菖蒲的净光合速率分别降低69.0%、63.7%和73.5%,荇菜、苦草、水田芥和黄菖蒲幼苗根系活力分别降低67.3%、65.4%、52.2%和46.7%,5种水生植物幼苗叶绿素含量分别下降59.7%、71.2%、35.2%、50.0%和76.5%。当处理浓度为5mg/mL时,对5种水生植物幼苗体内过氧化物酶(POD)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性有显著的促进作用;当浓度为50mg/mL时,对5种水生植物幼苗体内POD、SOD和CAT有显著的抑制作用,丙二醛(MDA)含量增加。分析显示,再力花地下部水浸提液中主要含有愈创木酚(78.93%)、邻苯二甲酸二丁基酯(7.13%)、邻苯二甲酸二乙氧基乙酯(1.48%)、香豆满(1.09%)、邻苯二甲酸二乙酯(0.98%)、松油醇(0.70%)、吲哚(0.65%)、二丁基羟基甲苯(0.64%),合计占到总量的91%以上。     

水生植物引种的生态安全评价

随着水生植物的大量应用,水域环境的生态安全越来越受到关注。水生植物入侵具有一定的生物学、区系地理、生态位和生境特征,对水生植物的生态安全评价可在一定程度上防止水生植物引种的盲目性。该文针对来自水生外来入侵植物的生态安全威胁,分析了水生外来入侵植物的入侵特征及其危害,提出了水生植物引种的生态安全评价的内容、程序、指标体系和方法。     

Synthesis and release of cyclic adenosine 3':5'-monophospliate by aquatic macrophytes

Tissues from the aquatic macrophyte species Scirpus subterminalis, Najas flexilis, Ceratophyllum demcrsum, Potamogeton zosteriformis, and Nuphar advena contain cAMP in quantities similar to those reported in algae. Scirpus, Najas , and Ceratophyllum released cAMP into the extracellular media in quantities which varied interspecifically and intraspecifically in differing media. Macrophytic release of cAMP may be an important source of dissolved cAMP in lakewater.     

Ecogeographical tolerance range variation in aquatic macrophytes

A portion of central Canada (area B) and a smaller, soft-water area within it on the Precambrian Shield (area A) were surveyed for aquatic macrophytes in relation to eight water chemistry parameters. pH, total dissolved solids and total alkalinity appeared to be the three most important factors correlated with macrophyte distribution. T-tests indicated that species for which water chemistry affinities were not discrepant in areas A and B could be identified as specialized or unspecialized plants with respect to area A. Other species behaved quite differently in the two areas. In most cases for pH and dissolved inorganics macrophytes showed lower mean values and lower upper tolerance range limits in area A than in area B, reflecting the prevailing water chemistry values in the two areas. These results suggested that adaptation had occurred in one or both sets of populations. A number of interspecific associations were demonstrated in area A, many of which coincided with similarities in water chemistry affinities.     

Seasonality/aseasonality of aquatic macrophytes in Southern Hemisphere inland waters

The term aseasonality is used in this paper to describe environmental conditions which either lack annual seasonal change or have periodicities of change which are longer or shorter than the seasons. Environmental factors act on plants either as stresses or disturbances and changes in environment can signal the onset of conditions which are favourable or unfavourable to plant growth and reproduction. Plant life-histories are thus adapted to these environmental factors and respond to them with both seasonal and aseasonal periodicities, depending on their manner of occurrence and effect on the plants. A review of pertinent studies from the Southern Hemisphere shows that plants of the same life-form (submerged, floating, emergent) might differ in the types of adaptation and response to environmental conditions according to latitude but that the periodicity of response could be seasonal or aseasonal regardless of latitude. The concept of seasonality versus aseasonality is therefore misleading and an oversimplification of the variety of periodicities with which the environment acts on plant genotypes. Limnological principles of the Northern Hemisphere are applicable to aquatic macrophytes in the Southern Hemisphere but there is a particular need for research into the effects of biotic variables and water level fluctuations on aquatic plants and communities in the latter.     

Niche congruency of aquatic macrophytes in central North America with respect to 5 water chemistry parameters

The occurrences of aquatic macrophytes were studied at 430 sites in central North America with respect to total alkalinity, chloride, sulphate, molybdenum reactive phosphorus and dissolved organic matter. Mean niche positions were calculated for the combination of 5 parameters by comparing mean values for each species using agglomerative hierarchical cluster analysis. Overall niche relations were examined by calculating and summing the amount of overlap in the observed ecological tolerance ranges for the 5 parameters for each species pair, and applying cluster and principal component analysis. The results showed that the macrophytes occupied a broad spectrum of niches, ranging from species found at low inorganic concentrations and narrow tolerance ranges, to species occupying broad ranges in the study area. Species with similar overall niches differed with respect to their mean niche positions, and vice versa. Macrophytes with similar niche positions may use a number of strategies to reduce interspecific competition.     

东太湖水生植物群落结构的演变及其沼泽化

2002年东太湖水生植被调查结果表明,沉水植被和浮叶植被是该湖水生植被的主要生态类型,分布面积分别占全湖总面积73.6%和18.3%。东太湖水生植被主要有9个群丛,其中沉水植被主要的5个群丛是伊乐藻(外来种)群丛、金鱼藻群丛、伊乐藻 微齿眼子菜群丛、菜-伊乐藻 微齿眼子菜群丛、苦草 竹叶眼子菜 黑藻群丛,其分布面积分别占东太湖植被总面积的30.7%、17.2%、16.7%、15.8%、9.3%。随着对东太湖的不断改造和资源的不断利用,20世纪60年代东太湖人工种植沼泽植被菰群丛,20世纪80年代初环湖水陆交错带被围垦而芦苇群丛消失,微齿眼子菜替代竹叶眼子菜而占据东太湖40%的水面。近10a来,东太湖网围养蟹迅速发展,占全湖总植被面积25.6%的沼泽植物——菰群丛及其占40%的微齿眼子菜群丛被清除,外来种伊乐藻和无根植物金鱼藻分布面积达90%的湖区。东太湖水生植被由20世纪50年代的原生演替到现在的次生演替,群落演变激烈,同时东太湖沼泽化进程加剧。     

Decomposition dynamics of aquatic macrophytes in the lower Atchafalaya, a large floodplain river

Decomposition of aquatic macrophytes can considerably influence carbon cycling and energy flow in shallow freshwater aquatic ecosystems. The Atchafalaya River Basin (ARB) is a large floodplain river in southern Louisiana that experiences a seasonal floodpulse and is spatially composed of a mosaic of turbid riverine and stagnant backwater areas. During two seasons, winter and fall of 1995, we examined decomposition of four common aquatic macrophytes in the ARB: water hyacinth (Eichhornia crassipes), arrowhead (Sagittaria platyphylla), coontail (Ceratophyllum demersum) and hydrilla (Hydrilla verticillata). To determine decay rates, we used litter bags of two mesh sizes (5 mm and 0.25 mm) and analyzed data with a single exponential decay model. Analysis of decay rates established several trends for aquatic macrophyte decomposition in the ARB. First, macrophytes decayed faster in fall than winter due to the effect of increased temperature. Second, macroinvertebrates were the primary decomposers of macrophytes in riverine sites and microbes were the primary decomposers in backwater areas. These trends may have been related to decomposer-habitat interactions, with well-oxygenated riverine sites more hospitable to invertebrates and backwater areas more favorable to microbes because of high organic inputs and reduced flow. Decay rates for macrophytes, ranked from slowest to fastest, were E. crassipes<S. platyphylla<C. demersum<H. verticillata. Slower decomposition of E. crassipes was probably a result of microbial inhibition by the waxy-cutin outer layer and low nutritional value. The accelerated decomposition of C. demersum and H. verticillata was most likely a function of the large surface area of the highly dissected leaves. Macroinvertebrate numbers were twice as high in riverine sites compared to backwater sites. In the winter, amphipods Gammarus spp. and Hyallela azteca composed a large percentage of the total density on detritus. In the fall, Caenis sp. was prevalent in the backwater habitat and dipterans were abundant in the riverine site. We investigated the microbial component involved in the decomposition of E. crassipes and S. platyphylla and found that the highest microbial respiration rates occurred early in the winter at the backwater site. Bacterial density in the winter on E. crassipes and S. platyphylla averaged 1.4×10⁶ cm^-2 after two days and decreased to 2.0×10⁵ cm^-2 after 28 d. Our results emphasized the importance of the microbial community in the decomposition of macrophytes in the ARB, especially in backwater habitats and in the early stages of decay.     

The effects of lime addition on aquatic macrophytes in hard water: in situ and microcosm experiments

1. Aquatic macrophytes are abundant in ponds and canals that are constructed in semi‐arid regions for water storage and conveyance, as well as in lakes that are culturally enriched. 2. Addition of Ca(OH)₂ to two hardwater ponds at 250 or 275 mg L^–1 caused an immediate eradication of submersed aquatic plants. Although these ponds are well‐buffered (alkalinity: 2.57–3.94 mequiv L^–1; pH: 8.1–9.0), lime addition caused an immediate increase in pH of 0.2–3 units. 3. Application of 135 mg L^–1 Ca(OH)₂ for 24 h or 210 mg L^–1 Ca(OH)₂ for 65 h to two irrigation canals had no effect on macrophyte biomass at the lower concentration and duration, but resulted in the elimination of aquatic macrophytes 1 month after the higher concentration, longer duration treatment. 4. Unlike the macrophyte control achieved following application of 210–275 mg L^–1 Ca(OH)₂ to ponds or canals, microcosm experiments in which lime formulation [slaked lime (Ca(OH)₂), calcite (CaCO₃), or a 1 : 1 mixture] and concentrations (up to 1500 mg L^–1) were manipulated failed to elicit a consistent change in macrophyte biomass. Macrophytes in microcosms treated for the short‐term (23–33 days) with ≥ 200 mg L^–1 Ca(OH)₂ or a mixed Ca(OH)₂/CaCO₃ formulation always lost pigmentation, but biomass was not consistently reduced. 5. Declines in macrophyte biomass following treatment of ponds and canals may have been triggered by a short‐term rise in pH which, in these relatively warm (22–23 °C) alkaline (2.28–3.94 mequiv L^–1) systems, would have resulted in low concentrations of free CO₂ and bicarbonate for photosynthesis.     

A small dredge for sampling aquatic macrophytes

A small dredge for sampling of aquatic macrophytes in shallow lakes, ponds and rivers is described. The dredge consists of a crown-like stainless steel vessel, disk and legs. The total dredge weight is 550 g. The dredge is useful for sampling higher plants, water ferns, mosses, liverworts and large algae, and for sampling soft sediments.