Plant allelochemicals inhibit the growth and colony formation of Microcystis

Genus Microcystis is the most common dominant species of bloom-forming cyanobacteria.Growth and colony formation are critical processes for the occurrence of Microcystis blooms.To identify allelochemicals that can inhibit the growth and colony formation of Microcystis,Microcystis aeruginosa was cultivated and treated with various concentrations of gramine,catechol,berberine,and sanguinarine in laboratory.Results indicate that the growth,colony formation,and extracellular polysaccharides(EPS)content of Microcystis were significantly inhibited when treated with gramine,catechol,and berberine in appropriate concentrations at high iron level(6.8 mg/L).Microcystis growth was inhibited and colony formation and EPS content were promoted when treated with sanguinarine at high iron level.These findings suggest that cyanobacterial blooms can be controlled by regulating the input of gramine,catechol,and berberine.Furthermore,this study revealed that plant allelochemicals could affect the growth and morphology of algae in aquatic ecological restoration,which may be potentially important for improving water quality.

Antialgal Activities of Allelochemical Extracts from 3 Terrestrial Plant Species

[Objective] The aim was to study the antialgal activities of allelochemical extracts from three terrestrial plant species.[Method] The allelochemicals were extracted from the leaves of Magnolia grandiflora,Sophora japonica f.pendula and Buxus sinica （Rehd.et Wils.） Cheng by alcohol extraction,n-hexane,ethyl acetate and n-utanol phase.Furthermore antialgal activities of all components were determined.[Result] The active substances of M.grandiflora mainly existed in n-hexane and n-butanol phases.The active substances of S.japonica mainly existed in n-hexane phase,while the active substances of B.sinica mainly existed in ethyl acetate and aqueous phase.All the active substances showed significant antialgal activity （50% inhibition） after culture for 1 d except aqueous phase of B.sinica.In addition,inhibition rates of the tested phases increased with the increasing of culture duration and testing concentrations.The inhibition rates were over 90% against the growth of M.aeruginosa after culture for 7 d.The n-hexane and n-butanol phases of M.grandiflora exhibited the best antialgal activity,over 96% inhibition rate at the concentration of 25 μg/ml,which was significantly higher than those of the other components,furthermore it could cause shrinkage and obvious surface inanition of Microcystis aeruginosa.[Conclusion] The n-hexane and n-butanol phases of M.grandiflora have the best inhibition activities on the growth of Microcystis aeruginosa,so they are worthy of further study.

Allelochemicals and allelopathy from microorganisms in wheat rhizosphers

Allelochemicals from fungi and bacteria in wheat rhizosphere,as well as their allelo- pathic effects on wheat and maize have been conducted.Fungi and bacteria were incubated at tem- perature 28-30℃.The extracts were tested for bioassay.Some samples identified to be responsi- ble for allelopathy have been determined by GC-MS.Some chemicals identified were selected to test again their bioactivity.The results showed that acidic extracts were more toxic to germination of wheat and maize seeds(statistic significant difference P<0.01 or P<0.05)and basic extracts were less toxic and stimulated effects on germination in some cases.A good relationship has been observed between the data of chemical analysis and bioassay. A wide variety of chemicals such as phenolic acids,organic acids,aldehydes,alcohol,ke- tones,nitrogen-containing chemicals,were identified by GC-MS.Some phenols and organic acids were identified to be inhibit and nitrogens-containing compounds were to be stimulate to germina- tion of seeds and extension of root and shoot of wheat and maize.

Allelochemicals of Panax notoginseng and their effects on various plants and rhizosphere microorganisms

Panax notoginseng(Araliaceae)is an important ginseng herb with various health benefits and a history of cultivation in southwestern China over 400 years.In recent years?.notoginseng has faced serious continuous-cropping obstacles due to its large-scale cultivation.In this study,we aim to explore the allelochemicals of P.notoginseng and their interactions with various plants and rhizosphere microor-ganisms.The chemical constituents of the soil cultivated with 3-year-old P.notoginseng were studied by column chromatography,spectroscopic and GC-MS analyses.We identified 13 volatile components and isolated six triterpenes(1-4,6-7)and one anthraquinone(5).Compounds 1-7 were tested for their effects on seed germination and root elongation in P.notoginseng,corn,wheat,turnip,water spinach and Arabidopsis thaliana.We also examined the effect of compounds 1-7on the growth of ten rhizosphere microorganisms of P.notoginseng.At a concentration of 1.0 ug mL',compounds 3 and 5-7 caused the death of P.notoginseng root cells and compounds 2,6 and 7 induced the death of root cells of A.thaliana.Compounds 1-5and 7 inhibited elongation of A.thaliana root tip cells at a concentration of 10.0μg mL^-1.Moreover,at a concentration of 0.1 mg mL^-1,compounds 3,4,6 and 7 inhibited the growth of probiotics and promoted the growth of pathogens of P.notoginseng.These results suggest that these isolated ursane-type triterpenoid acids and anthraquinone are potential allelochemicals that contribute to continuous-cropping obstacles of P.notoginseng.

The impact of allelochemicals on the differential expression of symbiotic bacteria in cotton aphids

Insects have developed a good adaptive mechanism in response to environmental stresses in the long-term evolution. They have developed a helpful metabolism system to resist plant allelochemicals. Insects also harbor different kinds of symbiotic bacteria, which provide them a competitive advantage. Here, using cotton aphid as an example, we investigated the effects of four plant allelochemicals on the differential expression of symbiotic bacteria based on transcriptome data. We also studied the composition of symbiotic bacteria and function on pathway level in three kinds of aphids. We found that the bacteria have a significant role in resisting the plant allelochemicals stress and host plant selection by aphids. These results should be useful to investigate the environmental adaption mechanism of aphids in the view of symbiotic bacteria. These results would offer a new insight for improving strategy of aphids and developing new pest control systems.

Effects of allelochemicals on activity of nitrate reductase

Study on the effects of allelochemicals such as trans \|ferulic acid ( t \|FA), benzoic acid (BA) and p \|hydroxybenzoic acid ( p \|HA), isolated from decomposed wheat straw on the activity of nitrate reductase at different concentrations of allelochemicals and different pH is described. t \|FA (0.26, 2.58 and 5.15 mmol/L) and BA (4.09, 8.19 mmol/L) showed a certain inhibition to the activity of nitrate reductase. The highest inhibition rate was 18.40%, but BA (0.41 mmol/L) and p \|HA (0.36, 1.81 and 3.62 mmol/L) showed stimulation, the more strong stimulation rate was 15.80%. At pH 6 condition, the activity of nitrate reductase was stronger inhibited than pH 7 and pH 8, but the mixture of 3 allelochemicals at pH 6 showed a stimulation. The mixture, however, at pH 7 and pH 8 showed some inhibition. It was found that there was a relationship between production of NO\+-\-2 and transformation of NO\+-\-3.

Identification and Quantification of Allelochemicals from Selected Sweet Potato (<i>Ipomoea batatas</i>(L.) Lam.) Cultivars

Allelopathic compounds have the potential to inhibit the growth and development of other organisms in a diverse manner ranging from shifting nutrients and enhancing their growth to inflicting diseases. In addition, these compounds influence seedling growth and seed germination of various crops. The goal of this study was to identify and quantify different allelochemicals in various sweet potato cultivars through high-performance liquid chromatography techniques. Selected sweet potato slips (weight: 2.0 - 2.5 grams/slip) were propagated in separate glass tubes filled with 10.0 mL distilled water. Water extract from each glass tube was collected after 2, 4, and 6 weeks after transplanting (WAP) to identify and quantify allelochemical compounds by comparing their peaks with the retention time of standards. Results show that the concentration of allelochemicals in water extract was increased from 2 to 4 WAP but remained constant in the sixth week. Quantitative analysis revealed that the amount of chlorogenic acid was higher in all sweet potato cultivars compared to other allelochemicals. Some sweet potato cultivars, A5 and A39, exhibited higher allelopathy (18.28 - 19.37 ppm/slip) and reduced the height and biomass of Palmer amaranth the most due to the presence of increased concentration of combined allelochemicals, while other cultivars produced lesser allelochemicals (10.90 ppm/slip) and did not reduce the growth of the weed species. Allelopathic sweet potato cultivars high in chlorogenic acid production can effectively suppress Palmer amaranth with minimal dependence on chemicals to manage weeds and harmful pests under sustainable agricultural system.

Role of extracellular polymeric substances in resistance to allelochemical stress on Microcystis aeruginsosa and its mechanism

Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety.However,the suppression efficiency is affected inevitably by the extracellular polymeric substances(EPS)produced by cyanobacteria,and the knowledge about the roles of EPS in resistance to allelochemical stress is scarce.For the study,two typical anti-cyanobacterial allelochemicals were adopted to investigate the role of EPS in resistance to allelochemical stress on Microcystis aeruginosa.Results show that EPS was crucial in alleviating the toxicity of allelochemicals to algae,especially in stabilizing the metabolism and photosynthetic activity of algal cells.The aggregation rate of algal cells increased with the increase of EPS secretion,which alleviated the stress of allelopathy.Tryptophan proteins and humic acids in EPS provided a binding site for allelochemicals,and the EPS-allelochemicals complex were formed by chemical bonding.This study improved our comprehension of the role of EPS in algal inhibition by allelochemicals.

Effects of Two Potential Allelochemicals on the Photosystem II of Nitzschia closterium and Monostroma nitidum

In aquaculture,high-density seaweed farming brings higher economic benefits but also increases outbreaks of diatom felt.The effective control of diatom felt in high-density seaweed farming has always been a research hotspot.This study selected two potential allelochemicals 2-hydroxycinnamic acid and quinic acid to explore their effects on a diatom Nitzschia closterium and an economic seaweed Monostroma nitidum.The results showed that 2-hydroxycinnamic acid had better inhibitory effects than quinic acid on the growth,pigment content and photosynthetic efficiency of N.closterium.Their half-maximal inhibitory concentrations at 120 h(IC_(50–120 h))were 0.9000 and 1.278 mM,respectively.Additionally,these allelochemicals had limited inhibitory effects on the growth,pigment content and photosynthetic efficiency of M.nitidum before 24 h.To further explore the allelopathic effect of these chemicals,this study focused on the photosystem II energy fluxes of N.closterium.It was found that 3 mM 2-hydroxycinnamic acid could destroy the whole photosynthetic system by devastating the PSII reaction centre(RC)before 24 h;however,the same concentration of quinic acid could only down-regulate the electron transport efficiency by changing the effective antenna size of an active RC and downregulating the PSII reaction centre density.These experimental results are expected to provide a new strategy to control diatom felt blooms on the high-density seaweed farming areas.

The Study of Allelochemicals of the Melon Fly (Myiopardalis pardalina Bigot.)

This study describes the isolation, identification of allelochemicals of the melon fly (Myiopardalis pardalina Bigot.), using the GC-MS method. A food attractant has been identified and a method for the synthesis of its synthetic analogue has been developed. Also, a route for the synthesis of para pheromone, raspberry ketone, has been proposed.

覆膜对陇东旱地苹果根际土壤化感物质积累与真菌群落特征的影响

【目的】探究果园地膜覆盖对土壤化感物质及真菌群落的影响。【方法】以红富士苹果为研究对象,采用高效液相色谱技术和Illumina高通量测序技术探究了清耕(CK)、覆膜2年(2Y)、覆膜4年(4Y)和覆膜6年(6Y)对苹果树根际0~20 cm和>20~40 cm土层土壤理化性质、化感物质和真菌群落特征的影响。【结果】苹果根际土壤脲酶活性随着覆膜年限的延长而降低。土壤中主要的化感物质的含量总体上随着覆膜年限的延长呈现出降低的趋势。覆膜措施对苹果根际土壤中真菌群落特征具有显著的影响。土壤真菌群落的多样性随着覆膜年限的延长而增高,其中镰刀菌属丰度显著增加。综合对比,覆膜4年的苹果根际土壤中含水量及有机碳、微生物量碳、全氮含量显著增加,较CK分别增加了5.65%~15.00%、3.72%~8.29%、50.16%~64.31%和14.19%~31.44%。β-1,4-木糖苷酶、β-1,4-葡萄糖苷酶和纤维二糖水解酶的活性显著提高,较CK分别增高了78.71%~84.4%、89.01%~97.43%和83.45%~87.68%。并且在0~20 cm的土层中苹果根系的生长量显著提高。与CK相比,根系生物量、根表面积和根体积分别增加了489.84%、533.87%和542.39%。相关性分析结果表明,土壤脲酶、β-1,4-葡萄糖苷酶和香兰素是影响土壤真菌群落的主要环境因子。【结论】覆盖地膜可通过影响苹果根际土壤酶活性和微生物代谢活性,促进土壤碳循环,效果随覆膜年限而异,以覆膜4 a(年)最佳。同时覆膜年限的延长抑制了土壤中植物化感物质的积累,但覆盖年限过长会对土壤真菌群落结构产生不利的影响,因此在生产中,覆膜4 a为西北旱地苹果园适宜的连续覆膜年限。

酚酸类化感物质对根际土壤养分供应能力的影响

为探究酚酸类化感物质通过何种途径限制受体植物的养分吸收,以酚酸类物质中的对羟基苯甲酸(p-HA)和肉桂酸(CA)为化感物质,生菜和番茄为化感受体植物,采用盆栽控制实验,分析不同浓度p-HA和CA处理下生菜和番茄叶片中碳(C)、氮(N)、磷(P)养分含量及根际土壤中与C、N、P循环有关的土壤酶活性及微生物状况的变化。研究发现,随化感胁迫加剧,受体植物叶片C、N、P养分含量下降,生菜和番茄的根际土壤微生物生物量C、N、P含量和根际土壤中的蔗糖酶、淀粉酶、脲酶、蛋白酶、磷酸酶活性均随酚酸类化感物质浓度的增加呈下降趋势。结果表明,降低受体植物根际土壤微生物生物量C、N、P含量和降低受体植物根际土壤中与C、N、P元素循环有关的酶活性是酚酸类化感物质降低受体植物养分吸收的两条重要途径。

槲皮素的生物活性及应用研究进展

槲皮素是一种重要的黄酮类化合物,具有抗氧化、抗炎、抗癌、抗菌、抗病毒、预防与改善糖尿病、抗高血压、免疫调节等生物活性,在医药领域具有良好地应用前景,可以预防和治疗多种疾病,如炎症、癌症、糖尿病、高血压、自身免疫性疾病等。此外,槲皮素作为重要的植物次生代谢物还具有化感活性与植物保护作用,在农业领域也有很好地应用潜力,可以用来开发新型绿色除草剂或植物生长调节剂。但槲皮素存在水溶性与稳定性差、生物利用度低等缺点,严重限制了其在医药与农业领域的应用,将槲皮素负载至纳米材料上制备成槲皮素纳米颗粒可以克服上述槲皮素的缺点。作者就近几年国内外槲皮素生物活性及应用研究进展进行了综述,涉及了医药及农业领域,为后续槲皮素相关理论及应用研究提供参考。

Functional mechanism study of the allelochemical myrigalone A identifies a group of ultrapotent inhibitors of ethylene biosynthesis in plants

Allelochemicals represent a class of natural products released by plants as root,leaf,and fruit exudates that interfere with the growth and survival of neighboring plants.Understanding how allelochemicals function to regulate plant responses may provide valuable new approaches to better control plant function.One such allelochemical,Myrigalone A(MyA)produced by Myrica gale,inhibits seed germination and seedling growth through an unknown mechanism.Here,we investigate MyA using the tractable modelDictyostelium discoideum and reveal that its activity depends on the conserved homolog of the plant ethylenesynthesis protein 1-aminocyclopropane-1-carboxylic acid oxidase(ACO).Furthermore,in silico modeling predicts the direct binding of MyA to ACO within the catalytic pocket.In D.discoideum,ablation of ACO mimics the MyA-dependent developmental delay,which is partially restored by exogenous ethylene,and MyA reduces ethylene production.In Arabidopsis thaliana,MyA treatment delays seed germination,and this effect is rescued by exogenous ethylene.It also mimics the effect of established ACO inhibitors on root and hypocotyl extension,blocks ethylenedependent root hair production,and reduces ethylene production.Finally,in silico binding analyses identify a rangeof highlypotentethylene inhibitorsthatblock ethylene-dependent responseand reduce ethyleneproduction in Arabidopsis.Thus,we demonstrate a molecular mechanism by which the allelochemical MyA reduces ethylene biosynthesis and identify a range of ultrapotent inhibitors of ethylene-regulated responses.

单宁酸对豌豆蚜谷胱甘肽-S-转移酶活性与基因表达的影响

本研究通过测定单宁酸(2 g·L^(-1))处理豌豆蚜(Acyrthosiphon pisum) 48 h后体内谷胱甘肽-S-转移酶(GST)活性以及不同组织GST基因转录水平的变化,以明确单宁酸对GST活性以及基因表达的影响。结果表明:豌豆蚜取食单宁酸(2 g·L^(-1)) 48 h后,GST活性下降。相比不处理对照,经单宁酸处理后,豌豆蚜头部有7个GST基因上调表达,其中ApGST104、ApGSTX1上调表达3倍左右;胸部有10个GST基因上调表达,其中ApGSTD6上调表达6.4倍;腹部有10个GST基因上调表达,其中ApGST101、ApGST105上调5倍左右;中肠有9个GST基因上调表达,其中ApPGST105上调表达3.2倍。从结果可以看出,单宁酸对豌豆蚜GST基因的表达产生了影响,部分GST基因显著上调表达(P <0.05),表明GST基因可能在豌豆蚜对单宁酸的代谢中发挥重要的作用。

化感物质抑制连作黄瓜生长的作用机理

苯丙烯酸、对羟基苯甲酸为黄瓜根系分泌物中的主要化感物质组分。通过模拟根系分泌物中的化感物质进行土培和水培试验,证明苯丙烯酸、对羟基苯甲酸对连作黄瓜根系生长有明显的抑制作用。在50～250μmol/L浓度范围内,随处理浓度的加大,抑制根系对K+、NO3、H2PO4吸收的作用显著,养分外渗速率加快,组织外渗相对电导率逐渐提高。苯丙烯酸、对羟基苯甲酸强烈地抑制黄瓜根系脱氢酶、根系结合ATP酶、硝酸还原酶、超氧化物歧化酶的活性,随理浓度的增大抑制作用增强。

胜红蓟地上部化感作用物的分离与鉴定

胜红蓟（Ａｇｅｒａｔｕｍｃｏｎｙｚｏｉｄｅｓ）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。

不同化感水稻品种根系分泌物中萜类化合物的差异分析

以强化感水稻品种PI312 777和弱化感水稻品种Lemont为供试材料,运用“循环法”收集供试水稻经土壤和石英沙介质后的根系分泌物,并经乙醚萃取,所获萃取物经气相色谱 质谱联用仪(GC MS)测试,检索谱图库确定化合物.结果表明,乙醚萃取物中检测到含氧萜类化合物,如柠檬烯氧化物、柠檬烯二氧化物、香芹酮氧化物、香芹醇、雪松醇等,不同品种间含氧萜类化合物种类相似,但在不同介质中的存留方式和数量存在差异.文中还就不同培养方式和品种间萜类化合物的差异作了进一步讨论.

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 .

化感作用在杂草控制中的应用

杂草危害农作物的生长和发育,而大量施用除草剂会造成环境污染和增加杂草抗药性。利用植物相互间化感作用控制杂草非常有效,抑草植物通过释放化感物质并与杂草竞争生存环境,进而对杂草发芽和生长产生抑制作用。轮作、耕作等措施影响植物残茬化感物质的释放,造成抑草效果不同。化感育种是解决杂草危害的最有效途径,可使植物具有对杂草抑制作用的化感性状。