菌根和根分泌物在植物抗重金属中的作用

多年来人们对植物抗重金属的研究一直集中在植物体内的代谢调节和控制上。随着近年来对根际环境的研究,人们发现植物体外的根际环境对植物抗重金属有着重要的影响,目前研究主要集中在对菌根真菌和根系分泌物与植物抗重金属的关系,本文就近年来对菌根真菌和根系分泌物在植物抗重金属毒害中发挥的作用及其可能机理的研究状况作一概述,并对该领域的研究和应用前景作出展望。     

柏木根系分泌物对栾树细根形态及N、P含量的影响

为研究混交过程中柏木根系分泌物对栾树细根生长的影响,以一年生栾树盆栽幼苗为研究对象,通过施加1株、2株、4株、8株4个浓度柏木根系分泌物(分别记为G1、G2、G4、G8)于栾树盆栽中,探讨柏木根系分泌物对栾树幼苗1～5级细根形态及N、P含量的影响。结果表明:(1)栾树细根直径随根序的增加而增大,施加根系分泌物显著减小了1～2级细根的直径(P0.05);细根比根长、比表面积均随根序的增加而减小,施加根系分泌物显著增大了1～2级细根的比根长及比表面积(P0.05);随根系分泌物施加浓度的提高,栾树比根长及比表面积先增大,而直径先减小,然后均趋于平缓波动的态势。(2)栾树细根N、P含量均随根序的增加而减小,而N/P在根序间的变化不显著;施加柏木根系分泌物显著增大了栾树1～2级细根的N、P含量(P0.05),但减小了1～5级细根的N/P;随根系分泌物施加浓度的提高,栾树细根P含量增大,N/P减小,而N含量先增加后呈现平缓变化的趋势。(3)栾树细根N、P含量均与其比根长、比表面积和直径等形态特征之间呈显著的相关关系(P0.05)。研究发现,柏木根系分泌物可改善土壤养分的有效性,从而缓解栾树植株的缺P症状,细根通过调整其形态以提高养分利用效率;柏木根系分泌物主要影响栾树1～2级细根的形态及N、P含量;4株柏木根系分泌物的剂量更有利于栾树根系的生长。     

荞麦、高粱根系分泌物对玉米根边缘细胞和根生长的影响

植物的根系分泌物是植物根系与周围环境之间的化学媒介,通过传递特定的信息,调节根际微环境,影响周围植物的生长。玉米(Zea mays L.)和荞麦(Fagopyrum esculentum Moench)是农作物间套作体系中典型的不能搭配的组合,其障碍因素尚不清楚。以玉米为受体植物,采用根悬空培养的方法,研究了荞麦、高粱(Sorghum bicolor(L.) Moench)根系分泌物对玉米根边缘细胞和根生长的影响。结果发现,玉米根边缘细胞离体培养条件下,用荞麦根系分泌物中的小分子物质处理4、8 h显著诱导边缘细胞凋亡、死亡,细胞活率分别比对照降低了71.6%和72.3%;荞麦根系分泌物中的小分子物质对玉米根产生氧化胁迫,诱导根SOD、POD和CAT活性分别比对照高22.6%、33.9%和107.2%,根中超氧阴离子(O₂^-·)和脯氨酸含量分别比对照高33.9%和49.8%;荞麦根系分泌物中小分子物质的胁迫使根细胞膜透性增大,与对照相比升高80.0%,丙二醛(MDA)含量比对照升高31.5%;荞麦根系分泌物中小分子物质诱导根内源激素(IAA)含...     

Root exudates and their ecological consequences in forest ecosystems: Problems and perspective

植物根际过程与调控机理研究已成为当前土壤学最活跃、最敏感的研究领域, 而根系分泌物作为根系-土壤-微生物界面物质能量交换和信息传递的重要媒介物质, 是构成根际微生态系统活力与功能特征的内在驱动因素, 是根际概念与根际过程存在的重要前提和基础。然而, 由于传统的根际过程研究更强调以实际生产问题为导向, 加之农作物生长周期较短、操作便利等诸多因素, 以往对植物根系分泌物研究主要聚焦在农业生态系统, 而有关根系分泌物在森林生态系统中的重要作用与调控机理研究甚少, 认识相对零散和片段化。基于此, 该文结合作者实际研究工作中的主要成果和该领域国际前沿动态, 综述了森林根系分泌物的生态重要性, 重点论述了目前森林根系分泌物生态学研究中存在的主要问题与不足, 在此基础上展望了未来森林根系分泌物生态学研究中值得关注的重点方向和研究内容。     

森林根系分泌物生态学研究:问题与展望

植物根际过程与调控机理研究已成为当前土壤学最活跃、最敏感的研究领域,而根系分泌物作为根系-土壤-微生物界面物质能量交换和信息传递的重要媒介物质,是构成根际微生态系统活力与功能特征的内在驱动因素,是根际概念与根际过程存在的重要前提和基础。然而,由于传统的根际过程研究更强调以实际生产问题为导向,加之农作物生长周期较短、操作便利等诸多因素,以往对植物根系分泌物研究主要聚焦在农业生态系统,而有关根系分泌物在森林生态系统中的重要作用与调控机理研究甚少,认识相对零散和片段化。基于此,该文结合作者实际研究工作中的主要成果和该领域国际前沿动态,综述了森林根系分泌物的生态重要性,重点论述了目前森林根系分泌物生态学研究中存在的主要问题与不足,在此基础上展望了未来森林根系分泌物生态学研究中值得关注的重点方向和研究内容。     

植物根系分泌物主要生态功能研究进展

根系分泌物在植物根系-土壤-微生物互作过程及其生态反馈机制中发挥重要作用。在植物根际复杂网络互作过程中, 根系分泌物被认为是“根际对话”的媒介, 其在调控植物适应微生境、缓解根际养分竞争及构建根际微生物群落结构方面意义重大。该文结合国内外该领域主要研究成果, 综述了根系分泌物对植物生长、土壤微生物特性及土壤养分循环的影响, 并展望了未来根系分泌物的研究方向。     

Research Advances in the Main Ecological Functions of Root Exudates

根系分泌物在植物根系-土壤-微生物互作过程及其生态反馈机制中发挥重要作用。在植物根际复杂网络互作过程中, 根系分泌物被认为是“根际对话”的媒介, 其在调控植物适应微生境、缓解根际养分竞争及构建根际微生物群落结构方面意义重大。该文结合国内外该领域主要研究成果, 综述了根系分泌物对植物生长、土壤微生物特性及土壤养分循环的影响, 并展望了未来根系分泌物的研究方向。     

两种基因型大豆根分泌物对大豆根腐病菌的化感作用

采用生物模拟试验、化学分析等方法,研究了两种大豆基因型(9536、吉林30)的根分泌物中的糖、氨基酸、有机酸组分对大豆根腐病菌的化感作用.结果表明,两种大豆基因型(9536、吉林30)根分泌物糖组分表现出低浓度显著促进、高浓度显著抑制半裸镰孢菌、尖镰孢菌生长的规律,对粉红粘帚菌的生长影响不明显;氨基酸组分对上述三种病原菌所表现出的促进、抑制规律不同,9536基因型根分泌物氨基酸组分的中、高浓度处理对半裸镰孢菌、粉红粘帚菌、尖镰孢菌的生长表现出显著的抑制作用,而吉林30多表现出显著的促进作用;有机酸组分对半裸镰孢菌、粉红粘帚菌、尖镰孢菌生长都有显著的抑制作用.两种基因型大豆根分泌物(糖、氨基酸、有机酸组分)与根腐病害发生密切相关,大豆基因型不同,根分泌物对根腐病菌的化感促进或抑制作用有差异.     

根系分泌物介导下植物-土壤-微生物互作关系研究进展与展望

根系分泌物是植物与土壤进行物质交换和信息传递的重要载体物质, 是植物响应外界胁迫的重要途径, 是构成植物不同根际微生态特征的关键因素, 也是根际对话的主要调控者。根系分泌物对于生物地球化学循环、根际生态过程调控、植物生长发育等均具有重要功能, 尤其是在调控根际微生态系统结构与功能方面发挥着重要作用, 调节着植物-植物、植物-微生物、微生物-微生物间复杂的互作过程。植物化感作用、作物间套作、生物修复、生物入侵等都是现代农业生态学的研究热点, 它们都涉及十分复杂的根际生物学过程。越来越多的研究表明, 不论是同种植物还是不同种植物之间相互作用的正效应或是负效应, 都是由根系分泌物介导下的植物与特异微生物共同作用的结果。近年来, 随着现代生物技术的不断完善, 有关土壤这一“黑箱”的研究方法与技术取得了长足的进步, 尤其是各种宏组学技术(meta-omics technology), 如环境宏基因组学、宏转录组学、宏蛋白组学、宏代谢组学等的问世, 极大地推进了人们对土壤生物世界的认知, 尤其是对植物地下部生物多样性和功能多样性的深层次剖析, 根际生物学特性的研究成果被广泛运用于指导生产实践。深入系统地研究根系分泌物介导下的植物-土壤-微生物的相互作用方式与机理, 对揭示土壤微生态系统功能、定向调控植物根际生物学过程、促进农业生产可持续发展等具有重要的指导意义。该文综述了根系分泌物的概念、组成及功能, 论述了根系分泌物介导下植物与细菌、真菌、土壤动物群之间的密切关系, 总结了探索根际生物学特性的各种研究技术及其优缺点, 并对该领域未来的研究方向进行了展望。     

Advances and perspective in research on plant-soil-microbe interactions mediated by root exudates

根系分泌物是植物与土壤进行物质交换和信息传递的重要载体物质, 是植物响应外界胁迫的重要途径, 是构成植物不同根际微生态特征的关键因素, 也是根际对话的主要调控者。根系分泌物对于生物地球化学循环、根际生态过程调控、植物生长发育等均具有重要功能, 尤其是在调控根际微生态系统结构与功能方面发挥着重要作用, 调节着植物-植物、植物-微生物、微生物-微生物间复杂的互作过程。植物化感作用、作物间套作、生物修复、生物入侵等都是现代农业生态学的研究热点, 它们都涉及十分复杂的根际生物学过程。越来越多的研究表明, 不论是同种植物还是不同种植物之间相互作用的正效应或是负效应, 都是由根系分泌物介导下的植物与特异微生物共同作用的结果。近年来, 随着现代生物技术的不断完善, 有关土壤这一“黑箱”的研究方法与技术取得了长足的进步, 尤其是各种宏组学技术(meta-omics technology), 如环境宏基因组学、宏转录组学、宏蛋白组学、宏代谢组学等的问世, 极大地推进了人们对土壤生物世界的认知, 尤其是对植物地下部生物多样性和功能多样性的深层次剖析, 根际生物学特性的研究成果被广泛运用于指导生产实践。深入系统地研究根系分泌物介导下的植物-土壤-微生物的相互作用方式与机理, 对揭示土壤微生态系统功能、定向调控植物根际生物学过程、促进农业生产可持续发展等具有重要的指导意义。该文综述了根系分泌物的概念、组成及功能, 论述了根系分泌物介导下植物与细菌、真菌、土壤动物群之间的密切关系, 总结了探索根际生物学特性的各种研究技术及其优缺点, 并对该领域未来的研究方向进行了展望。     

植物根系分泌及其在林业中的意义

本文简要介绍了植物根系分泌物的成分、数量, 充分讨论了根系分泌的影响因素、根系分泌的部位及根系分泌物在土壤中扩散的范围, 并阐明了树木通过根系分泌对土壤营养条件、土壤微生物及其它相邻植物均有显著的影响。     

Regulation and function of root exudates

Root-secreted chemicals mediate multi-partite interactions in the rhizosphere, where plant roots continually respond to and alter their immediate environment. Increasing evidence suggests that root exudates initiate and modulate dialogue between roots and soil microbes. For example, root exudates serve as signals that initiate symbiosis with rhizobia and mycorrhizal fungi. In addition, root exudates maintain and support a highly specific diversity of microbes in the rhizosphere of a given particular plant species, thus suggesting a close evolutionary link. In this review, we focus mainly on compiling the information available on the regulation and mechanisms of root exudation processes, and provide some ideas related to the evolutionary role of root exudates in shaping soil microbial communities.     

根系分泌物生态学研究

在植物生长过程中 ,由根系的不同部位分泌或溢泌一些无机离子及有机化合物 ,这些物质统称为根系分泌物。植物在其生长过程中不断地分泌无机离子及有机化合物 ,这是植物长期适应外界环境而形成的一种适应机制。早在 2 0世纪 5 0年代就有人对植物根系分泌物进行了研究 ,Ｒｏｖｉｒａ等[4 3] 和Ｖａｎｃｕｒａ等[4 7] 对根土界面根系分泌物进行了系统的研究 ,切尔诺布里维卡[2 6 ] 研究了植物根系分泌物的生物学作用 ,揭示了其在间作中的作用 ,直到 70年代对根系分泌物的研究才出现了蓬勃发展的趋势。近年来的研究表明 ,根系分泌物是保持根际微…     

镉胁迫下小麦根系分泌物的变化

通过水培和砂培两种方法 ,研究了镉胁迫下小麦 ( Triticum aestivm L.)根系分泌物变化。通过研究镉对小麦根系分泌氨基酸和糖 ,根系分泌其它一些次生代谢物质等的影响 ,以及根系分泌物对蔬菜种子萌发的影响 ,探讨镉胁迫下植物根系的生理生态效应。研究结果表明 :镉胁迫下 ,小麦根系分泌物无论在量上还是质上都有变化。镉胁迫下根系分泌的电解质、糖类、氨基酸以及其它一些次生代谢物质都有所变化 ,但变化情况有差异。电解质外渗率、糖类随 Cd2 + 浓度升高而增加 ,在低浓度 Cd2 + 作用下 ( 0 .5 mg/ L) ,随处理浓度的升高 ,氨基酸分泌量增加 ;当处理浓度高于相应浓度时 ,氨基酸分泌量随浓度升高而减少。随 Cd2 + 浓度升高 ,次生代谢物分泌种类减少。这说明小麦通过改变根分泌作用而缓解镉危害。由于根系分泌次生代谢物的活动比较复杂 ,因而根系的分泌作用有待于进一步研究。根系分泌物中可能含有某些物质抑制萝卜、白菜种子萌发 ,这是涉及到植物他感作用的问题 ,值得并有待于进一步研究。初步分析小麦根系在不同的环境中对镉胁迫的响应方式 ,为以后根分泌物的深入研究提供了一定的思路 ,也为镉污染区农作物的合理栽培提供新的参考资料。     

根分泌物对根际矿物营养及根际微生物的效应

综述了根系分泌物对植物生长的生理生态学效应,并就根系分泌物的定义、产生机制、组成成分和影响因素等方面进行了讨论。指出根系分泌物在缓解低矿物营养胁迫对植株造成的伤害及决定根际微生物的种群密度和数量方面起着重要的作用;根系分泌物的产生机制多样,组成成分复杂,影响因素繁多。对根分泌物的深入研究有助于进一步了解植物体与土壤间进行的生理生化过程及其调控机制。     

Genetic control of root exudation

The literature on genetics of root exudation and on genotypic differences in qualitative and quantitative composition of root exudates in crop and native plant species was critically assessed. Differences in exudation have been reported for genotypes that differ in tolerance to nutrient deficiencies, ion toxicities, and pathogen attack. The exudation profile of a limited number of genotypes (frequently only two genotypes with the contrasting response to the environmental stress) have been reported to date. Little is known about the variability in larger samples of the germplasm or about actual genetics behind differential qualitative and quantitative composition of root exudates. Changing the exudation profile of a given genotype may be achieved by manipulating the biosynthetic capacity and by increasing the capacity of the plasma membrane to transport the specific compound out into the rhizosphere. Overexpression of the bacterial citrate synthase gene in the cytoplasm of tobacco plants resulted in exudation of large quantities of citrate into the rhizosphere and partial alleviation of the aluminium (Al) toxicity stress. A similar strategy of transforming plants with citrate synthase gene is being tried as a way of improving plant capacity to extract phosphorus (P) from soils with notoriously low P availability.More research into the genetic basis of qualitative and quantitative differences in root exudation is warranted. Understanding the genetic control of root exudation, followed by manipulation of qualitative and quantitative composition of root exudates, will result in better adaptation of plants to environmental conditions and a greater yield of crops.     

Root exudates of mycorrhizal tomato plants exhibit a different effect on microconidia germination of Fusarium oxysporum f. sp. lycopersici than root exudates from non-mycorrhizal tomato plants

The effect of root exudates from mycorrhizal and non-mycorrhizal tomato plants on microconidia germination of the tomato pathogen Fusarium oxysporum f. sp. lycopersici was tested. Microconidia germination was enhanced in the presence of root exudates from mycorrhizal tomato plants. The more tomato plants were colonized by the arbuscular mycorrhizal fungus Glomus mosseae, the more microconidia germination was increased, indicating that alterations of the exudation pattern depended on the degree of root AM colonization. Moreover, alterations of the exudation pattern of mycorrhizal plants are not only local, but also systemic. Testing the exudates from plants with a high and a low P level revealed that the alterations of the root exudates from mycorrhizal plants, resulting in a changed effect on microconidia germination, are not due to an improved P status of mycorrhizal plants.     

Probing short-term root exudation in Zea mays

Exudation of maize roots was studied using a microdrop recorder. The high-resolution measurements of relatively short-term changes in exudation seems to be one of the most useful and unproblematic applications of the microdrop recorder. When mannitol, polyethylene glycol (PEG) and kinetin were supplied to the medium bathing, the surfaces of excised maize roots, a marked decrease in root exudation was observed. The action of fusicoccin and that of abscisic acid (ABA) showed a sharp and then a slower decline on root exudation, though, enhanced exudation was sustained over a much longer period, in comparison to that recorded for mannitol and polyethylene glycol. A decline in the volume of exudates is related to an increase in the water deficit, in coincidence to changes in the osmotic gradient between root cells and the bathing medium generated by expelling exudates.     

Plant growth strategy determines the magnitude and direction of drought-induced changes in root exudates in subtropical forests

Root exudates are an important pathway for plant–microbial interactions and are highly sensitive to climate change. However, how extreme drought affects root exudates and the main components, as well as species-specific differences in response magnitude and direction, are poorly understood. In this study, root exudation rates of total carbon (C) and its components (e.g., sugar, organic acid, and amino acid) were measured under the control and extreme drought treatments (i.e., 70% throughfall reduction) by in situ collection of four tree species with different growth rates in a subtropical forest. We also quantified soil properties, root morphological traits, and mycorrhizal infection rates to examine the driving factors underlying variations in root exudation. Our results showed that extreme drought significantly decreased root exudation rates of total C, sugar, and amino acid by 17.8%, 30.8%, and 35.0%, respectively, but increased root exudation rate of organic acid by 38.6%, which were largely associated with drought-induced changes in tree growth rates, root morphological traits, and mycorrhizal infection rates. Specifically, trees with relatively high growth rates were more responsive to drought for root exudation rates compared with those with relatively low growth rates, which were closely related to root morphological traits and mycorrhizal infection rates. These findings highlight the importance of plant growth strategy in mediating drought-induced changes in root exudation rates. The coordinations among root exudation rates, root morphological traits, and mycorrhizal symbioses in response to drought could be incorporated into land surface models to improve the prediction of climate change impacts on rhizosphere C dynamics in forest ecosystems.     

Evaluating the role of root citrate exudation as a mechanism of aluminium resistance in maize genotypes

Organic anion exudation by roots as a mechanism of aluminium (Al) resistance has been intensively studied lately. In the present study, we evaluated qualitative and quantitative aspects of root exudation of organic anions in maize genotypes of distinct sensitivity to Al in response to Al exposure. Maize seedlings were grown axenically in nutrient solution and root exudates were collected along the whole seminal root axis for a short period (4 h) using a divided-root-chamber technique. In root exudates collected from 10-mm long root apices, citrate accounted for 67% of the total organic anions found, followed by malate (29%), trans-aconitate (3%), fumarate (<1%), and cis-aconitate (1%). Rates of citrate exudation from root apices of two genotypes with differential resistance to Al were consistently higher in the Al resistant one, differing by a factor of 1.7 – 3.0 across a range of external Al concentrations. Furthermore, relative Al resistance of eight maize genotypes correlated significantly well with their citrate exudation rate measured at 40 M Al. Higher exudation rates were accompanied by a less inhibited root elongation. The exudation of citrate along the longitudinal axis of fully developed seminal roots showed a particular pattern: citrate was exuded mainly in the regions of root apices, either belonging to the main root or to the lateral roots in the most basal part of the main root. The involvement of citrate in a mechanism of Al resistance is evaluated in terms of protection of the root from the effects of excess Al on root elongation and on nutrient uptake along a root axis showing distinct sites of citrate exudation.