作物根系形态与非生物胁迫耐性关系的研究进展

从水分、铝、磷等非生物胁迫方面综述了作物根系形态与非生物胁迫耐性之间的关系及主要研究进展,阐明了根系形态在作物逆境胁迫中的重要作用,对根系形态性状进行改良将是进一步提高作物产量潜力的重要方面之一。     

植物重金属镉(Cd2+)吸收、运输、积累及耐性机理研究进展

本文从植物对Cd2 吸收、运输及积累机制,以及Cd2 对植物的伤害、植物对Cd2 的耐性机制等三个层面对相关研究进展进行了综述,并对该研究领域的重点问题进行了展望。     

污染条件下VAM玉米元素积累和分布与根际重金属形态变化的关系

为了了解重金属Cu、Zn、Pb、Cd在土壤－根际－植物系统中的行为,揭示VAM植物减弱土壤中过量重金属对植物生理毒的抗性机理,采用原子吸收光谱测定Cu、Zn、Pb、Cd在污灌土壤中生长的VA菌根玉米和无菌根玉米中的积累和分布,并用连接形态分析技术分析了菌根际中Cu、Zn、Pb、Cd的形态分布和变化趋势,结果表明,Cu、Zn、Pb、Cd在菌根玉米中的积累量比非攻根中积累量分别减少10％、18％和29％,Cd积累量没有改变,生长7周后,菌根玉米是非菌根玉米生物量的1．5倍,与对照土壤相比,根际中除Cu交换态显著增加外,Zn、Pb、Cd各形态相对改变量显著大于非菌根,且菌根根际上中Cu、Zn、Pb有机结合态增加量显著大于非根际土,说明菌根际金属向稳定状态转移的程度显著大于非菌根际,同时,讨论了根际金属形态对金属有效性的影响,及其与菌根植物金属抗性机理的关系。     

香根草和鹅观草对Cu、Pb、Zn及其复合重金属的耐性研究

采用根伸长实验研究了香根草和鹅观草对重金属的耐性随着溶度的升高,耐性指数下降,当香根草和鹅观草受Cu2+、Pb2+、Zn2+单一污染时,三元素的危害作用依次为Cu2+>Pb2+>Zn2+;在Cu、Pb、Zn混合溶液中,其两种植物耐性指数的大小及变化与单一元素Cu溶液最为相似,Cu在溶液中起到主导因子作用;香根草与鹅观草相比,不论是受Cu、Pb、Zn单一污染还是三者的复合污染,香根草比鹅观草都具有较强抵制重金属的胁迫能力,其耐性指数大都大于0 5。因此香根草具有对重金属较强的耐性,在重金属污染土壤的植物修复及尾矿废弃地的植被重建中,可优先作为选择的材料。     

高等植物重金属耐性与超积累特性及其分子机理研究

由于重金属污染日益严重, 重金属在土壤_植物系统中的行为引起了人们的高度重视。高等植物对重金 属的耐性与积累性, 已经成为污染生态学研究的热点。近年来, 由于分子生态学等学科的发展, 有关植物对重金属的解毒和耐性机理、重金属离子富集机制的研究取得了较大进展。高等植物对重金属的耐性和积累在种间和基因型之间存在很大差异。根系是重金 属等土壤污染物进入植物的门户。根系分泌物改变重金属的生物有效性和毒性, 并在植物吸收重金属的过程中发挥重要作用。土壤中的大部分重金属离子都是通过金属转运蛋白进入根细胞, 并在植物体内进一步转运至液泡贮存。在重金属胁迫条件下植物螯合肽 (PC) 的合成是植物对胁迫的一种适应性反应。耐性基因型合成较多的PC, 谷胱甘肽 (GSH) 是合成PC的前体, 重金属与PC螯合并转移至液泡中贮存, 从而达到解毒效果。金属硫蛋白 (MTs) 与PC一样, 可以与重金属离子螯合, 从而降低重金属离子的毒性。该文从分子水平上论述了根系分泌物、金属转运蛋白、MTs、PC、GSH在重金属耐性及超积累性中的作用, 评述了近 10年来这方面的研究进展, 并在此基础上提出存在的问题和今后研究的重点。     

光强对木麻黄幼苗根系形态、解剖结构及其碳氮含量的影响

对光环境的灵敏响应使得森林中常见的光照异质性成为影响植物自我更新的关键因素,然而植物地下根系结构对光照的响应较为难测而缺乏深入研究。为探究不同光强下木麻黄根系响应策略,以一年生木麻黄(Casuarina equisetifolia)幼苗为试验材料,模拟森林幼苗生长的林外(CK)、林缘(L1)、林窗(L2)和林下光环境(L3)设置4种光照强度,测定及分析木麻黄幼苗的生长、根系形态、细根解剖结构及碳氮含量等指标。结果表明：(1)L1下,幼苗采取维持高度,降低横向生长的方式,保证正常累积生物量,随光照强度的下降,株高、地径、叶片生物量及地上部分生物量逐渐下降。(2)在根系表型上,幼苗随光限制的加重呈现抑制纵伸但促进根系的横向生长,其中总根长、根平均直径及根体积达到显著差异。在径级结构上,细根发育程度随光照减弱而下降;而适当的遮光(L1)促进粗根生长但L3时除根尖数较CK上升外,根长度、根表面积、根体积均显著下降。(3)1—3级细根解剖变化较大,相较CK,1级细根皮层细胞面积显著增加,但根半径、维管柱结构、表皮厚度等指标则显著下降,2级细根根半径、皮层细胞面积、表皮厚度明显减少,但维管柱结构仅在L2、L3时显著下降;3级细根根半径、皮层细胞面积和维管柱面积均较CK显著增大,L1时维管柱结构下降,但随光照减弱加重,维管柱面积和中柱占比均明显增加。(4)在碳氮含量上,CK与L1无显著差异,TC在L2时显著下降,TN则在L2时显著上升,TC、TN均在L3达到最大,而C:N随光强降低逐渐下降。综上所述,光限制时,木麻黄生物量及碳分配稳定根茎部分生长,采取“弱化吸收,强化储存”收缩型生长策略;当限制加重时,光合和呼吸作用失衡导致植物对细根投入养分的浪费,并最终造成林木死亡。研究结果为林下植被的更新提供理论参考。     

三种不同泌氧能力的红树植物对铅、锌、铜的耐性研究

红树林是分布于热带、亚热带潮间带的典型滨海生态系统。近年来,随着城市化和工业化的发展,滨海生态系统受重金属(例如铅、锌、铜等)的污染越来越严重,我国南方一些红树林底泥中的重金属浓度已达到甚或超过重度污染标准。由于沉积作用,红树林底泥被认为是一个能积累由潮水和河流淡水携带来的重金属的\"库\"。然而,红树植物具有很强的耐性生长于重度污染的底泥, 但其中的机理目前尚不清楚。由于长期被水淹没,红树林底泥是一个具氧化还原势低,还原性毒性物质(如Fe²⁺、Mn²⁺、H₂S、CH₄等)积累多,营养物质缺乏等特征的厌氧环境。为了适应这种生境,红树植物也进化出了一套与其他湿地植物类似的适应机制,植物能通过通气组织将地上部分的氧气输送到地下,一部分满足根的呼吸作用需要,一部分则通过根释放到根际,这被称为根的泌氧。根的泌氧可以氧化根际环境并且氧化还原性的毒性物质,以保证红树植物根免受毒害而延长生长。因此,根际泌氧是红树植物能适应生境的一个重要机理。本研究试图揭示红树植物在长期适应生境的过程中已经进化和发展出一系列形态解剖和生理生化特征是否在耐浸水的土壤条件,解除Fe²⁺、Mn²⁺等元素的毒性同时,是否也能解除其他重金属(铅、锌、铜)的毒性。通过对木榄、桐花和白骨壤三种不同泌氧能力的植物进行8周室内砂培试验发现:(1)三种植物的生长都被铅、锌、铜所抑制;(2)三种植物对铅、锌、铜都具有一定的耐性,然而,泌氧能力较弱的木榄比泌氧能力较强的桐花和白骨壤对铅、锌、铜的耐性高。     

水稻对重金属镉的吸收及耐性机理研究进展

Cd是一种不能降解、广泛存在于环境中的金属污染物,是植物体非必需元素、环境中生物毒性最强的重金属元素之一,主要来源于矿山开采、火力发电、机械加工,汽车尾气排放以及磷肥生产等。Cd可通过水稻根部进入机体,向地上部分迁移并蓄积,严重影响水稻正常生长, 并引起稻米Cd污染,通过食物链危害人类健康。从水稻Cd吸收影响因素及Cd在水稻中的吸收、运输和积累机理理等方面对水稻Cd污染研究现状进行综述,系统阐述了土壤pH、Eh、离子浓度等条件对水稻Cd吸收的影响,同时讨论了水稻对Cd胁迫的耐性机理及其分子机制。并指出存在的问题和研究方向。     

喀斯特山地煤矿废弃地几种优势植物的重金属耐性特征

对贵阳花溪区麦坪乡煤矿废弃地进行了野外调查, 对该地优势植物和土壤进行了采样, 测定样品As、Cd、Cu、Hg、Pb和Zn的含量, 发现当地优势植物雀稗(Paspalum thunbergii Kunth ex Steud.)地上部分Cu含量达到1058.12 mg•kg-1, 转移系数2.89, 富集系数16.07。研究了雀稗在铜离子胁迫实验中的根系活力变化和叶绿素浓度变化, 雀稗根系活力随实验进行而逐渐降低, 铜离子浓度为500 µg•mL-1的实验进行到第四周时TTC还原量达到最低值; 叶绿素浓度随着铜离子浓度的增加而缓慢降低, 进一步确认当地土著植物雀稗对铜离子有一定的耐受性。     

有机酸在植物对重金属耐性和解毒机制中的作用

植物对重金属的耐受和解毒机制可分为外部排斥和内部耐受两大类。该文综述了有机酸作为一类金属配位体, 在植物对重金属的这两大类机制中的重要作用。在重金属的外部排斥过程中, 植物根系分泌有机酸, 与金属离子形成稳定的金属配位体复合物, 改变重金属的移动性和生物可利用性, 阻止金属离子进入植物体内或避免其在根部敏感位点累积。此外, 有机酸还可与进入植物体内的金属离子螯合, 使其转化为无毒或毒性较小的结合形态, 缓解重金属的毒害效应, 实现植物对重金属的内部耐受。     

超富集植物对重金属耐受和富集机制的研究进展

超富集植物对重金属耐受和富集机制的研究成为近年来植物逆境生理研究的热点,在简要总结细胞壁沉淀、重金属螯合效应、酶活性机制和细胞区室化作用的基础上,概述了超富集植物对重金属的耐受机制,讨论了重金属跨根细胞质膜运输,共质体内运输、木质部运输和跨叶细胞膜运输的富集过程。     

Metal accumulation and tolerance in wetland plants

This paper briefly reviews the progress in studies of wetland plants in terms of heavy metal pollution. The current research mainly includes the following areas: (1) metal uptake, translocation, and distributions in wetland plants and toxicological effects on wetland plants, (2) radial oxygen loss (ROL) of wetland plants and its effects on metal mobility in rhizosphere soils, (3) constitutional metal tolerance in wetland plants, and (4) mechanisms of metal tolerance by wetland plants. Although a number of accomplishments have been achieved, many issues still remain unanswered. The future research effort is likely to focus on the ROL of wetland plants affecting metal speciation and bioavailability in rhizosphere soils, and the development of rhizosphere management technologies to facilitate and improve practical applications of phytoremediation of metalpolluted soils.     

Metal accumulation and tolerance in wetland plants

This paper briefly reviews the progress in studies of wetland plants in terms of heavy metal pollution. The current research mainly includes the following areas: (1) metal uptake, translocation, and distributions in wetland plants and toxicological effects on wetland plants, (2) radial oxygen loss (ROL) of wetland plants and its effects on metal mobility in rhizosphere soils, (3) constitutional metal tolerance in wetland plants, and (4) mechanisms of metal tolerance by wetland plants. Although a number of accomplishments have been achieved, many issues still remain unanswered. The future research effort is likely to focus on the ROL of wetland plants affecting metal speciation and bioavailability in rhizosphere soils, and the development of rhizosphere management technologies to facilitate and improve practical applications of phytoremediation of metal-polluted soils.     

Effects of morphological changes on metal accumulation in a salt marsh sediment of the Skallingen peninsula,Denmark

In 1931 a red-colored, sandy marker horizon was placed on the emergingSkallingen salt marsh. Sedimentation on top of the marker horizon sincethen shows two opposing tendencies. Coincident with salt marshdevelopment the sediments display up to 1964 a fining upward sequencewith an increasing content of organic matter. Since 1964 a nearby creekhas meandered towards the sampling plot. Consequently, the sedimentsbecome coarser with a decreasing organic matter content. Themorphological induced changes in sedimentary conditions strongly influencemetal content in the sediments and thereby hide anthropogenic inducedconcentration variations. Thus, an apparently diminishing Zn content (perkg dry weight) since 1964 could indicate lesser load to the area. However,corrected for grain size effects there is an increasing content of Zn. Othermetal concentrations (e.g. Cu) show a diminishing trend when corrected forgrain size effects and therefore indicate a reduced anthropogenic inducedload of these metals to the salt marsh.     

Cadmium and copper uptake and accumulation by Sesbania rostrata seedling, a N-fixing annual plant: implications for the mechanism of heavy metal tolerance

Sesbania rostrata,an annual tropical legume,has been found to be tolerant to heavy metals,with an unknown mechanism.It is a promising candidate species for revegetation at mine tailings.In this study,sequential extractions with five buffers and strong acids were used to extract various chemical forms of cadmium and copper in S.rostrata,with or without Cd or Cu treatments,so that the mechanisms of tolerance and detoxification could be inferred.Both metals had low transition rates from roots to the aboveground of S.rostrata.The transition ratio of Cd (4.00%) was higher than that of Cu (1.46%).The proportion of NaCl extracted Cd (mostly in proteinbinding forms) increased drastically in Cd treated plants from being undetectable in untreated plants.This suggests that Cd induced biochemical processes producing proteinlike phytochelatins that served as a major mechanism for the high Cd tolerance of S.rostrata.The case for Cu was quite different,indicating that the mechanism for metal tolerance in S.rostrata is metal-specific.The proportion of water-insoluble Cu (e.g.oxalate and phosphate) in roots increased significantly with Cu treatment,which partially explains the tolerance of S.rostrata to Cu.However,how S.rostrata copes with the high biotic activity of inorganic salts of Cu,which increased in all parts of the plant under Cu stress,is a question for future studies.Sesbania rostrata is among the very few N-fixing plants tolerant to heavy metals.This study provides evidence for the detoxification mechanism of metals in Sesbania rostrata.     

Cadmium and copper uptake and accumulation by Sesbania rostrata seedling, a N-fixing annual plant: implications for the mechanism of heavy metal tolerance

Sesbania rostrata, an annual tropical legume, has been found to be tolerant to heavy metals, with an unknown mechanism. It is a promising candidate species for revegetation at mine tailings. In this study, sequential extractions with five buffers and strong acids were used to extract various chemical forms of cadmium and copper in S. rostrata, with or without Cd or Cu treatments, so that the mechanisms of tolerance and detoxification could be inferred. Both metals had low transition rates from roots to the aboveground of S. rostrata. The transition ratio of Cd (4.00%) was higher than that of Cu (1.46%). The proportion of NaCl extracted Cd (mostly in protein-binding forms) increased drastically in Cd treated plants from being undetectable in untreated plants. This suggests that Cd induced biochemical processes producing protein-like phytochelatins that served as a major mechanism for the high Cd tolerance of S. rostrata. The case for Cu was quite different, indicating that the mechanism for metal tolerance in S. rostrata is metal-specific. The proportion of water-insoluble Cu (e.g. oxalate and phosphate) in roots increased significantly with Cu treatment, which partially explains the tolerance of S. rostrata to Cu. However, how S. rostrata copes with the high biotic activity of inorganic salts of Cu, which increased in all parts of the plant under Cu stress, is a question for future studies. Sesbania rostrata is among the very few N-fixing plants tolerant to heavy metals. This study provides evidence for the detoxification mechanism of metals in Sesbania rostrata.     

The role of the root cell wall in the heavy metal tolerance ofAthyrium yokoscense

Cells of the roots ofA. yokoscense growing on metalliferous habitats were fractionated into their cell wall and cytoplasmic components. About 70–90% of the total copper, zinc and cadmium was located in the cell wall. Copper had a markedly greater affinity for the cell wall than zinc and cadmium, and was prevented from entering the cytoplasm. A large proportion of these heavy metals in the cell wall were exchanged as ions. The capacity of the cell wall for exchanging metal ions inA. yokoscense was higher than in other plants growing on metalliferous habitats. However, compared with different ferns unable to grow on metalliferous habitats, this capacity was not unique toA. yokoscense. Consequetly, the root cell wall ofA. yokoscense is considered to be an important site of metal ion storage and may play the role of an excretory organ for heavy metals. On the other hand, as proportion of the heavy metls was transported to the cytoplasm, where the metal content was much higher than the average for normal ferns. This would suggest thatA. yokoscense has another metabolic mechanism related to metal tolerance.