湿地植物根表铁膜研究进展

湿地植物具有一系列生理和结构上适应浸水环境的特征,如根系的通气组织和渗氧能力,这使得植物根际微环境处于氧化状态,这样土壤中的铁和锰会在植物根表被氧化而形成红棕色的铁锰氧化物胶膜.土壤中的铁锰元素和局部的氧化环境是铁膜形成的2个重要条件.铁膜的主要组分为铁锰的氧化物及其水合物,它是一种两性胶体,可以通过离子之间的吸附-解吸、氧化-还原、有机-无机的络合等作用改变根际环境中重金属阳离子和养分的存在形态,从而影响这些离子的生物有效性,进而能影响土壤-湿地植被体系中污染物和养分的迁移.本文主要综述了湿地植物根系铁锰氧化物胶膜的形成、组成以及对植物吸收外部介质中的重金属和养分的影响,并提出了在今后的研究中仍值得进一步探讨和解决的问题.

Abstract：

Wetland plants have a series of physiological and anatomical characteristics to adapt flooding habitat, e.g. , their root aerenchyma and oxygen-penetrating capability can make the rhizospheric micro-environment be under oxidation condition, resulting in the formation of Fe/Mn plaques on root surface. Soil Fe and Mn and thee micro-environment oxidation condition are the two important prerequisites for the formation of the Fe/Mn plaques. The plaques are mainly com-posed of Fe-and Mn-0xides and their hydrates, which can alter the forms of heavy metals and nu-trients in rhizospberic micro-environment via the actions ahserption-desorption, oxidation-reduc-tion, and organic-inorganic chelation, etc. , and thereby, affect the bioavailability and the migra-tion of pollutants and nutrients in wetland soil-plant system. This paper reviewed the researches about the formation and composition of Fe/Mn plaques on wetland plant root surface, and the effects of the plaques on the heavy metals and nutrients uptake by wetland plants. Some problems worthy to be further approached were discussed.     

湿地植物根表的铁锰氧化物膜

湿地植物根系具有泌氧能力 ,使其根表及根际微环境呈氧化状态。因而 ,土壤溶液中一些还原性物质被氧化 ,如 Fe2 ,Mn2 ,形成的氧化物呈红色或红棕色胶膜状包裹在根表 ,称为铁锰氧化物膜。铁锰氧化物膜及其根际微环境是湿地植物根系吸收养分和污染物的门户 ,势必会影响这些物质的吸收。主要综述了铁锰氧化物膜的形成和组成 ,以及根表形成的氧化物膜的生态效应 ,也就是氧化物胶膜对植物根系吸收外部介质中的养分及污染物质——重金属离子的影响     

3种湿地植物对锌的吸收分配及其与根表铁氧化物胶膜的关系

在室内培养条件下,以灯心草、茭白和美人蕉3种湿地植物为材料,研究了湿地植物对锌的吸收分配能力与根表铁氧化物胶膜之间的关系.结果表明:(1)3种湿地植物积累锌的总量大小顺序为:茭白>美人蕉>灯心草,茭白积累锌的总量是灯心草的1.79倍;它们根表铁氧化物胶膜含量表现为灯心草>茭白>美人蕉,且其间存在显著差异(P<0.05).(2)锌在湿地植物中分配比例表现为;根中锌量>地上部分锌量>根表铁氧化物胶膜上吸附锌量;锌主要积累在湿地植物根中,地上部分和根表铁氧化物胶膜上吸附的锌量无显著差异.(3)湿地植物根表铁氧化物胶膜上吸附锌的数量与湿地植物地下部分锌含量呈极显著正相关(r=0.983 5**),增加根表铁氧化物胶膜上锌的数量就能明显提高地下部分锌含量;每千克土壤加入1 g FeSO4后,3种湿地植物积累锌的总量平均增加了21%.可见,湿地植物根表铁氧化物胶膜对锌的吸附也是湿地植物固定或积累锌的重要途径之一.     

根系活动对湿地植物根际铁异化还原的影响及机制研究进展

根系活动是影响湿地植物根际铁异化还原速率的关键因素之一。以往国内外湿地铁异化还原的研究多为分析和比较各类中宏观生境中铁异化还原能力的差异。近年来,湿地植物根际微域铁的生物地球化学行为也日益成为该领域的研究热点。综述了根际铁异化还原研究概况,梳理了根系活动对根际铁异化还原关键因子的作用机制,分析了根际铁异化还原和其他有机质代谢途径的竞争关系,探讨了根际铁异化还原对根系活动动态变化和异质性的响应,提出了根际铁异化还原的概念模型,并指出了未来我国湿地植物根际铁异化还原研究应加强的工作。     

典型湿地植物与湿地农田作物铁含量的季节变化特征

分析了三江平原自然湿地的优势种小叶章（Calamagrostis angustifolia）、乌拉苔草（Carex meyeriana）、毛苔草（C. lasiocarpa）和湿地农田中的大豆（Giycine max）和水稻（Oryza sativa）各器官铁含量的季节变化特征。结果表明：3种湿地植物各器官的铁含量呈金字塔构型,成熟期（9月）时位于金字塔尖的叶的铁含量约为位于塔底的下草根层（地下20～30 cm）的3.08％、4.42％和1.18％;幼龄期（5月）的铁含量垂直剖面Logistic拟合很好,R²分别达1.0000、0.9902和0.9954;整个生长季地下部分铁含量均逐渐降低,而地上部分具有种间和器官间差异。相比之下,农作物大豆和水稻的铁库主要集中在地下根系中,且随生长季的延长而逐渐富集;地上部分的铁含量远低于根系,其中地上部分又以叶的含铁量最高,随生长期的延长有所增加,平均增长率分别为5.67%和75.61％;成熟期作为种子的大豆和稻米铁含量最低,仅相当于同期根铁含量的5.50%和0.44%。不同物种间相同器官铁含量的差异随生长期不同而变化。湿地植物对土壤铁的富集能力要大于湿地农田作物。     

植物根表铁膜的形成及其营养与生态环境效应

论述了根表铁膜的形成条件、形态和矿物学组成及在根表的沉积位置,讨论了根表铁膜作为铁库改善植物Fe营养、影响P、Zn等营养状况的植物营养效应以及铁膜通过吸附或共沉淀的外在抗性机制和竞争代谢敏感位点的内在抗性机制,在提高植物抵抗Cu、Ni、Cd、As等重金属毒害和强酸、低碳的逆境环境等方面的生态环境效应．     

湿地中的植物入侵及湿地植物的入侵性

湿地享有“自然之肾”之称,但湿地生态系统正在受到严重的破坏,植物入侵已经成为干扰湿地生态系统的重要因素。同时湿地植物具有高度的入侵性,湿地和植物入侵都是现代生态学的研究热点。本文总结分析了湿地容易受到入侵的6种主要原因,包括湿地生境类型多样,分布广泛;湿地位置与植物扩散路线相关性;干扰;富营养化;湿地的脆弱性;外来种缺少天敌等。归纳了21种全球性主要湿地入侵植物种及其生态习性,并对湿地植物具有高度入侵性的共同特点以及解释湿地入侵现象的5种假说:天敌逃避说、宽耐受性假说、有效利用说、杂种优势说和异株克生说等作了综述分析。     

高等植物体内铁运输机制研究进展

铁是植物所必需的微量矿质元素,在光合作用、呼吸作用等过程中发挥着重要的作用。虽然铁在地壳中含量丰富,但生物有效获取率非常低。因此,探索高等植物铁吸收及运输机制一直是植物铁营养领域研究的热点问题。近几年来,人们对于高等植物体内铁运输,尤其是细胞内铁运输又有了新的认识。本文主要对高等植物体内长距离铁运输(木质部,韧皮部)和细胞内的铁运输(液泡,叶绿体和线粒体)两方面的运输机制进行了综述,这将帮助我们进一步了解植物铁代谢机制,对我们培育高铁含量作物和提高植物抗逆性有着重要意义。     

膜反应器培养植物细胞研究进展

本文就膜反应器在植物细胞培养中的研究现状进行了评述,并探讨了各类膜反应器存在的问题。     

关于湿地植物

技术图对生物圈的冲击明显表现于森林砍伐和草原开垦。湿地（weiland）则成为人类经济开发“沙海”中“漏网”的绿洲。然而,人口与人之物欲的恶性膨胀遂使这块多样物种的最后“伊甸园”受到威胁。基于上述,1971年子里海南岸的伊朗北部一个城市拉姆萨尔（Ramsar）缔结了《国际重要湿地,特别是水禽栖息地公约》。至1990年其缔约国已达61个。中国于1992年加入公约,并有6块湿地被载入帼际重要湿地名录》,其中便有江西的邵阳湖湿地。中国关于湿地的研究起步较晚,但步伐很快。在‘冲国湿地研究中心”的组织下人中国湿地》和有关各地湿地的…     

Red mud (RM)-Induced enhancement of iron plaque formation reduces arsenic and metal accumulation in two wetland plant species

Human activities have resulted in arsenic (As) and heavy metals accumulation in paddy soils in China. Phytoremediation has been suggested as an effective and low-cost method to clean up contaminated soils. A combined soil-sand pot experiment was conducted to investigate the influence of red mud (RM) supply on iron plaque formation and As and heavy metal accumulation in two wetland plant species (Cyperus alternifolius Rottb., Echinodorus amazonicus Rataj), using As and heavy metals polluted paddy soil combined with three rates of RM application (0, 2%, 5%). The results showed that RM supply significantly decreased As and heavy metals accumulation in shoots of the two plants due to the decrease of As and heavy metal availability and the enhancement of the formation of iron plaque on the root surface and in the rhizosphere. Both wetland plants supplied with RM tended to have more Fe plaque, higher As and heavy metals on roots and in their rhizospheres, and were more tolerant of As and heavy metal toxicity. The results suggest that RM-induced enhancement of the formation of iron plaque on the root surface and in the rhizosphere of wetland plants may be significant for remediation of soils contaminated with As and heavy metals.     

Root growth of wetland plants with different root types

A wastewater culture system was designed to study the root growth of eight species of wetland plants with two different root types. The system included a plastic barrel for holding the wastewater and a foam plate for holding the plant. The results indicated that the root growth of the plants with fibril roots was faster than that of the plants with rhizomatic roots. The species with fibril roots had higher root number (1349 per plant) than species with rhizomatic roots (549 per plant) after ten weeks of cultivation. The average root biomass of plants with fibril roots was 11.3 g per plant, whereas that of plants with rhizomatic roots was 7.4 g per plant. Fine root biomass of diameter ≤ 1 mm constituted 51.9% of the total root biomass in plants with fibril roots, whereas it accounted for only 25.1% in plants with rhizomatic roots. The root surface area of the plants with fibril roots (6933 cm² per plant) was markedly larger than that of the species with rhizomatic roots (1897 cm² per plant). The species with rhizomatic roots showed a longer root lifespan (46.6 days) than those with fibril roots (34.8 days).     

两种不同根系类型湿地植物的根系生长

实验设计了一个水培系统,利用生活污水培养,对4种“须根型”植物美人蕉、风车草、象草和香根草和4种根茎型植物菖蒲、水鬼蕉、芦苇和水烛的根系生长进行比较研究。该系统由用于盛污水的塑料桶（顶部直径36．5cm,底部直径30．Ocm,高34．5cm）和用于固定植物于水面的泡沫板构成。每桶种植1株植物,每种种5株。水培至10周时,须根型植物的平均根数达到1349条／株,而根茎型植物的平均根数只有549条／株。实验结束（水培第21周）时,须根型植物的平均根生物量为11．3g／株,根茎型植物的平均根生物量为7．4g／株。须根型植物根系中,d〈1mm的细根生物量占根系总生物量的51．9％,而根茎型植物d〈1mm的细根的生物量只占25．1％。根茎型植物的根生物量与地上生物量的比值为0．2,显著高于须根型湿地植物（0．1）。须根型湿地植物的根系表面积（6933cm^2／株）极显著地高于根茎型湿地植物（1897cm^2／株）。根茎型湿地植物根的平均寿命（46．6d）较须根型湿地植物根的平均寿命（34．8d）长。美人蕉的平均根数达1871条／株,根表面积达到22832cm^2／株,远较其他种高。     

Morphology, ecology, and contaminant removal efficiency of eight wetland plants with differing root systems

The objective of this study was to test the hypothesis that fibrous-root plants and rhizomatic-root plants are characterized by different root morphologies, root growth and distribution, and contaminant removal capabilities. Four fibrous-root and four rhizomatic-root wetland plants were studied in mono-cultured microcosms which received wastewater. Fibrous-root plants had significantly greater (P < 0.05) small-size root (diameter ≤ 1 mm) biomass and a larger (P < 0.05) root surface area per plant than the rhizomatic-root plants and exhibited accelerated growth in both shoots and roots compared to the rhizomatic-root plants. Fibrous-root plants developed the majority of their root biomass increment within a shallower gravel medium than the rhizomatic-root plants. All plants demonstrated fast root biomass growth from July to September. The wetland microcosms planted with fibrous-root plants showed significantly higher (P < 0.05) ammonium-nitrogen (NH₄-N) and nitrate-nitrogen (NO₃-N) removal rates from July to December than those planted with the rhizomatic-root plants. These results suggest that root characteristics of wetland plants, which are related to their shoot and root growth, root distribution, and decontamination ability, can be used in the selection of wetland plants with a higher contaminant removal capacity and in the construction of a multi-species wetland plant community. Handling editor: S. M. Thomaz     

Anatomical patterns of aerenchyma in aquatic and wetland plants

A well-developed aerenchyma is a major characteristic of aquatic plants. However, because such tissues are also found in wetland and terrestrial plants, it is not always possible to use their presence or absence to distinguish aquatic species. Whereas patterns of aerenchyma in roots have been studied in detail, those of the shoots have not. We collected and tested 110 species of various aquatic and wetland plants, including ferns (5), basal angiosperms (5), monocots (65), and eudicots (35). Three common and two rare types of aerenchyma were observed in their roots (three schizogeny and two lysigeny), plus five types of schizogeny in their shoots. We re-confirmed that, although a well-developed aerenchyma is more common in most organs of aquatic plants than in wetland plants, this presence cannot be used as strict evidence for the aquatic quality of vascular plants. Here, aerenchyma patterns were stable at the genus level, and the consistency of pattern was stronger in the roots than in the shoots. Furthermore, significant trends were verified in several higher taxa, and those consistencies of patterns partially coincided with their phylogeny.