植物对矿物的风化作用机制研究进展

矿物风化可为植物生长提供必需的营养矿物质,但也是毒性元素的主要来源之一.研究植物作用下的矿物风化过程,探索环境中元素的来源、分布和迁移转化规律,有助于深入认识植物和矿物的相互作用机制,为开展有益、有害元素的植物吸收与调控策略的研究提供科学依据.对国内外在植物与矿物风化研究领域的现状与进展进行分析和评述,发现:(1)根系分泌物的根际作用、植物对风化产物的吸收作用和植物共生菌根的辅助作用是植物驱动矿物风化的3种重要途径;(2)植物根系分泌物可通过H+酸解、有机酸络合、植物铁载体螯合和氧化还原等4种作用机制,协同促进矿物表面风化;(3)根际有机酸中羧基、羟基的结构特征及其与金属离子的配位关系是有机酸控制矿物风化的关键因素.认为从分子和时空四维尺度,探索土壤/矿物与根系界面中有机配体和金属的相互作用机制及元素的形态转化过程,是该领域的未来发展方向.(图4表1参86)     

滨海4种盐生植物根际土壤酶活性特征与主要养分的关系

植物可直接或间接地影响土壤酶的活性,根际土壤酶的种类和活性对土壤养分的速效化产生影响,从而影响植物的吸收利用。以滨海盐土和轻度盐化潮土为材料,利用根袋法研究滨海盐生植物对根际与非根际土壤养分含量以及酶活性的影响,为盐生植物在滨海盐渍土壤中的修复利用提供理论依据。结果表明：在两种土壤中,植物根际过氧化氢酶,脲酶和蛋白酶的活性表现出相反的变化,滨海盐土中,根际土3种酶的活性均高于非根际土;而轻度盐化潮土中的根际土3种酶活性均低于非根际土。在两种土壤中,根际土全氮质量分数比非根际土高,但全磷却比非根际土低。根际土速效态养分的变化则与全态养分的变化相反,4种植物的根际土速效氮质量分数均显著低于非根际土。除芦苇外,根际土速效磷质量分数均高于非根际土。滨海盐土中碱性磷酸酶、过氧化氢酶和转化酶和土壤中几种主要养分的相关性最紧密,较好地体现了4种滨海盐生植物根际的养分状况,也说明盐生植物对滨海盐土酶活性有较大的影响。对比4种植物根际土壤中的酶活性,在高盐质量分数的滨海盐土中,盐地碱蓬对根际土壤酶活性的影响最大     

植物根际微生态区域中铝的环境行为研究进展

铝毒是酸性土壤(pH<5.0)中影响植物生长的重要因素.根系环境中的铝离子可影响矿物营养的获取,增加植物对铝胁迫的风险.植物通过根系分泌有机酸、生物酶和其他物质来解除或减轻铝的毒害.从铝胁迫对根系分泌系统的影响、根际微环境中铝的毒理效应和根际微环境中铝的抗毒机制等3个方面对植物根际微生态区域中铝的环境行为研究进展进行了综述,并对今后该领域的研究方向进行了展望.     

干旱胁迫对植物根际环境影响的研究进展

全球气候变化下频发的干旱灾害已成为一个世界范围内的重大气候问题.根际环境是植物适应极端环境的有效方式之一,探讨干旱胁迫下根际环境改变及其与植物抗逆性和生产力的关系,已逐渐成为包括植物营养学、植物生理学、土壤学、微生物学等多学科的研究热点.本文在介绍干旱的严重性及根际环境的重要性的基础上,根据近年来国内外关于干旱对植物根际环境影响的研究成果,重点阐述干旱胁迫对植物根系分泌物的组成和含量、根际土壤碳氮磷养分状况、根际土壤酶活性及根际微生物数量和种群结构的影响,结果表明干旱胁迫不仅会提高植物根系分泌物的数量,改变其组成,而且会改变根际土壤酶活性及土壤微生物群落结构多样性与功能,同时也会改变土壤养分的循环与可利用性,从而影响植物生长,且这些改变会因植物种类、植物所处发育阶段、干旱胁迫强度与时间等的不同而异;但这些研究仅从现象上对其变化趋势进行了探究,目前对其相关机理性的研究仍非常缺乏、不够系统深入.未来应结合一些现代的新技术和方法,从根际化学信号及微生物组学的细微尺度上,加强干旱胁迫及其与其他环境胁迫耦合下植物根际环境变化与机理的系统深入研究,对丰富和推进植物对干旱逆境的适应与响应机理性的认识具有重要意义.(参91)     

几种固沙植物根际土壤微生物特性研究

研究了红柳、梭梭、沙拐3种固沙植物的根际和根外土壤微生物数量、组成、生理群微生物及土壤养分。结果表明：这3种固沙植物具有较强的根际正效应，其R/S在1.69-75.24之间，以梭梭的根际效应最大，沙拐枣其次，红柳最小，固沙植物的种植显著增加了微生物数量，促进有机质的积累和植物有效养分的转化，有利于流沙的成土发育。表7参9     

南亚热带不同植被根际微生物数量与根际土壤养分状况

研究了包括尾叶桉、广东凤丫蕨、柳叶竹、大叶相思、青皮、木荷、湿地松在内的7种南亚热带不同植物植被下土壤根际微生物与根际养分状况及其相关关系。结果表明,根际环境对细菌有明显的正效应,对放线菌和真菌有正、负两方面的影响,但对根际微生物总量具有根际效应明显;在南亚热带森林生态系统中.在植物的某些生长季节,微生物的根际效应与土壤养分的根际效应一致     

凤庆县不同古茶园根际与非根际土壤酶活性及其化学计量特征

研究不同古茶园土壤养分状况间的差异影响,可为古茶园的土壤养分管理提供理论依据,实现茶园的提质增效.以凤庆县郭大寨乡3个典型古茶园的根际与非根际土壤为研究对象,探究其根际与非根际土壤理化性质、土壤酶活性及其化学计量比之间的关系.结果显示：（1）茶园根际与非根际土壤养分含量及酶活性差异显著（P <0.05）,且表现出不同的土壤营养条件.（2）不同茶园的根际土壤含水量、全碳、全氮、全磷含量差异显著（P <0.05）,均表现为大箐>龙潭>琼英;同时,龙潭茶园土壤pH=4.5为茶树生长最适值.（3）不同茶园非根际土壤胞外酶活性的高低表现为大箐>龙潭>琼英,其活性与土壤含水量、全碳、全氮、全磷含量正相关,其中土壤含水量解释了97.2%变异,与pH值负相关.而在植物根系的作用下,根际土壤酶活性呈现出不同变化趋势;其活性与土壤含水量、pH值、全碳、全氮、全磷含量均正相关,土壤含水量解释了93.9%的变异,全碳解释了5.2%的变异.（4）根据土壤酶化学计量比矢量分析,3个茶园土壤微生物受碳源限制程度不同,限制程度为琼英>龙潭>大箐,大箐茶园土壤微生物受到一...     

2种入侵植物对根际土壤微生物种群及代谢的影响

选取2种入侵植物（一年蓬Annual Fleabane及加拿大蓬Erigeron Canadensis）及本土植物（艾蒿Artemisia argyi）的根际土壤微生物种群为研究对象,以分析不同根际土壤微生物种群的数量及测定根际土壤微生物酶活的活性为切入点来探析入侵植物对土壤微生物的影响及其响应机制。结果显示：2种入侵植物显著增加了其根际土壤中的细菌的数量,而显著抑制了真菌与放线菌的数量。另外,入侵植物一年蓬显著抑制其根际土壤中纤维素酶的活性,而3种植物的根际土壤硝酸还原酶活性无显著差异。入侵植物对其他3种土壤酶（即转化酶、脲酶及酸性磷酸酶）活性的影响却呈现出截然相反的影响,即一年蓬显著增加了3种根际土壤酶的活性,而加拿大蓬却显著减少了3种根际土壤酶的活性。导致这种现象的原因可能是不同入侵植物的根系释放不同的化学物质进而对土壤微生物的数量和活性造成不同的影响。     

根际养分活化与吸收过程的定量模拟研究进展

在论述植物根系作为养分的主动吸收槽．对根际养分生物有效性产生重要作用的前提下，本文扼要讨论了根际pH值变化、根分泌螯合物与还原性物及根际微生物在根际土壤养分活化中的作用过程，并重点评述了有关养分活化与吸收模拟模型的研究进展与发展趋势．     

根系分泌物及其在植物营养中的作用

论述了根系分泌物的种类和影响因素，根系分泌物在植物营养中的调节作用、异种克生作用，根系分泌物与根际微生物的相互作用。在铁胁迫条件下，许多高等植物都能产生一系列生理和形态方面的适应性反应，禾本科植物通过根际特定分泌物——麦根酸类物质来自动调节其体内的铁营养状况；在磷胁迫条件下，根系分泌的低分子有机酸种类主要有柠檬酸、草酸、酒石酸和苹果酸，它们在植物根际的富集能明显促进土壤中磷的释放，提高作物对磷的吸收，缓解植物的磷胁迫；在锌胁迫条件下，双子叶植物的根系分泌物对锌的活化作用不明显，而禾本科植物的根系分泌物可以活化石灰性土壤中难溶性锌。     

不同退化程度喀斯特生态系统根际土壤的养分分布特征

以贵州中部喀斯特地区由乔木林、灌木林和灌草丛等不同退化程度生态系统中的优势物种根际土壤为研究对象,测定其C、N、P全量及有效态质量分数,分析各优势物种根际土壤的养分变化。结果表明：3个生态系统中不同优势物种根际各类土壤养分质量分数变化较大,其中,土壤C、N、P养分为乔木林中园果化香根际土壤质量分数最高,白枥根际养分质量分数最低。可溶性有机碳质量分数为乔木林中最低,其平均水平不超过10 mg·kg-1。土壤磷素的供给能力为乔木林的园果化香和刺秋相对较强,其中园果化香中达到1.5%。而且优势树种间根际土壤有效态养分质量分数的差异明显高于全量养分,说明喀斯特地区根际土壤养分差异性主要受植被因素的影响,土壤有效态养分较全量养分对植被群落演替的响应更为灵敏,而且根际土壤养分质量分数和形态的变化与土壤有机碳质量分数有显著的正相关关系,这进一步说明喀斯特地区植被类型的变化对土壤养分的循环利用具有重要的影响作用。     

Influence of Dissolved Organic Matter On the Bio-Availability and Toxicity of Metals in Soils and Aquatic Systems

Cations in soil are essential for the growth of plants and micro-organisms. Their availability is dependent on soil organic matter. Soil organic matter (SOM) is heterogeneous comprising amino, aliphatic and phenolic acids, but particularly humic substances. All these substances can complex cations selectively. Mechanisms of complexation with dissolved organic matter are discussed. Such complexation can lead to the apparently contradictory observations that dissolved organic matter (DOM) can either increase the concentration of some less soluble nutrients, making them more available for plant uptake, or make them less available and hence less toxic. the importance of DOM is discussed in relation to soil solution, particularly the rhizosphere, and also in relation to aquatic systems. the latter systems contain mainly dissolved humic substances whereas in the soil, non-humic substances assume a greater importance.

SOM in the rhizosphere is derived from plant, microbial and animal remains but much, especially the water-soluble compounds, are acquired through root exudation. Exudation has important consequences for enhanced nutrient availability as a result of the production of non-humic substances such as amino, aliphatic and phenolic acids. in future, the role of root exudation in relation to DOM and nutrient availability should be investigated more fully, particularly as predicted elevated CO₂ levels are likely to have a major impact on root exudation, nutrient availability, and possibly ecosystem community structure and functioning. It is likely that more information will become available on aquatic systems as more highly sensitive techniques and equipment capable of dealing with low concentrations of DOM in these systems become available.     

Influence of Dissolved Organic Matter On the Bio-Availability and Toxicity of Metals in Soils and Aquatic Systems

Cations in soil are essential for the growth of plants and micro-organisms. Their availability is dependent on soil organic matter. Soil organic matter (SOM) is heterogeneous comprising amino, aliphatic and phenolic acids, but particularly humic substances. All these substances can complex cations selectively. Mechanisms of complexation with dissolved organic matter are discussed. Such complexation can lead to the apparently contradictory observations that dissolved organic matter (DOM) can either increase the concentration of some less soluble nutrients, making them more available for plant uptake, or make them less available and hence less toxic. the importance of DOM is discussed in relation to soil solution, particularly the rhizosphere, and also in relation to aquatic systems. the latter systems contain mainly dissolved humic substances whereas in the soil, non-humic substances assume a greater importance.

SOM in the rhizosphere is derived from plant, microbial and animal remains but much, especially the water-soluble compounds, are acquired through root exudation. Exudation has important consequences for enhanced nutrient availability as a result of the production of non-humic substances such as amino, aliphatic and phenolic acids. in future, the role of root exudation in relation to DOM and nutrient availability should be investigated more fully, particularly as predicted elevated CO₂ levels are likely to have a major impact on root exudation, nutrient availability, and possibly ecosystem community structure and functioning. It is likely that more information will become available on aquatic systems as more highly sensitive techniques and equipment capable of dealing with low concentrations of DOM in these systems become available.     

VA菌根对喀斯特草本群落植物根际养分影响研究

以贵州花江喀斯特高原生态综合治理试验示范区内草本群落阶段的几种主要植物为材料,对其根际微生态环境进行了研究,包括根际土壤化学性质、土壤酶活性和VA菌根侵染率及AMF孢子密度。结果表明：VA菌根侵染率和根际土壤中AMF孢子密度存在极显著正相关,相关系数达到0.97;不同植物根际土壤的化学指标和土壤酶活性均表现出较强的根际效应,即R/S〉1;VA菌根侵染率与pH值存在显著负相关,与有效磷质量分数存在极显著正相关,与碱性磷酸酶存在显著正相关,说明VA菌根能够促进土壤中难溶态磷往有效磷方向转化;AMF对宿主植物的侵染能够在一定程度上改善根际微生态环境的营养状况。     

蕉园土壤因子与香蕉枯萎病发病的相关性研究

香蕉枯萎病（Fusarium oysporum f.cubense）是当前严重威胁我国华南地区香蕉生产的重要土传病害,目前尚未找到有效的防治方法。于2010年采集了3个典型香蕉枯萎病患病样地（尖峰、冲坡、十月田）和2个健康样地（临高、广州）的根际与非根际土壤样品共46份,采用常规分析方法测定了19项土壤理化指标含量。旨在从农艺措施的角度考虑香蕉枯萎病的防治提供理论依据。结果表明：健康蕉园的大多理化性状和养分含量高于患病蕉园。尤以土壤粘粒、有机质、CEC、全N、全P、有效P、有效Cu、有效Fe、有效B和交换性Ca含量表现更为明显,其在健康蕉园中的含量均为患病蕉园的1.5倍以上。同一患病蕉园根际土壤中的pH值随植株感病级别增加而上升,而有效P和有效B含量随植株感病级别增加而降低。由此可以推论,在蕉园适当增施P肥和B肥有助于抑制香蕉枯萎病发生。     

Tree species and mycorrhizal associations influence the magnitude of rhizosphere effects

Previous research on the effects of tree species on soil processes has focused primarily on the role of leaf litter inputs. We quantified the extent to which arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) tree species influence soil microbial activity and nutrient availability through rhizosphere effects. Rhizosphere soil, bulk soil, and fine roots were collected from 12 monospecifc plots (six AM and six ECM tree species) planted on a common soil at the Turkey Hill Plantations in Dryden, New York. Rhizosphere effects were estimated by the percentage difference between rhizosphere and bulk soil samples for several assays. Rhizosphere effects on soil microbes and their activities were significant for ECM species but in only a few cases for AM species. In AM tree species, microbial biomass, net N mineralization, and phosphatase enzyme activity in the rhizosphere were 10-12% greater than in bulk soil. In ECM tree species, rhizosphere effects for microbial biomass, C mineralization rates, net N mineralization, and phosphatase activity were 25-30% greater than bulk soil, and significantly greater than AM rhizosphere effects. The magnitude of rhizosphere effects was negatively correlated with the degree of mycorrhizal colonization in AM tree species (r = -0.83) and with fine root biomass (r = -0.88) in ECM tree species, suggesting that different factors influence rhizosphere effects in tree species forming different mycorrhizal associations. Rhizosphere effects on net N mineralization and phosphatase activity were also much greater in soils with pH < 4.3 for both AM and ECM tree species, suggesting that soil pH and its relation to nutrient availability may also influence the magnitude of rhizosphere effects. Our results support the idea that tree roots stimulate nutrient availability in the rhizosphere, and that systematic differences between AM and ECM may result in distinctive rhizosphere effects for C, N, and P cycling between AM and ECM tree species.