菲和芘对土壤中植物根伸长抑制的生态毒性效应

测定了草甸棕壤条件下 ,菲、芘对小麦、白菜、西红柿 3种植物根伸长抑制率 ,以及复合污染毒性效应。结果表明 ,菲、芘浓度与植物根伸长抑制率呈显著线性或对数相关 (P =0 0 5 )。 2种有机物对植物根伸长抑制强度为菲 >芘。这与菲、芘的水中溶解度明显相关。与土壤脱氢酶活性和蚕豆根尖微核实验结果相比 ,植物根伸长对菲、芘毒性更敏感。小麦为有机污染的最敏感指示植物。菲、芘复合污染产生明显协同作用。     

重金属对土壤中小麦种子发芽与根伸长抑制的生态毒性

测定了4种土壤（红壤、草甸棕壤、暗棕壤和栗钙土）条件下,Cu,Zn,Pb和Cd单一污染对小麦种子发芽与根伸长抑制主及其复合污染效应（暗棕壤条件下）。结果表明,同一浓度下,重金属对小麦根伸长抑制率均明显大于对种子发芽抑制率,植物根对金属污染的生态毒性比种子发芽敏感,土壤有机质和土壤N含量与Cu,Zn,Pb和Cd污染对小麦根伸长抑制率显著负相关（R^2OR=0.91,R^2K-N=0.92),土壤PH和阳离子交换量与Cu,Zn,Pb和Cd污染对小麦根伸长抑制率的相关性不显著（R^2PH=0.62,R^2CEC=0.60),在单一污染对小麦根伸长为刺激作用浓度（较低浓度）或为抑制作用浓度下（较高浓度）,复合污染均表现为协同作用。^     

重金属对土壤中萝卜种子发芽与根伸长抑制的生态毒性

高等植物是生态系统中的基本组成部分。一个平衡、稳定的生态系统生产健康、优良的高等植物。反之 ,一个不稳定或受到外来污染的生态系统 ,对高等植物的生长可带来不利和可见的负面影响。因此 ,利用高等植物的生长状况监测土壤污染程度 ,是从生态学角度衡量土壤健康状况 ,评价土壤质量的重要方法之一[4 ,6] 1) 。土壤生态毒理学评价方法是对化学分析方法的重要补充。目前已建立的高等植物毒理试验有三种方法 ,即 1根伸长试验 ;2种子发芽试验 ;3早期植物幼苗生长试验[3 ,5,6,10 ] 。最初 ,这类试验主要用于纯化学品的毒性检验 ,但随着对土壤…     

污染物在根-土界面的化学行为与生态效应

根-土界面是污染物进入植物体内的主要通道和导致一系列生态安全问题的特殊微生态区,本文提出污染物在根-土界面上的化学行为和生态效应包括根际化学行为与生态效应,根系化学行为与生态效应两个方面的具体内容,并从理论上根据最新的研究进展对这两方面内容进行了探讨,指出根际化学行为与生态效应包括根际pH环境与吸附行为、根际氧化-还原行为、根际化学致毒效应、根际微生物效应及根际生物酶反应等;根系化学行为与生态效应包括根系分泌物、根系酶系统的影响、干扰正常生理过程、改变细胞结构与功能、干扰生物大分子的结构和功能等,并阐述根-土界面上的化学行为和生态效应在污染生态学中的重要性以及研究中存在的问题。     

土壤外源金霉素污染对蚯蚓生长发育的生态毒性效应

采用赤子爱胜蚓作为受试生物,研究了土壤金霉素污染对蚯蚓生长发育的慢性毒性效应.结果表明： 暴露7 d时,1、10、100 mg·kg^-1金霉素对蚯蚓体质量均无显著影响,暴露21 d后,10、100 mg·kg^-1金霉素对蚯蚓体质量产生显著抑制作用;1、10、100 mg·kg^-1金霉素均诱导了蚯蚓体内可溶性蛋白含量的增加,且暴露浓度越高,诱导效应越强;1、10、100 mg·kg^-1金霉素胁迫下蚯蚓体内的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)均有不同程度的上升;暴露28 d后,蚯蚓的基因表达也产生了明显变化. 表明金霉素污染对蚯蚓的生长发育具有慢性生态毒性效应,蚯蚓体质量、可溶性蛋白、抗氧化防御酶和基因表达等指标可以作为评价金霉素毒性的生物标志物.     

1,2,4-三氯苯胁迫对萌发大豆种子中活性氧的影响

以盆栽法研究了不同浓度 1,2 ,4 三氯苯 (TCB)胁迫对萌发大豆种子中活性氧代谢的影响 .结果表明 ,10 0～ 30 0 μg·g-1TCB胁迫初期 (1～ 3天 )促使萌发大豆种子呼吸强度升高及其峰值提前出现 ,超氧阴离子自由基 (O2 - )及过氧化氢 (H2 O2 )的积累显著增加 ,同时伴随丙二醛 (MDA)含量升高 ,显示发生膜脂质过氧化作用 .TCB胁迫 1～ 6天使活性氧清除酶功能紊乱 ,其中过氧化物酶 (POD)活性升高 ,超氧化物岐化酶 (SOD)活性开始上升后转为下降 .在萌发大豆种子受TCB胁迫伤害过程中 ,活性氧代谢失衡造成的膜脂质过氧化将起着重要作用 .     

Effects of Soil Structure on Pea (Pisum sativum L.) Root Development According to Sowing Date and Cultivar

Spring peas are known to be very sensitive to compaction, particularly when sowing takes place soon after winter. Winter peas, which are sown in autumn, should present an opportunity to sow the crop in better soil structural conditions than for spring peas, because of more favourable moisture conditions at that time. As environmental conditions have a big influence on root systems, it is important to determine the effects of soil structure on pea root systems for different cultivars and sowing dates. A spring pea cultivar and a winter pea cultivar were both sown at two dates (one in autumn and one in spring) on soils with different plough-layer structures (compacted and uncompacted) at two sites in 2002 and one site in 2003. Soil structure was characterised by bulk density and the percentage of highly compacted zones in the ploughed layer. Root distribution maps were produced every month, from February to maturity. Root development was described in terms of general root dynamics, root elongation rate (RER) in the subsoil, final maximum root depth (Dmax) and root distribution at maturity. Root depth dynamics depended on compaction and its interaction with climatic conditions. The effects of compaction on RER in the subsoil depended on the experimental conditions. Dmax was reduced by 0.10 m by compaction. Compaction also reduced root distribution between 10 and 40% in the ploughed layer only. Pea cultivars differed in sensitivity to soil compaction, with a direct effect on the final depth explored by roots. These results are discussed in terms of their relevance to water and nutrient uptake.     

Root Growth-promoting Activity of Unsaturated Oligomeric Uronates from Alginate on Carrot and Rice Plants

The root elongation activity of unsaturated oligomeric uronates from alginate on carrot and rice plants was investigated. Unsaturated oligomeric uronates were prepared by digesting polymannuronate (PM) and polyguluronate (PG) with an alginate lyase purified from Pseudoalteromonas sp. strain No. 272. The root elongation activity was measured by elongation in length of carrot- and rice-excised root incubated in the B5-medium containing 0.8% agar in the dark. PM and PG showed no activity, but the enzymatic digestion mixtures of PG had promoting activity on roots of both plants at a final concentration of 0.5 mg/ml. The maximum activity was obtained at 0.75 mg/ml. The dependence of activity on degree of polymerization of the uronates was tested and the pentamer was most active, but the mechanism of the action of unsaturated uronates on the cells remains to be solved.     

结合态氮对根瘤菌生长液诱导的苜蓿根毛变形的抑制

以苜蓿根瘤菌和其宿主苜蓿为材料,由结合态氮影响苜蓿根瘤菌生长液诱导宿主根毛变形的功能发现,硝态氮和铵态氮均能有效地抑制根瘤菌生长液诱导的宿主根毛变形。而其抑制作用随结合态氮浓度的增加、作用时间的延长而增强。该抑制作用发生在结合态氮浓度和作用时间分别达到1mmol/L和12h时,或当其浓度和作用时间分别为6mmol/L和48h时,根瘤菌生长液引起根毛变形的植株百分率下降到10％。硝态氮与铵态氮抑制根瘤菌生长液诱导根毛变形的作用相类似。     

生长素类化合物及6－苯甲基腺嘌呤对拟南芥主根生长的抑制效应比较

为更好的研究生长素类化合物及6-苯甲基腺嘌呤（6－BA）对细胞分裂和细胞伸长的影响,以拟南芥主根为材料,从组织学水平比较了IAA、NAA、2,4－D和6－BA对拟南芥主根分生区和伸长区的抑制效应,发现IAA和NAA效果是相似的,可以通过促进细胞分裂显著增加根分生区长度,但也显著缩短主根仲长区长度,而2,4－D和6－BA则通过抑制细胞分裂来显著缩短根分生区长度,同时也显著缩短根伸长区的长度。     

Comparison of Designed Channel Restoration and Riparian Buffer Restoration Effects on Riparian Soils

Stream restoration is often employed in efforts to stabilize eroding channel banks. Banks are stabilized through a designed channel approach, which involves grading and armoring of stream banks using heavy machinery, or alternatively through planting of seedlings and saplings to establish forested riparian buffers. We hypothesized that designed channel restoration would have detrimental impacts on riparian soils but that soils would recover over time, and we hypothesized that riparian buffer restoration would not impact riparian soils. We tested these hypotheses by comparing soil attributes (bulk density, soil organic matter, and root biomass) at reaches that had undergone designed channel and riparian buffer restoration in different years (project ages ranged from 2 to 16 years) to paired urban (unrestored) control reaches. Soil properties in sub‐surface soil layers (10–20 and 20–30 cm depth) at both recent (<10 years old) and older (>10 years old) designed channel reaches differed significantly from paired urban control soils; bulk density was higher and root biomass lower in manipulated reaches compared to urban control reaches. At many designed channel reaches, bulk density exceeded values known to restrict root growth. These results indicate that compaction and disturbance of riparian soils may be a significant unintended consequence of designed channel restoration and can persist for at least a decade. In contrast, we found no significant differences in soil properties between riparian buffer restoration reaches and urban control reaches. Thus, the results indicate that riparian buffer restoration is a more ecologically favorable method than designed channel restoration for bank stabilization.     

Root Growth Effects on Soluble C and P in Manured and Non-manured Soils

There is limited research on relationships between root characteristics and soil chemical properties and processes. Because previous studies have shown specific C compounds may release previously sorbed P and make P more plant-available, crops which contribute to high soil C levels could play an important role in soil P cycling. The objectives of this study were to determine (1) whether rotation crops had different amounts of root growth, (2) whether different amounts of root growth among the crop species could be related to different levels of soluble soil C and (3) whether there were differences in P concentration among the soils under different crops that could be related to soluble C soil concentration. Roots and soil from potato (Solanum tuberosum L.), barley (Hordeum vulgare L.), soybean (Glycine max (L.) Merr.), and a forage consisting of alfalfa (Medicago sativa L.) and timothy (Phleum pretense L.) were sampled from the Aroostook Research Farm in Presque Isle, Maine, during the summers of 2003 and 2004 to determine root length density (RLD) and soluble C and P concentrations. Half of the sampled plots were amended with beef manure and half were not amended. Barley and forage consistently had higher RLD than potato or soybean crops. Barley and forage typically had higher concentrations of soluble soil C than potato or soybean, but the differences were significant at only three of the five sampling dates. RLD was significantly correlated to soluble C (r=0.56) only for amended soils on the August 2003 sampling date. For other dates r values were non-significant and ranged from 0.32 to 0.49. As with soil C, soluble soil P levels were typically higher in barley and forage than in potato or soybean crops. Significant differences were detected at four of the five sampling dates. Correlations between soluble C and soluble P were significant at two of the five sampling dates (r = 0.58 and 0.62) in amended soils and one of five sampling dates (r = 0.80) in unamended soils. Although the correlations between RLD and soluble C were not significant at every sampling date, the August 2003 data do suggest a possible effect of roots on soluble C. In addition, significant correlations between soluble C and soluble P at several sampling dates suggest a relationship between these parameters. Therefore cropping systems that include crops with higher amounts of root growth may promote increased soluble soil C levels and enhance P bioavailability.     

Influence of Plant Root Exudates on the Mobility of Fuel Volatile Compounds in Contaminated Soils

Vegetation and its associated microorganisms play an important role in the behaviour of soil contaminants. One of the most important elements is root exudation, since it can affect the mobility, and therefore, the bioavailability of soil contaminants. In this study, we evaluated the influence of root exudates on the mobility of fuel derived compounds in contaminated soils. Samples of humic acid, montmorillonite, and an A horizon from an alumi-umbric Cambisol were contaminated with volatile contaminants present in fuel: oxygenates (MTBE and ETBE) and monoaromatic compounds (benzene, toluene, ethylbenzene and xylene). Natural root exudates obtained from Holcus lanatus and Cytisus striatus and ten artificial exudates (components frequently found in natural exudates) were added to the samples, individually and as a mixture, to evaluate their effects on contaminant mobility. Fuel compounds were analyzed by headspace-gas chromatography-mass spectrometry. In general, the addition of natural and artificial exudates increased the mobility of all contaminants in humic acid. In A horizon and montmorillonite, natural or artificial exudates (as a mixture) decreased the contaminant mobility. However, artificial exudates individually had different effects: carboxylic components increased and phenolic components decreased the contaminant mobility. These results established a base for developing and improving phytoremediation processes of fuel-contaminated soils.     

Elongation of barley roots in high‐pH nutrient solution is supported by both cell proliferation and differentiation in the root apex

Many crops grow well on neutral or weakly acidic soils. The ability of roots to elongate under high‐external pH would be advantageous for the survival of plants on alkaline soil. We found that root elongation was promoted in some plant species in alkaline‐nutrient solution. Barley, but not tomato, root growth was maintained in pH 8 nutrient solution. Fe and Mn were absorbed well from the pH 8 nutrient solution by both barley and tomato plants, suggesting that the different growth responses of these two species may not be caused by insolubilization of transition metals. The ability of intact barley and tomato plants to acidify external solution was comparable; in both species, this ability decreased in plants exposed to pH 8 nutrient solution for 1 w. Conversely, cell proliferation and elongation in barley root apices were facilitated at pH 8 as shown by microscopy and cell‐cycle‐related gene‐expression data; this was not observed in tomato. We propose that barley adapts to alkaline stress by increasing root development.