产酸内生菌荧光假单胞菌R1对东南景天生长和吸收、积累土壤中重金属锌镉的影响

研究了从东南景天（Sedum alfredii）的根系分离和纯化的内生菌荧光假单胞菌（Pseudomonas fluorescens）R1（菌株R1）在溶解氧化锌（ZnO）和氧化镉（CdO）过程中的生长代谢特征,分析了代谢产物中有机酸的组成及含量;通过盆栽实验,进一步探讨了土壤接种菌株R1对东南景天的生长、吸收和积累锌、镉的影响。结果发现,菌株R1在生长代谢过程中分泌苹果酸、琥珀酸、乙酸、柠檬酸、草酸等有机酸是导致ZnO和CdO溶解的主要原因,且反应体系中增加ZnO和CdO能够提高有机酸的分泌量,加速ZnO和CdO的溶解。菌株R1接种到未灭菌或灭菌的锌、镉污染土壤中均能在一定程度上促进东南景天的生长和吸收Zn、Cd。在未灭菌ZnO土壤上,接种菌株R1使东南景天根系和地上部的干物质质量、地上部Zn积累量分别增加了15.56%、9.74%和29.84%;在灭菌ZnO土壤上,接种菌株R1使东南景天地上部的干物质质量和Zn积累量分别增加9.56%和8.97%。在未灭菌CdO土壤上,接种菌株R1使东南景天根系和地上部的干物质质量、地上部Cd积累量分别增加30.30%、6.15%和27.21%;在灭菌CdO土壤上,接种菌株R1使东南景天根系和地上部的干物质质量、地上部Cd积累量分别增加5.08%、8.82%和26.14%。     

氮素形态对烟草根际镉的有效性及镉吸收的影响

采用盆栽实验,研究了不同氮素形态对酸性紫色土和中性紫色土中烟草根际有效镉含量及烟草吸收镉的影响。结果表明,氮素形态对烟草根际有效镉含量的影响不显著,但铵态氮(AN)和铵态氮+硝化抑制剂双氰胺(AN+DCD)使非根际有效镉含量显著提高。2种土壤中,烟草的生物量均以AN+DCD处理最高;烟草地上部镉含量在酸性紫色土中以硝态氮(NN)处理最高,中性紫色土中则以AN+DCD处理最高;烟草地上部镉累积量均以AN+DCD和AN+NN处理最高。从植物修复角度,2种土壤宜以铵态氮与硝态氮混合或铵态氮与双氰胺混合方式施用。     

超积累植物东南景天热解过程中Cd的迁移转化规律及炭产物安全利用研究

在管式炉对Cd超积累植物东南景天(Sedum alfredii)进行热解,研究热解过程中Cd的迁移和形态转化,并在最佳温度条件下探究制备的东南景天生物炭对Cd的吸附作用。结果表明,随着温度上升,生物炭产率下降,挥发分增加;温度能影响Cd在气、液、固三相中的分布,温度升高能明显促进重金属由固相向气相迁移;生物炭中Cd形态受温度影响,随温度升高,对环境影响较大的水溶态和酸溶态Cd含量呈现出降低趋势,在700℃以上时,大部分Cd是以稳定的可氧化态、可还原态以及残渣态形式存在;800℃热解得到的东南景天生物炭对Cd具有一定的吸附效果,最高吸附量达到28.7mg/g。通过合理控制热解温度能够实现炭产物的稳定化,并可安全利用到重金属污染水体或者农田污染治理中。     

不同粒径生物炭和泥鳅对人工湿地植物根系形态及基质硝化与反硝化能力的影响

向人工湿地中加入2种粒径（粒径1～2 mm和粒径<1 mm）生物炭和泥鳅,研究了不同粒径生物炭和泥鳅对湿地植物根系形态和基质硝化与反硝化强度的影响。结果表明,向人工湿地中加入泥鳅和生物炭,降低了基质的氨态氮含量,增加基质的硝态氮含量、硝化强度和反硝化强度;与粒径小(<1 mm)的生物炭相比,添加粒径大(1～2 mm)的生物炭后,湿地基质的氨态氮含量、硝态氮含量和反硝化强度分别降低了46.6%、51.1%和35.4%。加入生物炭和泥鳅均增加了湿地植物总根长和总根体积,然而与粒径小的生物炭相比,添加粒径大的生物炭后,人工湿地中植物总根长和总根体积分别降低了15.1%和6.8%。基质硝态氮含量与人工湿地中植物总根长和总根体积分别呈显著相关关系（α = 0.01）。结果表明,生物炭提高了人工湿地基质硝化强度,有利于硝态氮的生成,促进人工湿地中植物根的生长,增加了总根长和总根体积。     

促生内生菌假单胞菌Ⅱ8L4的GFPuv标记及其侵染东南景天的特征

绿色荧光蛋白标记法是研究内生细菌和宿主互作的重要手段。采用热激法将含有绿色荧光蛋白基因的质粒pDSK-GFPuv导入超积累植物东南景天叶片分离和纯化的、具有促植物生长特性的Zn、Cd抗性内生细菌假单胞菌Ⅱ8L4,获得了具有良好发光表现型的荧光标记菌株Ⅱ8L4-GFPuv-A。GFPuv基因在标记菌株Ⅱ8L4-GFPuv-A中不仅可以稳定表达,且标记菌株保持了野生型菌株的促植物生长特征,其分泌IAA和高铁载体、溶解无机磷的能力与野生型菌株之间没有显著差异,但标记菌株Ⅱ8L4-GFPuv-A对Zn、Cd的抗性水平有所降低。借助激光共聚焦显微镜荧光观察发现,标记菌株Ⅱ8L4-GFPuv-A可从东南景天茎扦插苗的伤口处和芽点侵入,并大量迁移至维管束木质部的细胞间隙;标记菌株Ⅱ8L4-GFPuv-A还可以从根表或根毛侵入根系,并迁移和定殖于根系的维管束内。     

冻融循环及有机肥配施对黑土中镉形态的影响

以黑龙江黑土为对象,研究了冻融循环及有机肥配施量对黑土中镉形态分布的影响。对配施不同有机肥的土壤样品进行5次冻融循环,采用电感耦合等离子质谱仪(ICP-MS)分析土壤样品中镉的赋存形态。结果表明,冻融循环数及有机肥的配施有助于降低黑土中的总镉量;冻融循环会促使黑土中的镉由交换态、碳酸盐结合态、有机结合态向铁锰氧化物结合态和残渣态转化,而增加有机肥配施量会使黑土中的镉由交换态向其他形态转化。因此,冻融循环及有机肥配施有助于降低土壤中镉的生物有效性,进而降低其环境风险。     

3种水培植物根系分泌的有机酸对氮循环菌的影响

通过收集水培吊兰、空心菜和水芹的根系分泌物,采用液相色谱分析了其中有机酸的种类和含量;并研究了根系分泌物中的有机酸对氮循环菌的影响。结果表明3,种植物根系分泌物中的有机酸对氨化细菌和反硝化细菌的生长具有促进作用,对亚硝化细菌和硝化细菌的生长具有抑制作用。     

植物及其根系分泌物对污水净化效果的影响

为了弄清不同植物对污水的净化效率以及其根系分泌物对污水净化效果的影响,对植物根系分泌物与脱氮及COD去除之间的关系进行了研究。结果表明,在净化时间相同的情况下,茭白（Zizania cadaciflora）对污水COD的去除效果要好于美人蕉（Canna generalis）,美人蕉对污水TN的去除率要高于茭白,系统中N去除主要依靠硝化反硝化脱氮;美人蕉根系比茭白根系能分泌更多的溶解有机碳（DOC）,这些可溶性的有机碳可以为污水中微生物提供碳源,有利于氮的反硝化去除,但同时也会增加出水COD的浓度。而茭白比美人蕉具有更强的硝化能力,可促进其硝化反硝化作用。     

外源钙对镉胁迫下苎麻生长及生理代谢的影响

以苎麻为实验材料,采取营养液栽培方式,研究了不同浓度的钙(0、1、5和10 mmol·L-1)在5 mg·L-1 氯化镉胁迫下,对苎麻幼苗生长及植物体内重金属的积累、光合作用、抗氧化作用等的影响。研究结果显示,中浓度钙处理(5 mmol·L-1)能明显缓解镉胁迫对苎麻的毒害作用。与单独镉处理相比,外源5 mmol·L-1钙处理苎麻地上部分和根部的生物量分别为单独镉胁迫下的1.21倍和1.32倍,叶绿素含量增加了19.77%,丙二醛和过氧化氢含量分别下降了19.09%和29.02%,抗氧化酶的活性也发生了相应变化;低浓度钙处理(1 mmol·L-1)显著提高了苎麻茎叶中镉的含量,分别为单独镉胁迫下的2.54倍和3.59倍。由此表明,外源钙和镉的交互作用与外源钙的浓度密切相关。     

添加天然沸石和石灰对土壤镉形态转化的影响

采用土壤培养实验,研究镉污染土壤中添加沸石、石灰及两者配施对土壤pH值和土壤镉形态变化的影响。结果表明,土壤pH值随沸石用量的增加而增加,随培养时间呈现先增加后下降并逐渐趋于稳定的趋势,但均高于对照。高剂量石灰的处理对土壤pH的影响最大,与对照相比土壤pH提高了3.33个单位。在土壤5~50 d培养过程中,石灰处理的土壤交换态镉含量呈现先逐渐降低而后略有升高的趋势,其余处理均呈下降趋势。培养50 d后,高剂量的沸石、石灰及高剂量沸石与石灰配施处理的土壤交换态镉含量从5 d时的67.54、61.95和55.56 mg/kg降低至54.65、49.93和45.96mg/kg。相关分析表明,不同培养时期交换态镉含量与土壤pH值呈负相关关系。在10个处理中,L2Z3(石灰2 g/kg土和沸石60 g/kg土)组合处理效果最好,使土壤交换态镉含量下降了34.68%,碳酸盐结合态镉含量上升了4.30%,铁锰氧化结合态镉含量上升了16.97%,有机结合态镉含量上升了1.31%,残渣态镉含量上升了12.11%。     

Calcium protects roots of Sedum alfredii H. against cadmium-induced oxidative stress

Sedum alfredii is a well-known Cd (cadmium) hyperaccumulator native to China. The impacts of exogenous Ca on Cd-induced oxidative stress and antioxidant systems in roots of S. alfredii were investigated by using cellular and biochemical approaches. Supplementation of the medium with higher Ca levels resulted in alleviated growth inhibition and decreased Cd concentration, as well as increased Ca concentration in roots. Cadmium induced lipid peroxidation and loss of plasma membrane integrity, reactive oxygen species overproduction, as well as ultrastructural changes of root cells were largely reversed by Ca supplementation in the medium. Calcium application significantly altered the Cd effects on antioxidant enzymes and non-enzyme antioxidants (non-protein thiols), and significantly increased glutathione (GSH) biosynthesis. The results suggest that Ca is able to protect the roots of S. alfredii against Cd toxicity by restoration of Cd-displaced Ca, alleviation of the metal induced oxidative stress, as well as promotion of GSH biosynthesis.     

The impact of EDTA on lead distribution and speciation in the accumulator Sedum alfredii by synchrotron X-ray investigation

The in vivo localization and speciation of lead (Pb) in tissues of the accumulator Sedum alfredii grown in EDTA-Pb and Pb(NO₃)₂ was studied by synchrotron X-ray investigation. The presence of EDTA-Pb in solution resulted in a significant reduction of Pb accumulation in S. alfredii. Lead was preferentially localized in the vascular bundles regardless of treatments but the intensities of Pb were lower in the plants treated with EDTA. Lead was predominantly presented as a Pb-cell wall complex in the plants regardless of its supply form. However, a relatively high proportion of Pb was observed as Pb-EDTA complex when the plant was treated with EDTA-Pb, but as a mixture of Pb₃(PO₄)₂, Pb-malic, and Pb-GSH when cultured with ionic Pb. These results suggest that EDTA does not increase the internal mobility of Pb, although the soluble Pb-EDTA complex could be transported and accumulated within the plants of S. alfredii.     

Arbuscular mycorrhizal fungi induced differential Cd and P phytoavailability via intercropping of upland kangkong (Ipomoea aquatica Forsk.) with Alfred stonecrop (Sedum alfredii Hance): post-harvest study

A post-harvest experiment was conducted further to our previous greenhouse pot study on upland kangkong (Ipomoea aquatica Forsk.) and Alfred stonecrop (Sedum alfredii Hance) intercropping system in Cd-contaminated soil inoculated with arbuscular mycorrhizal (AM) fungi. Previously, four treatments were established in the intercropping experiment, including monoculture of kangkong (control), intercropping with stonecrop (IS), and IS plus inoculation with Glomus caledonium (IS?+?Gc) or Glomus versiforme (IS?+?Gv). Both kangkong and stonecrop plants were harvested after growing for 8 weeks. Then, the tested soils were reclaimed for growing post-harvest kangkong for 6 weeks. In the post-harvest experiment, there were no significant differences between the IS and control treatments, except for a significantly decreased (p?<?0.05) soil available P concentration with IS treatment. Compared with IS, both IS?+?Gc and IS?+?Gv significantly decreased (p?<?0.05) soil DTPA-extractable (phytoavailable) Cd concentrations, but not total Cd, by elevating soil pH, causing significantly lower (p?<?0.05) Cd concentrations in both the root and shoot of kangkong. In addition, both Gc and Gv significantly increased (p?<?0.05) soil acid phosphatase activities and available P concentrations and hence resulted in significantly higher (p?<?0.05) plant P acquisitions. However, only Gv significantly increased (p?<?0.05) kangkong yield, while Gc only significantly elevated (p?<?0.05) the shoot P concentration. It suggested that AM fungi have played key roles in Cd stabilization and P mobilization in the intercropping system, and such positive responses seemed to be sustainable and valuable in post-harvest soils.     

Effects of high atmospheric CO2 concentration on root hydraulic conductivity of conifers depend on species identity and inorganic nitrogen source

We examined root hydraulic conductivity (L_p) responses of one-year-old seedlings of four conifers to the combined effects of elevated CO₂ and inorganic nitrogen (N) sources. We found marked interspecific differences in L_p responses to high CO₂ ranging from a 37% increase in P. abies to a 27% decrease in P. menziesii, but these effects depended on N source. The results indicate that CO₂ effects on root water transport may be coupled to leaf area responses under nitrate (NO₃⁻), but not ammonium (NH₄⁺) dominated soils. To our knowledge, this is the first study that highlights the role of inorganic N source and species identity as critical factors that determine plant hydraulic responses to rising atmospheric CO₂ levels. The results have important implications for understanding root biology in a changing climate and for models designed to predict feedbacks between rising atmospheric CO₂, N deposition, and ecohydrology.     

Influences of salinity on the biokinetics of Cd, Se, and Zn in the intertidal mudskipper Periophthalmus cantonensis

The biokinetics (aqueous uptake, dietary assimilation, and elimination) of Cd, Se, and Zn in the intertidal mudskipper, Periophthalmus cantonensis, were examined at different acclimated salinities using the radiotracer technique. The dietary assimilation efficiency from ingested radiolabeled polychaetes was the highest for Se (32–40%), followed by Zn (5–7%) and Cd (2–3%), and was not influenced by salinity within a range of 10–30 psu. Uptake from the dissolved phase typically exhibited a linear pattern within the first 12 h of exposure, followed by a second slower uptake. The highest concentration factor (CF) was found for Zn, followed by Cd and Se. Differences in salinity did not significantly affect the CF of the three metals within the first 12 h, but the CFs were significantly higher at lower salinities (10–20 psu) than at the highest salinity (30 psu) by the end of 48 h exposure. Because the degrees to which the uptake of Se (a metalloid) and Cd/Zn were affected by salinity were comparable, we concluded that metal speciation as a result of salinity change was not important in leading to a change in metal CF. Physiological changes may be responsible for the increasing uptake at lowered salinity. The elimination rates of the three metals (0.01–0.06 d⁻¹) were not significantly affected by salinity, but Se was eliminated at a faster rate following aqueous uptake than following dietary ingestion. There was no consistent influence of exposure routes on Cd and Zn elimination. The accumulated Cd was mainly associated with the gut, whereas the muscle was the dominant target site for Se and Zn accumulation.     

赤泥添加对石灰性土壤中Pb、Cd形态分布及小麦根系的影响

通过田间种植小麦实验,研究添加不同剂量拜耳赤泥（0%、1%、2%、3%、4%和5%）对重金属污染的石灰性土壤Pb、Cd化学形态和小麦幼苗根系的影响。培养1个月,添加赤泥显著地提高了土壤pH值,提高幅度随赤泥投加量增加而增大。培养3个月,添加不同剂量的赤泥均明显降低土壤中可交换态Pb和Cd的含量,赤泥投加量为5%时效果最为显著,分别比对照下降90%和72%。添加赤泥对所种植小麦幼苗的根系也有影响。种植5个月,小麦根系总根长、总表面积和总体积等随添加赤泥的剂量增加呈现先增大后减小的趋势,赤泥投加量为3%时增幅最大,总根长、总表面积和总体积分别比对照增加88.23%、75%和90.32%。研究表明,赤泥可作为重金属污染的石灰性土壤的理想改良剂,但考虑到小剂量赤泥（即1%~3%）促进重金属污染农田中小麦根系的生长,建议在种植区采用小剂量赤泥（即3%）处理的重金属污染修复方案。     

Effect of population density on growth, biomass and nickel accumulation capacity of Lemna gibba (Lemnaceae)

The effect of population densities on the growth rate and metal (nickel) accumulation capacity of Lemna gibba (Lemnaceae) was studied under laboratory conditions. At high population densities (800 or 1600 seedling per pot), we observed decreasing growth rate with increasing L. gibba density. Especially, at a density of 1600 seedling a pot the net growth rate became negative. This lower growth rate may relate to lower local temperatures and nutrients within L. gibba mats. Biomass production was inhibited by an increase in plant density. Additionally, high population densities caused decreasing nickel accumulation by L. gibba. In this study, a simple model was created according to data obtained from this study. The model has suggested that crowding is an important factor in limitation of growth of L. gibba.     

Effects of simultaneous ozone exposure and nitrogen loads on carbohydrate concentrations, biomass, and growth of young spruce trees (Picea abies)

Spruce saplings were grown under different nitrogen fertilization regimes in eight chamberless fumigation systems, which were fumigated with either charcoal-filtered (F) or ambient air (O3). After the third growing season trees were harvested for biomass and non-structural carbohydrate analysis. Nitrogen had an overall positive effect on the investigated plant parameters, resulting in increased shoot elongation, biomass production, fine root soluble carbohydrate concentrations, and also slightly increased starch concentrations of stems and roots. Only needle starch concentrations and fine root sugar alcohol concentrations were decreased. Ozone fumigation resulted in needle discolorations and affected most parameters negatively, including decreased shoot elongation and decreased starch concentrations in roots, stems, and needles. In fine roots, however, soluble carbohydrate concentrations remained unaffected or increased by ozone fumigation. The only significant interaction was an antagonistic effect on root starch concentrations, where higher nitrogen levels alleviated the negative impact of ozone.