Plant growth and soil microbial community structure of legumes and grasses grown in monoculture or mixture

A greenhouse pot experiment was conducted to investigate the in?uence of soil moisture content on plant growth and the rhizosphere microbial community structure of four plant species (white clover, alfalfa, sudan grass, tall fescue), grown individually or in a mixture. The soil moisture content was adjusted to 55% or 80% water holding capacity (WHC). The results indicated that the total plant biomass of one pot was lower at 55% WHC. At a given soil moisture, the total plant biomass of white clover and tall ...     

Variations between rice cultivars in iron and manganese plaque on roots and the relation with plant cadmium uptake

To understand certain mechanisms causing variations between rice cultivars with regard to cadmium uptake and tolerance, pot soil experiments were conducted with two rice cultivars of di erent genotypes under di erent soil Cd levels. The relationships between plant Cd uptake and iron/manganese (Fe/Mn) plaque formation on roots were investigated. The results showed that rice cultivars di ered markedly in Cd uptake and tolerance. Under soil Cd treatments, Cd concentrations and accumulations in the cultivar Shanyou 63 (the genotype indica) were significantly higher than those in the cultivar Wuyunjing 7 (the genotype japonica) (P < 0.01, or P < 0.05), and Shanyou 63 was more sensitive to Cd toxicity than Wuyunjing 7. The di erences between the rice cultivars were the largest at relatively low soil Cd level (i.e., 10 mg/kg). Fe concentrations in dithionite-citrate-bicarbonate root extracts of Shanyou 63 were generally lower than that of Wuyunjing 7, and the di erence was the most significant under the treatment of 10 mg Cd/kg soil. The results indicated that the formation of iron plaque on rice roots could act as a barrier to soil Cd toxicity, and may be a “bu er” or a “reservoir” which could reduce Cd uptake into rice roots. And the plaque may contribute, to some extent, to the genotypic di erences of rice cultivars in Cd uptake and tolerance.     

Tracing the behaviour of hexachlorobenzene in a paddy soil-rice system over a growth season

Hexachlorobenzene (HCB), a persistent organic pollutant (POP), has been found in paddy soils. To improve the understanding of HCB contamination in paddy soils, a laboratory simulative study was carried out to investigate the behavior of HCB in a paddy soil and rice plants. This study was divided into three experiments. First, an experiment aimed to examine the evaporation of HCB in paddy soil. In the second experiment, rice was planted in 10 mg/kg HCB contaminated soil and after pot culture at 3, 6, 9, and 27 weeks (at maturity), both soil and plant samplings were scheduled to be sampled. The soil samples comprised rhizosphere soil, nonrhizosphere soil, and unplanted contaminated soil, whereas plant samples included shoots, roots, and rice grains (dehusked). Lastly, in this part, HCB in xylem saps was designed to be examined. The results showed that (1) the HCB translocation from paddy soil to rice by vaporization; (2) the HCB concentration in rice grains was surprisingly high; (3) the observed HCB decrease in rice rhizosphere offers a potential means for in situ HCB degradation; (4) HCB might not be transported along transpiration in rice.     

Distribution of cadmium in oilseed rape and Indian mustard grown on cadmium contaminated soil

Heavy metal distribution in the specialized accumulating plants was important for phytoextraction technique. Hydroponic and pot experiment were conducted to investigated Cd phytoextraction ability and Cd distribution in the plant of oilseed rape species. The results showed that oilseed rape Chuanyou Ⅱ-10 was more effective in phytoexetraction Cd among 21 varieties of oilseed rape and indicator plant Indian mustard. Cd concentration in the shoot of Chuanyou Ⅱ-10 and Indian mustard gradually decreased with an increase in growth period, while the amount of Cd uptake increased with the increase of growth period. There was constantly decrease in Cd concentration from the base leaves to the top leaves of Chuanyou Ⅱ-10 and Indian mustard, the percentages of Cd uptake in older leaves were higher than those of younger leaves. Older leaves of Chuanyou Ⅱ-10 and Indian mustard extracted more Cd for the Cd contamination soil, leaves should as far as possible develop before they reached the soil and the older leaves were harvested in priority.     

A win-win technique of stabilizing sand dune and purifying paper mill black-liquor

The principle and technique were reported here to produce lignin-based sand stabilizing material (LSSM) using extracted lignin from black liquor of straw paper mills. Field tests using LSSM to stabilize and green sand dunes were started in 2002. The field experiment was carried out in August 2005 when the newly formed plant community was 3 years old. The results from the comprehensive field experiment demonstrated that unlike polyvinyl acetate or foamed asphalt commonly used for dune stabilization, LSSM was plantfriendly material and could be used in combination with seeding and planting of desert species. With the help of LSSM, the desert species (i.e., Agriophyllum squarrosum (L.) Moq. and Artemisia desertorum Spreng. etc.) could be used to form community in 2–3 yeas and to stabilize sand dune e ectively. The newly formed community was sustainable under an extremely dry climate condition. The organic matter and total nitrogen in the soil increased significantly as the community were formed, while the change in P and K contents in the soil was negligible.     

Effect of water-driven changes in rice rhizosphere on Cd lability in three soils with different pH

Pot experiments were conducted to evaluate the effect of water management, namely continuous flooding (CF), intermittent flooding (IF) and non-flooding (NF), on Cd phytoavailaility in three paddy soils that differed in pH and in Cd concentrations. Diffusive gradients in thin films (DGT) technique was employed to monitor soil labile Cd and Fe concentrations simultaneously at three growth stages (tillering, heading and mature stage) of rice. The Cd phytoavailability were generally in the order of NF?>?IF?>?CF, and higher rice Cd (over permitted level, 0.2?mg/kg) were only found in neutral and acidic soils under NF conditions. DGT measured soil labile Cd rather than total Cd was the most reliable predictor for Cd accumulation in rice. CF enhanced the formation of root plaques, which related to oxidation of large quantities of available Fe on root surfaces due to the O₂ secretion of rice root. The Cd concentration in root plaques shared the same trend with DGT-Cd. Generally, root plaques would inhibit Cd uptake by rice under CF conditions, while under IF and NF conditions, root plaques act as a temporarily store of Cd, and soil labile Cd is the key factor that controls the transfer of Cd from soil to rice. The results of principle component analysis revealed that water management had the greatest effect on soil Cd lability and rice Cd in acidic soil. Thus, it is important to consider the availability of Cd and soil pH when assessing current agricultural practices of contaminated soil in China.     

Microbial activity related to N cycling in the rhizosphere of maize stressed by heavy metals

A greenhouse experiment was carried out to compare differences in potential activities of ammonification, nitrification and denitrification in rhizosphere and bulk soil in a heavy-metal-stressed system. Exchangeable fractions of Cd, Cu and Cr were all higher in the rhizosphere of maize than in bulk soil. Results showed that the mineralization of N in soil was stimulated by low concentration of Cd.Addition of Cd at low levels stimulated the ammonifying and nitrifying activity in soil, while inhibitory influences were shown at high levels.Nitrifying bacteria was proved to be the most sensitive one, whilst the effect on denitrifying bacteria was very limited. Comparing Cd, Cu and Cr(Ⅵ) at 20 mg/kg soil, Cd was the most effective inhibitor of ammonification and denitrification, while Cr(Ⅵ) had the strongest influence on nitrifying activity. Root exudates played important roles on the different exchangeable metal fractions and bacterial activities between rhizosphere and non-rhizosphere. Nitrate was the main form of mineral N in soil, as well as the main form of N absorbed by plants, but the formation and relative absorption of ammonium were promoted in response to high Cd exposure.     

Tolerance of Chrysantemum maximum to heavy metals: The potential for its use in the revegetation of tailings heaps

To find if ornamental plants are applicable to the remediation of metal-polluted areas, the tolerance of chrysanthemum plants (Chysanthemum maximum) var. Shasta to different metals under hydroponic conditions was studied. Their responses as influenced by the mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe BEG25 on substrates containing mine residues were also investigated. Our results showed that chrysanthemum is a metal-tolerant plant under hydroponic conditions, plants behaving as Pb-excluders, whereas Cd, Cu and Ni were accumulated in roots. Low accumulation in flowers was observed for Cd and Cu but it was concentration-dependent. Ni and Pb were not translocated to flowers. Shoot biomass was not significantly affected by the different rates of mine residue addition for both mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants accumulated less Pb and Cu in both shoots and roots than non-mycorrhizal plants. Chysanthemum could be a prospective plant for revegetation of tailings and the use of inoculation may decrease plant metal accumulation in polluted soils.     

Effects of several amendments on rice growth and uptake of copper and cadmium from a contaminated soil

Heavy metals in variable charge soil are highly bioavailable and easy to transfer into plants. Since it is impossible to completely eliminate rice planting on contaminated soils, some remediation and mitigation techniques are necessary to reduce metal bioavailability and uptake by rice. This pot experiment investigated the e ects of seven amendments on the growth of rice and uptake of heavy metals from a paddy soil that was contaminated by copper and cadmium. The best results were from the application of limestone that increased grain yield by 12.5–16.5 fold, and decreased Cu and Cd concentrations in grain by 23.0%–50.4%. Application of calcium magnesium phosphate, calcium silicate, pig manure, and peat also increased the grain yield by 0.3–15.3 fold, and e ectively decreased the Cu and Cd concentrations in grain. Cd concentration in grain was slightly reduced in the treatments of Chinese milk vetch and zinc sulfate. Concentrations of Cu and Cd in grain and straw were dependent on the available Cu and Cd in the soils, and soil available Cu and Cd were significantly a ected by the soil pH.     

Accumulation of cadmium and copper by female Oxya chinensis(Orthopera: Acridoidea) in soil-plant-insect system

One purpose of this research is to present accumulation of cadmium （Cd） and copper （Cu） by female Oxya chinensis （Orthopera： Acridoidea） in a simulated soil-plant-insect ecosystem treated with Cd. Fourth-instar nymphs of O. chinensis had been fed on wheat （Triticurn aestivum） seedlings contaminated with Cd and Cu for one month. In the ecosystem, the Cd concentration in wheat seedlings rose greatly with the increasing of Cd in the soil, but the Cu concentration in wheat seedlings was not found elevated. There was a highly significant difference（P〈0.05） in Cd concentrations of wheat seedlings and not any significant difference（P〉0.05） in Cu concentrations of wheat seedlings. The Cd and Cu concentration in different body part-head, thorax, abdomen, and hind femur, varied under different Cd concentrations in soil. There were significant differences （P〈0.05） in the four parts of Cd and Cu accumulations with all treatments. The order of Cd accumulation was thorax 〉abdomen 〉head 〉hind femur and the Cu was abdomen 〉thorax 〉 head〉hind femur. The results indicated that Cd and Cu were accumulated from the soil to grasshoppers through the plant; that is to say, Cd and Cu in environment could be transported to animal or human via food chain.     

镉超富集植物球果菜对镉-砷复合污染的反应及其吸收积累特征

采用室外盆栽模拟方法,比较和分析了镉（Cd）-砷（As）复合污染处理对球果菜（Rorippa globosa,十字花科焊菜属,1种从农田杂草中新发现的镉超富集植物）的生长及其对Cd、As吸收和积累特征的影响.结果表明,在低浓度Cd-As复合污染条件下,由于Cd、As的拮抗作用,从而促进植物的生长发育,同时也促进地上部对Cd的吸收和积累.在Cd-As复合污染处理浓度为10 mg/kg和50 mg/kg时,株高和地上部干重达到最大（分别为35.9 cm和2.2 g/盆）,叶片中Cd积累量高于同浓度单一Cd处理.Cd-As复合污染高浓度处理表现出对球果菜生长以及Cd的吸收和积累有协同的抑制作用.同时,球果菜根部对As的吸收能力大于其地上部,相应的富集系数≤0.3,转移系数≤0.6,说明球果菜对As有一定的排斥作用.这些结果表明,球果菜有很强的忍耐Cd-As复合污染的能力,对修复Cd-As复合污染土壤具有一定的潜力.     

改良剂对污染土壤上蔬菜生长及吸收重金属的影响

通过盆栽试验研究了石灰、钙镁磷肥、海泡石3种改良剂对重金属As、Cd、Pb和Zn复合污染土壤上蔬菜生长及其吸收重金属的影响,并表征了土壤有效态重金属含量、pH及脲酶活性等指标变化。研究结果表明,施加石灰和钙镁磷肥可以促进蔬菜生长,其中,石灰处理下小白菜生物量较对照提高了99.0%;石灰和钙镁磷肥处理下,西红柿茎叶生物量分别比对照提高了80.7%和82.3%。施用改良剂提高了土壤pH和脲酶活性,土壤有效态重金属含量不同程度降低,特别是海泡石的后期修复效果明显。与对照相比,石灰和钙镁磷肥处理显著降低小白菜叶中As含量,明显抑制西红柿茎叶对As、Cd和Pb的吸收(p<0.05);施加石灰明显降低小白菜叶中Cd和Pb含量(p<0.05)。然而,海泡石对抑制蔬菜吸收重金属的效果不明显。石灰和钙镁磷肥能有效抑制重金属从蔬菜根部向地上部转运,可作为重金属污染土壤上种植农作物优先考虑施用的改良剂。     

外加不同铁源和丛枝菌根对砷污染土壤上玉米生长及磷、砷吸收的影响

通过盆栽模拟试验研究了添加不同铁源及接种丛枝菌根真菌(Arbuecular mycorrhizal fungi,AMF)对高砷污染土壤上玉米生长及其吸收磷、砷、铁、锰、铜和锌的影响.试验结果表明,与对照相比,添加硫酸亚铁并接种AMF显著地提高了土壤有效铁、锰含量,降低了土壤中水溶性砷、磷含量以及玉米地上部砷的含量,并极大地增加了植株对磷的吸收,提高了植株体内磷砷吸收量之比,从而明显地改善了植株的菌根建成和生长状况.在不接种情况下,硫酸亚铁和石灰混合处理显著地降低了土壤水溶性砷、磷含量及根系砷含量,并明显增加了磷的吸收以及磷、砷吸收量的比值,使玉米植株生物量和根长增加的幅度较其它铁源处理时更大.尽管添加铁尾矿砂增加了土壤水溶性磷的含量以及植株磷的吸收而在一定程度上改善了玉米的生长,但这种效果以不接种时更为明显,因而有必要根据土壤的污染程度调整铁尾矿砂的添加量和接种抗性菌株,以强化植物的抗砷能力.     

Effects of arbuscular mycorrhizal fungi inoculation on arsenic accumulation by tobacco (Nicotiana tabacum L.)

A pot experiment was conducted to study the e ects of arbuscular mycorrhizal (AM) fungi (from contaminated or uncontaminated soils) on arsenic (As) uptake of tobacco (Nicotiana tabacum L.) in As-contaminated soil. Mycorrhizal colonization rate, dry weight, As and P uptake by plants, concentrations of water-extractable As and As fractions were determined. A low mycorrhizal colonization rate (< 25%) was detected. Our research indicated that AM fungi isolated from polluted soils were no more e ective than those from unpolluted soils when grown in symbiosis with tobacco. No significant di erences were observed in roots and stalks dry weights among all treatments. Leaves and total plant dry weights were much higher in Glomus versiforme treatment than that in control treatment. As contents in roots and stalks from mycorrhizal treatments were much lower than that from control treatment. Total plant As content exhibited the same trend. P concentrations in tobacco were not a ected by colonization, nor were stalks, leaves and total plant P contents. Roots P contents were remarkably lower in HN treatments than in other treatments. Meanwhile, decreased soil pH and lower water-extractable As concentrations and higher levels of As fraction bound to well-crystallized hydrous oxides of Fe and Al were found in mycorrhizal treatments than in controls. The protective e ect of mycorrhiza against plant As uptake may be associated with changes in As solubility mediated by changing soil pH. These results indicated that under As stress, proper mechanisms employed by AM fungi can protect tobacco against As uptake. Results confirmed that AM fungi can play an important role in food quality and safety.     

旺盛期烟草对镉富集敏感性研究

采用盆栽试验方法,揭示了旺盛期烟草（云烟99）对镉的富集特点以及光合等生理指标对镉胁迫的响应.结果表明：当土壤镉含量分别为4.43,7.94,17.33和49.79mg/kg时,烟草茎、叶及地上部镉的富集系数（植物镉含量与土壤镉含量的比值）均大于1,转移系数（地上部镉含量与根镉含量的比值）也大于1,但镉含量未达到镉超富集植物的临界含量标准100mg/kg.当土壤镉含量为4.43mg/kg时,烟草的耐性较强.当土壤镉含量大于7.94mg/kg时,烟草的生物量、叶片光合色素含量、净光合速率、蒸腾速率、气孔导度和SOD活性均显著下降（P<0.05）,胞间CO₂浓度和MDA含量显著提高（P<0.05）.旺盛期烟草对镉富集比较敏感,建议烟草的种植要远离镉污染土壤或镉背景值较高的土壤.     

印度芥菜和油菜互作对各自吸收土壤中难溶态镉的影响

在石灰性土壤加入CdCO3条件下 ,通过温室土培盆栽试验研究印度芥菜和油菜互作对各自吸收土壤中难溶态镉的影响 .试验结果表明 ,印度芥菜和油菜互作时 ,印度芥菜对养分的竞争能力强 ,地上部干重高于单作时的 ;而与之互作的油菜由于根际土壤溶液中的有效态镉含量增加或对养分的竞争能力弱 ,地上部干重低于单作时的 .印度芥菜的根系有很强的活化能力 ,和油菜互作时可提高植物提取修复难溶态镉污染土壤的能力 ,和单作相比 ,互作对印度芥菜吸收镉的能力无显著影响 ,但却可以显著增加油菜植株体内的镉含量 ,在土壤相同镉量的条件下 ,印度芥菜和油菜互作时植株的吸镉量和对土壤的净化率均高于单作     

萝卜对邻苯二甲酸酯(PAEs)吸收累积特征及途径的初步研究

利用玻璃室处理和覆土处理(人工污染土壤上覆盖原土壤)的方法控制萝卜的PAEs来源进行盆栽试验,试验处理分别为:(1)原土壤,暴露于大气中(空白1);(2)原土壤,置于玻璃室中(空白2);(3)人工污染土壤,暴露于大气中;(4)人工污染土壤,置于玻璃室中;(5)人工污染土壤上覆盖2 cm厚原土壤,暴露于大气中;(6)人工污染土壤上覆盖2 cm厚原土壤,置于玻璃室中.盆栽后应用GC/MS对土壤和植株样品中的PAEs进行分析,初步研究了萝卜对PAEs的吸收累积特征及途径.研究结果表明,萝卜茎叶和直根中邻苯二甲酸二乙酯(DEP)的含量均低于检测限,邻苯二甲酸正二丁酯(DBP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)的含量与土壤污染浓度成正相关关系,DBP的含量高于DE-HP,两者主要分布在茎叶中.未覆土处理与覆土处理相比,前者盆栽的萝卜茎叶中DBP和DEHP的含量均高于后者,但在2个处理之间差异不显著,表明萝卜茎叶可以吸收污染土壤中挥发出来的DBP和DEHP,但直根吸收运移是茎叶中DBP和DEHP的主要来源途径.玻璃室处理导致萝卜茎叶中DBP含量的提高,在大棚蔬菜生产中值得注意.     

颗粒有机质对水稻镉吸收及转运的影响

采用盆栽试验,通过测定不同颗粒有机质(POM)添加量下土壤、POM中有机碳(POM-C)和Cd(POM-Cd)含量及水稻各部位Cd含量,研究了POM对紫色水稻土水稻镉吸收的影响及机制.结果表明:添加POM提高了土壤有机碳(SOC)、溶解性有机碳(DOC)、POM-C、POM-Cd、POM对Cd的富集系数和土壤有效Cd含量,在POM添加量达2. 5 g·kg~(-1)时可显著提高土壤POM-C和POM-Cd比例.添加POM提高了水稻植株生物量及Cd在水稻植株中的总累积量,但使水稻根Cd含量降低24%～42%,茎叶Cd含量提高9%～30%,籽粒Cd含量在POM添加量为0. 5 g·kg~(-1)和1. 0 g·kg~(-1)时分别降低了17%和36%,添加量为2. 5 g·kg~(-1)时提高了39%.添加POM对Cd在水稻根和茎叶中的分配不显著,但POM添加量较少时可抑制Cd从水稻茎叶向籽粒转运,POM添加达到一定量时,促进Cd从茎叶向籽粒转运,最终提高籽粒中Cd含量.相关分析结果表明,土壤有效Cd是影响茎叶Cd累积的主要因素,POM-Cd总量是影响籽粒中Cd累积的主要因素.因此,添加POM可通过改变土壤SOC、DOC、POM-C、POM-Cd及有效镉含量,影响水稻对Cd的吸收.     

EDDS对土壤铜镉有效性及蓖麻吸收转运的影响

为探究螯合剂对植物吸收重金属的影响,以蓖麻（Ricinus communis L.）为供试植物,通过土培和盆栽试验,研究不同含量乙二胺二琥珀酸（EDDS）对土壤中铜镉形态和植物吸收、转运的影响.结果表明,EDDS显著增加了土壤有效态铜和镉含量,培养15 d时,增幅分别为43.01%~103.55%和51.78%~69.43%,同时促进了可还原态铜向弱酸提取态转化,增加了土壤铜的移动性.EDDS促进了蓖麻对铜的吸收、转运与富集.EDDS 2.5和EDDS 5.0处理时,地上部铜含量是对照的4.88倍和16.65倍（P< 0.05）,根部是对照的2.89倍和3.60倍（P<0.05）,铜转运系数显著提高了72.73%和381.82%.EDDS 5.0处理时,蓖麻地上部和根部的铜提取量分别是对照处理的14.08倍和2.16倍,总铜提取量是对照处理的4.70倍（P< 0.05）.此外,EDDS显著增加了蓖麻镉含量,EDDS 2.5处理时,地上部和根部分别增加了15.15%和57.42%,蓖麻总镉提取量显著提高了13.44%.综上可知,EDDS能增加土壤铜镉的有效性,促进蓖麻对铜镉的吸收,提高蓖麻的修复效率,其中5.0 mmol·kg^-1 EDDS更有利于蓖麻对铜的提取,而2.5 mmol·kg^-1 EDDS处理对镉的提取有较高的增加效果.     

Growth responses of the newly-discovered Cd-hyperaccumulator Rorippa globosa and its accumulation characteristics of Cd and As under joint stress of Cd and As

Rorippa globosa has been identified as a newly-found Cd-hyperaccumulating species. In the present study, growth responses of Rorippa globosa and its accumulation characteristics of Cd and As were examined under joint stress of Cd and As. The results showed that Cd and As had an antagonistic effect on enhancing the growth of Rorippa globosa plants and Cd uptake and accumulation under the low concentration Cd and As treatments. When the concentration of Cd in the soil was 10 mg/kg and the concentration of As was 50 mg/kg, the highest growing height of the plant was up to 35.9 cm and the dry weight of the shoots was up to 2.2 g/pot, respectively. Meanwhile, the accumulation of Cd in the leaves under the joint stress was higher than that at the same level under single Cd pollution. However, there were synergic adverse effects on plant growth and Cd uptake under the combined pollution from a high concentration of Cd and As. Meanwhile, the accumulation of As in the roots was greater than that in the shoots, the translocation factor (TF) was ⩽0.3 and the bioaccumulation factor (BF) was ⩽0.6, thus showing that Rorippa globosa had an excluding effect on As uptake. These results confirmed that Rorippa globosa had a strong tolerant ability to the joint stress of Cd and As, and the potential for phytoremediation of soils contaminated by Cd and As. Translated from Environmental Science, 2007, 28(6) [译自: 环境科学]