Phytoremediation of arsenic and lead in contaminated soil using Chinese brake ferns (Pteris vittata) and Indian mustard (Brassica juncea)

Field and greenhouse experiments were performed to assess the performance of phytoremediation of arsenic and lead from contaminated soil at an EPA Superfund site (Barber Orchard). Chinese Brake ferns (Pteris vittata) were used to extract arsenic. On average, fern shoot arsenic concentrations were as high as 20 times the soil arsenic concentrations under field conditions. It was estimated that 8 years would be required to reduce the acid-extractable portion of soil arsenic to safe levels (40 mg/kg). The effect of soil pH on arsenic extraction was also investigated. Results indicate that increasing soil pH may improve arsenic removal. Indian mustard plants (Brassica juncea) were used under greenhouse conditions to phytoextract soil lead. EDTA was applied to soil and was found to improve lead extraction. When the EDTA concentration was 10 mmol EDTA/kg soil in soil containing 338 mg Pb/kg soil, mustard plants extracted approximately 32 mg of lead. In conclusion, phytoremediation would be a suitable alternative to conventional remediation techniques, especially for soils that do not require immediate remediation.     

Effect of Fluoride on Arsenic Uptake from Arsenic-Contaminated Groundwater using Pteris vittata L.

High-arsenic groundwater in inland basins usually contains high concentrations of fluoride. In the present study, the effects of fluoride on arsenic uptake by Pteris vittata and on arsenic transformation in growth media were investigated under greenhouse conditions. After P. vittata was hydroponically exposed to 66.8 μM As (V) in the presence of 1.05 mM F^? in the form of NaF, KF, or NaF+KF for 10 d, no visible toxicity symptoms were observed, and there were not significant differences in the dry biomass among the four treatments. The results showed that P. vittata tolerated F^? concentrations as high as 1.05 mM but did not accumulate fluoride in their own tissues. Arsenic uptake was inhibited in the presence of 1.05 mM F^?. However, in hydroponic batches with 60 μM As (III) or 65 μM As (V), it was found that 210.6 and 316.0 μM F^? promoted arsenic uptake. As(III) was oxidized to As(V) in the growth media in the presence and absence of plants, and F^? had no effect on the rate of As(III) transformation. These experiments demonstrated that P. vittata was a good candidate to remediate arsenic-contaminated groundwater in the presence of fluoride. Our results can be used to develop strategies to remediate As-F-contaminated water using P. vittata.     

Phytofiltration of arsenic-contaminated groundwater using Pteris vittata L.: effect of plant density and nitrogen and phosphorus levels

This field-scale hydroponic experiment investigated the effects of plant density and nutrient levels on arsenic (As) removal by the As-hyperaccumulator Pteris vittata L. (Chinese brake fern). All ferns were grown in plastic tanks containing 30 L of As-contaminated groundwater (130 microg x L(-1) As) collected from South Florida. The treatments consisted of four plant densities (zero, one, two, or four plants per 30 L), two nitrogen (N) concentrations (50% or 100% of 0.25-strength Hoagland solution [HS]), and two phosphorous (P) concentrations (15% and 30% of 0.25 strength HS). While low P was more effective than high P for plant As removal initially, N levels showed little effect. At 15% P, it took 3 wk for the ferns at a plant density of four to reduce As to less than 10 microg L(-1) (USEPA and WHO standard), whereas it took 4-6 wk at plant densities of one or two. For reused ferns, established plants with more extensive roots than "first-time" ferns, a low plant density of one plant/30 L was more effective, reducing As in water to less than 10 microg L(-1) in 8 h. This translates to an As removal rate of 400 microg h(-l) plant(-1), which is the highest rate reported to date. Arsenic-concentration in tanks with no plants as a control remained high throughout the experiment. Using more established ferns supplemented with dilute nutrients (0.25 HS with 25% N and 15% P) with optimized plant density (one plant per 30 L) reduced interplant competition and secondary contamination from nutrients, and can be recommended for phytofiltration of As-contaminated groundwater. This study demonstrated that P. vittata is effective in remediating As-contaminated groundwater to meet recommended standards.     

Distributions of arsenic and essential elements in pinna of arsenic hyperaccumulator Pteris vittata L.

The distributions of arsenic and 6 essential elements in the pinna of As hyperaccumulator, Pteris vittata L., were studied using synchrotron radiation X-ray fluorescence (SRXRF). Significant correlation between the distribution and mobility of the elements revealed that SRXRF study on the elemental distribution was feasible to inspect the transportations of elements in plants. The distribution of As in the pinna showed that As had great abilities to be transported in xylem vessels and from xylem to mesophyll. The distribution of K, one of the most mobile elements in plants, was similar to that of As, whereas the distributions of Fe and Ca with less mobility in plants were almost opposite to that of As in the pinna.     

Effects of Iron and Manganese Plaques on Arsenic Uptake by Rice Seedlings (Oryza sativa L.) Grown in Solution Culture Supplied with Arsenate and Arsenite

We have shown previously that phosphorus nutrition and iron plaque on the surface of rice roots influence arsenate uptake and translocation by rice in hydroponic culture. We have now investigated the role of iron (Fe) and manganese (Mn) plaque on arsenate and arsenite uptake and translocation in rice seedlings grown hydroponically. Fe and Mn plaques were clearly visible as reddish or brown coatings on the root surface after 12 h induction, and Fe plaque was much more apparent than Mn plaque. Arsenite or arsenate supply did not decrease plant dry weights significantly. There were significant differences in shoot dry weights but little difference in root dry weights between some plaque treatments. Arsenic (As) concentrations in Fe plaque when arsenate was supplied were significantly higher than those in no plaque (control) and Mn plaque treatments, and much higher than those supplied with arsenite. This showed that Fe plaque on the rice root had higher affinity to arsenate than to arsenite. In Fe plaque treatment, the results indicated that most As was sequestered in roots when arsenite was supplied and most As concentrated in Fe plaque when arsenate was supplied. Most As was accumulated in rice roots in Mn plaque and no plaque treatments for both As species.     

刈割对蜈蚣草的砷吸收和植物修复效率的影响

以野生苗移栽的蜈蚣草为试材 ,通过盆栽试验研究了收获次数对蜈蚣草生长、砷吸收和植物修复效率的影响。结果表明 :在 3次收获中 ,随着收获次数的增加 ,不同砷浓度处理之间蜈蚣草生物量的差异逐步缩小 ;不加砷的对照处理中 ,每次收获后的砷吸收速率下降趋势 ,而在 3个加砷处理中 ,第 2次收获和第 3次收获的蜈蚣草的吸砷速率为 6 3～ 75 μg/ (plant· d)、4 4～ 5 5μg/ (plant· d) ,均显著高于第 1次收获时的吸收速率。表明多次收获并没有降低砷的积累速度。由此可见 ,通过适当增加蜈蚣草的收获次数是提高砷修复效率的一种策略     

Suppression of the High Affinity Phosphate Uptake System: A Mechanism of Arsenate Tolerance in Holcus lanatus L.

In Holcus lanatus L. phosphate and arsenate are taken up bythe same transport system. Short-term uptake kinetics of thehigh affinity arsenate transport system were determined in excisedroots of arsenate-tolerant and non-tolerant genotypes. In tolerantplants the V_max of ion uptake in plants grown in phosphate-freemedia was decreased compared to non-tolerant plants, and theaffinity of the uptake system was lower than in the non-tolerantplants. Both the reduction in V_max and the increase in K_m ledto reduced arsenate influx into tolerant roots. When the twogenotypes were grown in nutrient solution containing high levelsof phosphate, there was little change in the uptake kineticsin tolerant plants. In non-tolerant plants, however, there wasa marked decrease in the V_max to the level of the tolerant plantsbut with little change in the K_m. This suggests that the lowrate of arsenate uptake over a wide range of differing rootphosphate status is due to loss of induction of the synthesisof the arsenate (phosphate) carrier. Key words: Arsenate, Holcus lanatus L., phosphate uptake, tolerance mechanisms, uptake mechanisms     

蜈蚣草砷超富集机制及其在砷污染修复中的应用

蕨类植物蜈蚣草能够从土壤中吸收砷,并储存于地上部分羽叶的液泡中。蜈蚣草具有高效的抗氧化系统,以降低砷的毒害;其砷酸还原系统和液泡区隔化是蜈蚣草进行砷解毒和砷超富集的重要机制。本文综述了目前蜈蚣草砷超富集机制研究的主要进展,并对其在修复砷污染环境的应用中进行了讨论。     

Clonal Diversity in Differently-Aged Populations of the Pseudo-Annual Clonal Plant Circaea lutetiana L.

Abstract: In many clonal plant species seedling recruitment is restricted to short colonization episodes early in the development of the population, and clonal diversity (i.e., genet diversity) in the population is expected to decrease with increasing population age. In established populations of the pseudo-annual Circaea lutetiana seedling recruitment has previously not been observed. Therefore, we expected established populations to have low clonal diversities. We analysed number and frequency of genets and spatial distribution of genets in six differently-aged C. lutetiana populations with the use of four informative RAPD primers. We found relatively low clonal diversities in young populations but very high clonal diversities in established populations. Therefore, the hypothesis was rejected that seedling recruitment does not occur in established populations. Moreover, we did not find large genet size asymmetries in established populations. Genet size differences can be caused by stochastic processes or by fitness related traits, such as differences in vegetative reproduction. Because vegetative propagation of ramets is dependent on ramet size, and the number of ramets and the size of each ramet determine genet size, we expected that large genets produced, on average, large ramets. However, this was not the case, suggesting that stochastic processes caused genet size differences. Genet size may also be bounded if spatial distribution of genets is affected by micro-habitat differences. For this we expected to find a clumped spatial distribution of ramets of the same genet. However, ramets of large genets were always found intermingled with ramets belonging to other genets.     

Effects of Adding Nitroprusside on Arsenic Stressed Response of Pistia stratiotes L. Under Hydroponic Conditions

Effect of nitric oxide (NO) in mitigating stress induced by arsenic (As) was assessed in Pistia stratiotes, with NO supplied as sodium nitroprusside (SNP). Plants were exposed to four treatments: control, SNP (0.1 mg L^?1), As (1.5 mg L^?1), As + SNP (1.5 and 0.1 mg L^?1), for seven days (analyses of growth, absorption of As and mineral nutrients) and for 24 h (analyses of concentration of reactive oxygen intermediates (ROIs), antioxidant capacity and photosynthesis). P. stratiotes accumulated high concentrations of As and this accumulation wasn't affected by the addition of SNP, but the tolerance index of the plant to As increased. SNP attenuated effects of As on the absorption of mineral nutrients (Ca, Fe, Mn, and Mg), but not for phosphorus, and maintained concentrations of ROIs to normal levels, probably due to the increase in antioxidant capacity. The As damaged the photosynthesis by the decrease in pigment contents and by disturbance the photochemical (loss of PSII efficiency and increases in non-photochemical quenching coefficient) and biochemical (reductions in carbon assimilation, increase in the C_i/C_a and Φ_PSII/Φ_CO2 ratios) steps. The addition of SNP restored these parameters to normal levels. Thus, NO was able to increasing the resistance of P. stratiotes to As.

Supplemental materials are available for this article. Go to the publisher's online edition of International Journal of Phytoremediation to view the supplemental file.     

High Levels of Genetic Divergence among Populations in a Weedy Fern, Pteris multifida Poir.

Abstract Intragametophytic selfing in the homosporous ferns has been viewed as an advantageous mechanism permitting colonization of distant, open habitats. However, there is little evidence for the generality of colonization through intragametophytic selfing. In this study, the genetic structure of Pteris multifida was determined using Wright's F-statistics in order to detect the occurrence of this type of colonization. A high level of genetic divergence among populations (F_ST= 0.543) was found in P. multifida. This genetic divergence seems to be caused by frequent occurrences of colonization through intragametophytic selfing.     

不同居群五柱绞股蓝叶形变异及总黄酮含量分析

以不同生境的五柱绞股蓝为材料,对4个不同来源的五柱绞股蓝的叶片性状、裂叶数进行了统计,并以芦丁为对照品,采用分光光度法对4个居群五柱绞股蓝的总黄酮含量进行了测定。结果表明,五柱绞股蓝的叶型变异较大,其复叶具有3-9裂叶型类型,以7裂叶型和5裂叶型为主。相关性统计显示,野生型五柱绞股蓝黄酮含量高,与7裂叶型极显著相关,家种型五柱绞股蓝黄酮含量低,与叶型无关,环境因子可能是影响其黄酮含量的主要因子。在引种时,7裂叶型的五柱绞股蓝可作为优选资源引用。     

Gametophyte development of Woodwardia radicans (L.) Sm.: Effect of population density and antheridiogen on sex expression

Abstract

Gametophyte development of Woorwardia radicans was studied in controlled culture conditions, as well as the effect of population density and antheridiogen on sex expression. The pattern of gametophyte development is not affected by temperature, while sex expression of gametophytes is affected by sowing density, by the presence in the culture medium of «antheridiogen» and by the nutritional conditions of gametophytes. The probable effects of antheridiogen and population density on the observed developmental pattern are considered.     

砷、钙对蜈蚣草中金属元素吸收和转运的影响

蜈蚣草是砷的超富集植物和钙质土壤的指示植物。本试验在砂培条件下,研究砷、钙对蜈蚣草吸收和转运必需金属元素K、Mg、Mn、Fe、Zn和Cu的影响。结果表明。提高营养液中的砷浓度显著降低根部Mg和Zn的吸收。但对根部其它元素的浓度没有明显影响;叶柄中的Mn和地上部的Fe浓度因介质中添加砷而显著减少。其它元素在地上部的分布不受抑制。添加砷限制Fe从地下部向地上部转运,但促进其从叶柄向羽叶中运输;另外,还显著促进Mn由叶柄向羽叶和Zn由根向羽叶的转运。提高钙处理浓度对蜈蚣草吸收Fe、Zn、Cu无显著影响,但显著限制K、Mg和Mn的吸收。Mn是研究的6种金属元素中惟一一种明显向地上部转运富集的元素。从根部到羽叶中。金属元素间的相关性增强,在根部Ca与各种金属元素都无相关性;叶柄中Ca和Fe浓度呈极显著正相关;在羽叶中,Ca与K、Mg、Mn和Zn浓度呈显著负相关。     

局部供磷对玉米根系生长、磷吸收速率的影响

玉米幼苗种子根局部供磷可明显改变根系的形态。供磷区侧根生长增加,无磷区侧极生长减少。供磷区1次、2次侧根长度与2次侧根数量明显增加;而1次侧根数量则不增加。供磷区缩小时,根系生长加快,单位根区磷吸收速率增加,但单位根重磷吸收速率的增加不很明显。磷局部供应植株主要通过供磷区根系的生长来增加磷的吸收,以满足植株对磷的需求。局部供磷植株中转运到供磷根区的光合产物明显多于无磷根区。     

Measurement of Ammonium Ions in Flowing Solution Culture and Diurnal Variation Uptake by Lolium perenne L

An existing system of flowing solution culture, in which pHand the concentration of several nutrient ions are automaticallymonitored and controlled, has been extended to include at 10 mmol N m^–3. A brief account is givenof the use of the equipment with a simulated sward of perennialryegrass (Lolium perenne L.). Uptake of measured over three successive days in June, varied with dailysolar radiation and exceeded 1000 mg N m^–2 d^–1.The uptake of showed a pattern of diurnal variation similar to the variation in solar radiation, but witha lag period for uptake of 5 h. Hourly uptake rates ranged from32 to 67 mg N m^–2h^–1 and solar radiation from 0to 2.8 MJ m^–2 h^–1. During a 24 h period, additionalmeasurements were made of K⁺ uptake and net H⁺ efflux, bothof which showed patterns of diurnal variation with lag periodsof 6 h hand 7 h, respectively. The stoichiometric ratio of thesum of and K⁺ to the net efflux of H⁺ was1.02: 1. Key words: Ion uptake, diurnal variation, Lolium perenne L.     

Effects of Low Root Temperature on Ion Uptake and Ion Translocation in Wheat

Roots of wheat seedlings (Triticum aestivum L. cv. Weibulls Starke) were cooled (+1°C) for 24 h while the shoots were kept at 25°C. The treatment induced an increased water deficit in the leaves. Fresh weight, dry weight, and the uptake and distribution of potassium and calcium were measured before and after cooling. Growth, measured both as fresh weight and dry weight increase, was reduced during the cold treatment. Afterwards (at 20°C), growth recovered to nearly pre-stress rates. Analysis of the potassium fluxes in and out of the roots by ⁸⁶Rb techniques showed that influx, and to a lesser extent efflux, were inhibited at low temperature. The result was a net potassium uptake rate of one-third that of unstressed plants. After the cooling period the potassium influx increased to the rate of control plants. The potassium efflux increased to one and one-half times the rate of unstressed wheat so that net uptake was negative. The increase in potassium efflux was explained by a higher permeability of the root cell membranes after cooling. The net uptake of calcium was reduced to one-third by root cooling. Contrary to potassium uptake, calcium uptake increased under post-stress conditions, partly due to a low efflux rate. During root cooling there was a redistribution of dry matter from the leaves down towards the lower part of the shoot. Afterwards the original distribution of dry matter was reestablished. The net flow of potassium and calcium followed a similar pattern as dry matter, suggesting a growth-regulated flow.     

长白落叶松群体遗传变异及优良家系选择的研究

以黑龙江省林口县青山林场21年生长白落叶松(Larix olgensis Henry)异地保存林为材料,分析白刀山种源优良木和劣等木群体的生长变异情况。结果发现优势木群体和劣等木群体差异不显著。树高、胸径、材积都存在丰富的变异,其中变异系数最大的是材积,其次是胸径,最小的是树高,其变异系数分别为46.24%、19.82%和12.25%;优势木群体树高、胸径、材积的变异系数分别是12.98%、20.77%和49.36%;劣等木群体树高、胸径、材积的变异系数分别是11.47%、18.79%和43.16%。同一性状树高、胸径、材积优势木群体变异高出劣等木群体变异系数分别为1.51%、1.98%和6.2%。方差分析表明家系间差异显著,选择了856、859、563、552、567、864号6个优良家系,优良木与劣等木群体各占3个;6个家系平均值分别超过优势木群体平均值和劣等木群体平均值0.017 7和0.013 6 m3。按照各自群体10%入选率,则遗传增益分别是38.74%和30.04%。