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Background and aims: Water spinach readily uptakes cadmium (Cd), posing a risk to human health. Selecting low-Cd cultivars is a promising mitigation strategy, but its extensive utilization is limited without a clear understanding of the critical plant factors determining Cd accumulation. This study aimed to elucidate the effects and interactions of the radial oxygen loss (ROL) and iron (Fe) plaque on the Cd accumulation in different water spinach cultivars and the underlying mechanisms. Methods: A pot and four hydroponic experiments using ten water spinach cultivars were conducted with different aeration, Fe supply, and Cd stress treatments. Results: The Cd accumulation of different cultivars was determined by both root uptake and root-to-shoot transport. There were 4.0-, 3.8- and 6.3-fold differences among different cultivars in ROL, Fe plaque, and shoot Cd accumulation, respectively. Rhizosphere and root Fe plaque reduced root Cd uptake and were regulated by Fe supply and ROL. Increased ROL under stagnant conditions enhanced Fe plaque and induced its redistribution along root axes. Root Cd retention through compartmentalization and chelation inhibited root-to-shoot Cd translocation. Conclusion: The Fe plaque, ROL, and root Cd retention formed an interactive system to decrease the Cd uptake and accumulation in water spinach. Low-Cd cultivars exhibited higher ROL, greater Fe plaque and more effective root Cd retention, and responded to stagnant conditions with greater ROL increases and more enhanced Fe deposition on root surfaces. This study provides new insights into the Cd accumulation mechanisms in water spinach and a theoretical basis for selecting low-Cd cultivars. [ABSTRACT FROM AUTHOR]

A novel catalyst acid-modified red mud (RM) supported by peanut shells (MRP) was synthesized by pyrolysis (700 ℃) using RM and peanut shells (PSL) for oxidative degradation of methyl orange (MO) from aqueous solution by activating peroxydisulfate (PDS). Scanning electron microscope (SEM) showed that MRP was porous and RM was well loaded on inside the pores and outer surface of the peanut shells biochar. In addition, the influence of different preparation conditions on the catalyst performance was explored. The SBET of MRP1 increased from 7.78 to 86.13 m2 g−1 and the Fe content reached 18.35% after treatment. About 96% removal ratio of MO was achieved within 80 min under the conditions of 1.0 mM PDS, 100 mg L−1 MO and 0.8 g L−1 MRP1. When MO and Cr6+ coexisted, the removal ratios of MO and Cr6+ achieved 85.98% and 76.07%, respectively. Kinetic analysis of experimental data has shown that the MO degradation reaction better fitted to the pseudo-first-order kinetics than other models such as pseudo-second-order kinetic model. Quenching experiments and electron paramagnetic resonance demonstrated that 1O2 was the main active substance to the degradation of MO in the MRP1/PDS system. 1O2 produced by different free radical reactions, which came from PDS activated by Fe2+ in MRP. The removal efficiency achieved 71% in the 5th reuse of MRP1, indicating the potential of MPR to treat MO in actual applications. Finally, this study provided new insights for the development of various functionalized RM-biochar composite materials as efficient heterogeneous catalysts for environmental remediation. [ABSTRACT FROM AUTHOR]

The feasibility of removal of chemical oxygen demand (COD) and ammonia nitrogen (NH4+–N) from landfill leachate by an electrochemical assisted HClO/Fe2+ process is demonstrated for the first time. The performance of active chlorine generation at the anode was evaluated in Na2SO4/NaCl media, and a higher amount of active chlorine was produced at greater chloride concentration and higher current density. The probe experiments confirmed the coexistence of hydroxyl radical (•OH) and Fe(IV)-oxo complex (FeIVO2+) in the HClO/Fe2+ system. The influence of initial pH, Fe2+ concentration, and applied current density on COD and NH4+–N abatement was elaborately investigated. The optimum pH was found to be 3.0, and the proper increase in Fe2+ dosage and current density resulted in higher COD removal due to the accelerated accumulation of •OH and FeIVO2+ in the bulk liquid phase, whereas, the NH4+–N oxidation was significantly affected by the applied current density because of the effective active chlorine generation at higher current but was nearly independent of Fe2+ concentration. The reaction mechanism of electrochemical assisted HClO/Fe2+ treatment of landfill leachate was finally proposed. The powerful •OH and FeIVO2+, in concomitance with active chlorine and M(•OH), were responsible for COD abatement, and active chlorine played a key role in NH4+–N oxidation. The proposed electrochemical assisted HClO/Fe2+ process is a promising alternative for the treatment of refractory landfill leachate. [ABSTRACT FROM AUTHOR]

The reclamation of mine waste deposits is often hindered by the scarcity of natural topsoil. Acid mine drainage sludge (AMDS), as a mass-produced waste in metalliferous mines, is a potential topsoil substitute but had not been validated. In this study, a pot experiment with three plant species was conducted to evaluate the capacity of AMDS to support plant growth, buffer acidification, and immobilize heavy metal(loid)s when reclaiming mine waste rocks. Chemical fertilizer and compost chicken manure were applied to AMDS at different rates to explore their effects on plant growth and the physicochemical properties of AMDS. Results showed that all the plants could survive in AMDS even without fertilization. The contents of heavy metal(loid)s in rhizosphere remained almost unchanged over the experimental period, indicating low leachability of revegetated AMDS. Fertilizers enhanced macronutrients and soil enzyme activities, leading to significant increases in plant biomass. However, owing to manure composting and low richness and diversity of the bacterial community in AMDS, the NH4+-N and bioavailable phosphorus contents were extremely low. Bermuda grass was a suitable pioneer species for reclamation for its better adaptability to nutrient deficiency and heavy metal(loid) stress. Overall, AMDS is a viable soil substitute for mine reclamation due to its capability to support plant growth and environmental safety. [ABSTRACT FROM AUTHOR]

One of the main challenges of electrochemical Fenton-based processes is the treatment of organic pollutants at near-neutral pH. As a potential approach to this problem, this work addresses the use of a low content of soluble chelated metal catalyst, formed between Fe(III) and ethylenediamine-N,N'-disuccinic (EDDS) acid (1:1), to degrade the herbicide triclopyr in 0.050 M Na2SO4 solutions at pH 7.0 by photoelectro-Fenton with UVA light or sunlight (PEF and SPEF, respectively). Comparison with electro-Fenton treatments revealed the crucial role of the photo-Fenton-like reaction, since this promoted the production of soluble Fe(II) that enhanced the pesticide removal. Hydroxyl radicals formed at the anode surface and in the bulk were the main oxidants. A boron-doped diamond (BDD) anode yielded a greater mineralization than an IrO2-based one, at the expense of reduced cost-effectiveness. The effect of catalyst concentration and current density on the performance of PEF with BDD was examined. The PEF trials in 0.25 mM Na2SO4 + 0.35 mM NaCl medium showed a large influence of generated active chlorine as oxidant, being IrO2 more suitable than RuO2 and BDD. In SPEF with BDD, the higher light intensity from solar photons accelerated the removal of the catalyst and triclopyr, with small effect on mineralization. A plausible route for the herbicide degradation by Fe(III)–EDDS-catalyzed PEF and SPEF is finally proposed based on detected byproducts: three heteroaromatic and four linear N-aliphatic compounds, formamide, and tartronic and oxamic acids. [ABSTRACT FROM AUTHOR]

Background and aims: Large areas of paddy fields have been contaminated by cadmium (Cd) in both China and worldwide, resulting in excessive Cd accumulation in rice grains. Here, we investigated the effects of cultivars, water regimes, and growth stages on Cd accumulation in rice with different radial oxygen loss (ROL). Methods: Two groups of experiments were conducted: pot trials with soil-added Cd and solution-added agar using 20 rice cultivars and a rhizobag trial with Cd-contaminated soil and pot trial with solution-added agar under flooded and non-flooded water regimes with three growth stages and two cultivars. Results: Different rice cultivars exhibited different porosity, Cd tolerance, and Cd accumulation in grains, which were significantly correlated with ROL. Cd concentration in shoots was significantly lower under the flooded (0.13–1.01, mean 0.56 mg kg−1) than non-flooded regime (0.68–1.39, mean 0.97 mg kg−1). The low Cd-accumulating cultivar showed higher rates of ROL, higher Cd combined with Fe plaque formation, and lower Cd bioavailability in the rhizosphere soil than the high-Cd accumulating cultivar. Conclusions: Rice cultivars grown under flooded regimes effectively reduced Cd accumulation in edible parts, and the later stage was crucial for reducing Cd accumulation. Low Cd-accumulating cultivars generally exhibited a higher ability to reduce Cd bioavailability in the rhizosphere soil. [ABSTRACT FROM AUTHOR]

Background and aims: Rice grains contaminated by mercury (Hg) and methylmercury (MeHg) pose risks to human health. This study evaluated the relative importance of genotype, environment and genotype-environment interactions on the accumulation of total Hg (THg) and MeHg in brown rice.Methods: A pot trial with four rice genotypes and 10 Hg-contaminated paddy soils was conducted under greenhouse conditions. The effects of genotype, environment and genotype-environment interactions on brown rice THg and MeHg accumulation were assessed by an Additive Main Effects and Multiplicative Interaction (AMMI) model.Results: THg and MeHg concentrations in brown rice ranged from 20.5 to 75.5 μg kg−1 and 2.24 to 54.7 μg kg−1, respectively. The AMMI model indicated that genotype explained 41.1 and 19.6%, environment described 40.6 and 55.8%, and the genotype-environment interaction explained 11.9 and 20.0% of the variation in brown rice THg and MeHg levels, respectively. Brown rice THg positively correlated with water-soluble Hg and total potassium, but negatively correlated with total sulphur, iron, total organic carbon and nickel in soils. Brown rice MeHg negatively correlated with soil pH and selenium.Conclusion: THg accumulation in brown rice was mainly affected by both genotype and environment, whereas MeHg accumulation was largely determined by environment. [ABSTRACT FROM AUTHOR]

Large areas of paddy fields in mining areas in south China have been contaminated by mixed Cd and As. To test the possibility of using organic manure (OM) as a method of reducing Cd and As accumulation in brown rice and increase the grain yield in such paddy fields, two rice cultivars [Jianyou G2 (JY) and Fengyousimiao (FY)] and three amounts of OM (0, 0.5, 1.5 kg/m) were examined in three Cd-As-contaminated paddy fields (Fogang, Dabaoshan, Fankou) in Guangdong Province. The results show that the application of OM can effectively increase the grain yield and reduce Cd. However, the As concentration was found to increase in brown rice, especially when high levels of OM were used. The addition of OM increased the soil pH and organic matter content in the soils and enhanced the activities of superoxide dismutase (SOD) and catalase (CAT) in plant tissues. Our results suggest that OM can be used as an amendment to effectively decrease Cd accumulation in brown rice in Cd-contaminated paddy fields. However, it is necessary to consider the negative effects of OM amendments when adding OM to As-contaminated paddy fields. [ABSTRACT FROM AUTHOR]

Paddy soils and rice ( Oryza sativa L.) contaminated by mixed heavy metals have given rise to great concern. Field experiments were conducted over two cultivation seasons to study the effects of steel slag (SS), fly ash (FA), limestone (LS), bioorganic fertilizer (BF), and the combination of SS and BF (SSBF) on rice grain yield, Cd, Pb, and Zn and nutrient accumulation in brown rice, bioavailability of Cd, Pb, and Zn in soil as well as soil properties (pH and catalase), at two acidic paddy fields contaminated with mixed heavy metals (Cd, Pb, and Zn). Compared to the controls, SS, LS, and SSBF at both low and high additions significantly elevated soil pH over both cultivation seasons. The high treatments of SS and SSBF markedly increased grain yields, the accumulation of P and Ca in brown rice and soil catalase activities in the first cultivation season. The most striking result was from SS application (4.0 t ha) that consistently and significantly reduced the soil bioavailability of Cd, Pb, and Zn by 38.5-91.2 % and the concentrations of Cd and Pb in brown rice by 20.9-50.9 % in the two soils over both cultivation seasons. LS addition (4.0 t ha) also markedly reduced the bioavailable Cd, Pb, and Zn in soil and the Cd concentrations in brown rice. BF remobilized soil Cd and Pb leading to more accumulation of these metals in brown rice. The results showed that steel slag was most effective in the remediation of acidic paddy soils contaminated with mixed heavy metals. [ABSTRACT FROM AUTHOR]

Background and aims: Rice contaminated by mercury [Hg, especially methylmercury (MeHg)] has given rise to great concern in recent years. This study investigated variations in ecophysiological features (anatomy, organic acid secretions, Fe plaque formation) of rice roots and their effects on the uptake and accumulation of total mercury (THg) and MeHg by rice plants. Methods: The development of apoplastic barriers in roots of four rice cultivars was observed by a hydroponic experiment while the concentrations of five organic acids, Fe and THg in Fe plaque were determined using a rhizobag trial with different Hg treatments. Results: Cultivars with low Hg accumulation tended to develop strong apoplastic barriers in endodermis, secrete less organic acids and form more Fe plaque on root surfaces and in rhizosphere. Fe concentrations were positively correlated with THg concentrations in rhizosphere's Fe plaque (R = 0.60, P < 0.01), whereas the latter was negatively correlated with bioavailable Hg concentrations in rhizosphere (R = 0.40, P < 0.01). Conclusions: Organic acids and Fe plaque formation of rice roots play important roles in Hg uptake and accumulation. The development of apoplastic barriers in root restricts Hg uptake but the significance of suberin deposition on Hg uptake needs further investigations. [ABSTRACT FROM AUTHOR]

Background and aims: Water spinach is a common leafy vegetable in Asia, with a strong ability to accumulate cadmium (Cd) in its edible parts. The aims of this study were to investigate the effects of cultivar variation and water management on Cd accumulation in this plant. Methods: Three experiments were conducted: a soil pot trial with 32 cultivars, a rhizobox trial with 4 cultivars under flooded and non-flooded conditions and an uptake kinetics trial with 2 cultivars. Results: There were significant differences in Cd accumulation between the different cultivars, and Cd concentrations in shoots were significantly lower in the flooded (0.25-1.4, mean 0.90 mg kg DW) than in the non-flooded (1.9-4.7, 3.2 mg kg) treatments. Cultivars with a low Cd accumulation had a lower Cd bioavailability and mobility in the rhizosphere soil, higher Cd combined with Fe plaque on roots, lower Cd uptake capacity by roots, and lower Cd transfer factors than those with a high Cd accumulation. Conclusions: Water spinach grown under anaerobic conditions effectively reduces Cd accumulation in edible parts. Low Cd-accumulating cultivars tend to possess a high ability to reduce Cd bioavailability in rhizosphere soil, as well as decrease Cd uptake, and translocation from root to shoot. [ABSTRACT FROM AUTHOR]

Constructed wetlands used to clean up toxic metals such as lead (Pb) from contaminated wastewater are considered as an effective and low-cost technology. The effect of Pb on the biomass, tolerance, soluble protein, and antioxidant enzymes in 18 candidate wetland plant species grown in soils without (control) and spiked with 900 and 1800 mg Pb kg was studied in a pot trial. Our pot experiment showed that the biomass, tolerance, and leaf protein contents decreased with increasing concentrations of Pb in soil. There were significant differences between the plants in their Pb tolerance indices (29-82 % in the 900 mg Pb kg amended soil) and also Pb uptake (13-749 mg kg in shoots and 1112-4891 mg kg in roots, in the same treatments). Activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves of most of the plants increased with increasing level of soil Pb concentration. Conversely, catalase (CAT) activity in leaves declined when plants were subjected to Pb stress. Lead accumulation by the 18 wetland plant species screened was strongly dependent on the species and Pb concentrations in the soil. However, Pb translocation from root to shoot was generally low in all species. Increases in SOD and POD activities suggest that the antioxidant system may play an important role in alleviating Pb toxicity in wetland plants. The data obtained should help in future species selection for the use in designing wetlands in Pb-contaminated environments. [ABSTRACT FROM AUTHOR]

Background and Aims: Mercury (Hg) pollution in paddy fields and rice has aroused great concern in recent years. This study investigated the dynamic changes of radial oxygen loss (ROL) and Fe plaque formation on roots, and their effects on Hg accumulation in rice plants. Methods: A rhizobag experiment was conducted to study temporal variations and correlations between ROL (amounts and rates), Fe plaque formation, total Hg (THg) and methylmercury (MeHg) in plant tissues and in plaque of four rice cultivars during six growth stages. Results: ROL amounts and Fe plaque formation increased from tillering to reproductive stages, then ROL amounts gradually decreased until maturation stage, whereas Fe plaque remained relatively stable. ROL rates continued to decline during the entire growth period. Both ROL amounts and Fe concentrations in plaque were positively correlated with THg concentrations in the plaque, whereas negatively correlated with THg in straw and brown rice. However, there were no significant relationships between ROL, Fe in plaque and MeHg in plaque and in plant tissues. Conclusions: ROL has great effects on THg but not MeHg accumulation in rice plants. Rice cultivars with higher ROLs tend to have a greater ability to reduce THg accumulation in brown rice. [ABSTRACT FROM AUTHOR]

Background and Aims: Metal (e.g. Cd and Pb) pollution in agricultural soils and crops have aroused considerable attention in recent years. This study aimed to evaluate the effects of ROL and Fe plaque on Cd and Pb accumulation and distribution in the rice plant. Methods: A rhizobag experiment was employed to investigate the correlations among radial oxygen loss (ROL), Fe plaque formation and uptake and distribution of Cd and Pb in 25 rice cultivars. Results: Large differences between the cultivars were found in rates of ROL (1.55 to 6.88 mmol O kg root d.w. h), Fe plaque formation (Fe: 6,117-48,167 mg kg; Mn: 127-1,089 mg kg), heavy metals in shoot (Cd: 0.13-0.35 mg kg; Pb: 4.8-8.1 mg kg) and root tissues (Cd: 1.1-3.5 mg kg; Pb: 45-199 mg kg), and in Fe plaque (Cd: 0.54-2.6 mg kg; Pb: 102-708 mg kg). Rates of ROL were positively correlated with Fe plaque formation and metal deposition on root surfaces, but negatively correlated with metal transfer factors of root/plaque and distributions in shoot and root tissues. Conclusions: ROL-induced Fe plaque promotes metal deposition on to root surfaces, leading to a limitation of Cd and Pb transfer and distribution in rice plant tissues. [ABSTRACT FROM AUTHOR]

Background and aims: Wetland plants have been widely used in constructed wetlands for the clean-up of metal-contaminated waters. This study investigated the relationship between rate of radial oxygen loss (ROL), root porosity, Zn uptake and tolerance, Fe plaque formation in wetland plants. Methods: A hydroponic experiment and a pot trial with Zn-contaminated soil were conducted to apply different Zn level treatments to various emergent wetland plants. Results: Significant differences were found between plants in their root porosities, rates of ROL, Zn uptake and Zn tolerance indices in the hydroponic experiment, and concentrations of Fe and Mn on roots and in the rhizosphere in the pot trial. There were significant positive correlations between root porosities, ROL rates, Zn tolerance, Zn, Fe and Mn concentrations on roots and in the rhizosphere. Wetland plants with higher root porosities and ROL tended to have more Fe plaque, higher Zn concentrations on roots and in their rhizospheres, and were more tolerant of Zn toxicity. Conclusions: Our results suggest that ROL and root porosity play very important roles in Fe plaque formation, Zn uptake and tolerance, and are useful criteria for selecting wetland plants for the phytoremediation of Zn-contaminated waters and soils/sediments. [ABSTRACT FROM AUTHOR]

Temporal variations and correlations between radial oxygen loss (ROL), iron (Fe) plaque formation, cadmium (Cd) and arsenic (As) accumulation were investigated in two rice cultivars at four different growth stages based upon soil pot and deoxygenated solution experiments. The results showed that there were significant differences in ROL (1.1-16 μmol O plant h), Fe plaque formation (4,097-36,056 mg kg), Cd and As in root tissues (Cd 77-162 mg kg; As 49-199 mg kg) and Fe plaque (Cd 0.4-24 mg kg; As 185-1,396 mg kg) between these growth stages. ROL and Fe plaque increased dramatically from tillering to ear emergence stages and then were much reduced at the grain-filling stage. Furthermore, significantly positive correlations were detected between ROL and concentrations of Fe, Cd and As in Fe plaque. Our study indicates that increased Fe plaque forms on rice roots at the ear emergence stage due to the increased ROL. This stage could therefore be an important period to limit the transfer and distribution of Cd and As in rice plants when growing in soils contaminated with these toxic elements. [ABSTRACT FROM AUTHOR]

Greenhouse experiment was conducted to examine effects of arsenic (As) on iron plaque formation, radial oxygen loss, As accumulation, and speciation in rice. Three genotypes were grown in soil with three different concentrations of As. The stress of As caused a slight increase of iron plaque formation ( P > 0.05) and a decrease in the rates of radial oxygen loss (ROL; P < 0.01). The results of As speciation showed that the percentages of DMA increased from 19–28 % to 53–58 %, while the percentages of inorganic As decreased from 53–58 % to 36–42 % with the increasing soil As concentrations, indicating a strong environmental influence on As species in rice grain. The present study showed that elevated soil As may induce As toxicity towards rice plants, leading to the decrease of ROL; environmental factors could influence As methylation or As species transportation. Our study provided useful information on As tolerance and accumulation in rice which may contribute to reducing the health risk posed by As contamination in rice. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Concentrations of six heavy metals (Cu, Ni, Zn, Cd, Cr, and Pb) in sediments and fine roots, thick roots, branches, and leaves of six mangrove plant species collected from the Futian mangrove forest, South China were measured. The results show that both the sediments and plants in Futian mangrove ecosystem are moderately contaminated by heavy metals, with the main contaminants being Zn and Cu. All investigated metals showed very similar distribution patterns in the sediments, implying that they had the same anthropogenic source(s). High accumulations of the heavy metals were observed in the root tissues, especially the fine roots, and much lower concentrations in the other organs. This indicates that the roots strongly immobilize the heavy metals and (hence) that mangrove plants possess mechanisms that limit the upward transport of heavy metals and exclude them from sensitive tissues. The growth performance of propagules and 6-month-old seedlings of Bruguiera gymnorhiza in the presence of contaminating Cu and Cd was also examined. The results show that this plant is not sufficiently sensitive to heavy metals after its propagule stage for its regeneration and growth to be significantly affected by heavy metal contamination in the Futian mangrove ecosystem. However, older mangrove seedlings appeared to be more metal-tolerant than the younger seedlings due to their more efficient exclusion mechanism. Thus, the effects of metal contamination on young seedlings should be assessed when evaluating the risks posed by heavy metals in an ecosystem. [ABSTRACT FROM AUTHOR]

Purpose: Mangrove wetlands have experienced significant contaminant input such as copper (Cu), aggravated by rapid urban development. This study aimed to investigate the possible function of root permeability in metal detoxification. Methods: Pot trials were conducted to evaluate the responses of root permeability in relation to metal (Cu) exposure in seedlings of two mangroves: Bruguiera gymnorrhiza and Rhizophora stylosa. Results: Copper inhibited plant growth and root permeability of the two species significantly (due to decreases in root porosity, thickening of exodermis and increases in lignification), leading to a significant reduction in radial oxygen loss (ROL). A negative correlation between soil Cu and ROL from root tip was also observed. The observed metal uptake by excised roots further indicated that increased lignification would directly prevent excessive Cu from further entering into the roots. Conclusions: In summary, the two mangroves reacted to Cu by producing an impermeable barrier in roots. Such an inducible barrier to ROL is likely to be an adaptive strategy against Cu toxicity. This study reveals new evidence of a structural adaptive strategy for metal tolerance by mangrove plants. [ABSTRACT FROM AUTHOR]

This paper briefly reviews the progress in studies of wetland plants in terms of heavy metal pollution. The current research mainly includes the following areas: (1) metal uptake, translocation, and distributions in wetland plants and toxicological effects on wetland plants, (2) radial oxygen loss (ROL) of wetland plants and its effects on metal mobility in rhizosphere soils, (3) constitutional metal tolerance in wetland plants, and (4) mechanisms of metal tolerance by wetland plants. Although a number of accomplishments have been achieved, many issues still remain unanswered. The future research effort is likely to focus on the ROL of wetland plants affecting metal speciation and bioavailability in rhizosphere soils, and the development of rhizosphere management technologies to facilitate and improve practical applications of phytoremediation of metal-polluted soils. [ABSTRACT FROM AUTHOR]

In this article, a method for quantitative determination of phytochelatins (PC n being the classic example) and other thiol-containing compounds in mixed standard solution and plant tissues is presented. Thiols were converted to fluorescent derivatives by precolumn derivatization with monobromobimane. The results showed that PC n and other thiol-containing compounds in standard mixed solutions were rapidly separated within 15 min by using a ACN 0.1% trifluoroacetic acid binary gradient elution. Glutathione was representatively selected to test the precision of this method. The calibration curve was linear in the range of 1.25–160 ng μl−1 (regression coefficient r2=0.9999). It was confirmed that this method was rapid, simple, highly sensitive, stable, and had the property of simultaneous determination of PC n and other thiol-containing compounds. This method was applied to determine PC n and other thiol-containing compounds in a Cd hyperaccumulator Sedum alfredii in response to Cd. It was found that no PC n was detected in any tissue at any Cd treatment, suggesting that Cd hyperaccumulation and detoxification in this plant is not based on PC synthesis. [ABSTRACT FROM AUTHOR]