Great Potential For Phytoremediation Research Articles

Copper and zinc accumulation, distribution, and tolerance in Pistia stratiotes L.; revealing the role of root caps

Pollution by potentially toxic trace metals, such as copper or zinc, is global. Both Cu and Zn are essential microelements, which in higher concentrations become toxic. The aquatic plant Pistiastratiotes(L. has great potential for phytoremediation. Also, it has an unusually large and easily detachable root cap, which makes it a suitable model for studying the potential role of the root cap in metal uptake. Plant response to environmentally relevant concentrations of Cu (0.1, 0.3, and 1μM) and Zn (0.3, 1, and 3μM) was investigated with the aim of studying their interaction and distribution at the root tissue level as well as revealing their tolerance mechanisms. Changes in the root anatomy and plant ionome were determined using light and fluorescence microscopy, ICP-MS, and μXRF imaging. Alterations in photosynthetic activity caused by Cu or Zn excesses were monitored by direct imaging of fast chlorophyll fluorescence kinetics (OJIP). Fe and Mn were preferentially localized in the root cap, while Ca, Cu, Ni, and Zn were mainly in the root tip regardless of the Cu/Zn treatment. Translocation of Cu and Zn to the leaves increased with higher doses, however the translocation factor was the lowest in the highest treatments. Measurements of photosynthetic parameters showed a higher susceptibility of electron transport flux from QAto QBunder increasing Cu than Zn supply. This, along with our findings regarding the root anatomy and the differences in Ca accumulation and distribution, led to the conclusion thatP. stratiotesis more effective for Zn remediation than Cu.

Crescimento inicial de mudas de zínia em substrato com diferentes proporções de biossólido

Abstract Zinnia (Zinnia elegans Jacq.) is a widely cultivated species and used as an ornamental plant in the world flower market. Although it has great potential for phytoremediation and compounds with anti-infective and antioxidant activities there are few studies that address the process of production of its seedlings especially using substrates from organic waste. This study aimed to evaluate the potential of biosolid as a substrate component in the initial growth of Zinnia elegans seedlings. The seedlings were produced in nursery conditions with 50% light control. The experimental design was entirely randomized. There were six treatments, four repetitions and five plants per plot. The treatments consisted of substrates resulting from the mixture of subsoil (SS) and biosolid (BIO) in different proportions: 100% SS (control); 80% SS + 20% BIO; 60% SS + 40% BIO; 40% SS + 60% BIO; 20% SS + 80% BIO; T6 100% BIO. The morphological and quality characteristics of the seedlings were evaluated. Polynomial regression analysis and Pearson correlation coefficient were performed. Quadratic regression fitting was observed for plant height, stem diameter, leaf area, total chlorophyll, and shoot and root dry mass, as well as total dry mass. The shoot height/stem diameter ratio was the characteristic that correlated least with the others, being observed a positive correlation only with plant height. The use of biosolid in the proportion of 60% in the substrate composition proved to be efficient for the initial growth of seedlings as it showed the best responses for most morphological and quality characteristics of the seedlings.

Remediation of arsenic-contaminated paddy soil by intercropping aquatic vegetables and rice

Soil contamination by arsenic (As) is an important environmental issue globally. Intercropping of hyperaccumulators with main crop is typically applied for remediation of As-contaminated soil. Most hyperaccumulators are wild plants with small biomass and slow growth rates. Thus, remediation is slow. Here, we propose an effective intercropping system for remediation of As-contaminated paddy soil. Four treatments—intercropping with water spinach (Ipomoea aquatica Forsk) (T1), water celery (Oenanthe javanica (Blume) DC.) (T2), or Guangdong white arrowhead (Sagittaria sagittifolia L. var) (T3), with rice (Oryza sativa L.) monoculture (control, CK)—were used. Compared with the CK, grain yield per plant of rice under T1 and T2 increased by 58.13% and 10.48%, respectively, but decreased by 46.90% in T3. As concentration, bioaccumulation factor, and translocation factor in brown rice were significantly lower in the intercropping treatments than in CK. As removal by water spinach was 7.04 and 1.47 times that by water celery and arrowhead, respectively. The pH of paddy soil was significantly higher in all treatments than in CK, and iron plaque on rice roots under T1 and T2 decreased significantly but increased significantly under T3 compared with that of CK. Rice intercropped with water spinach had the best remediation effect. Novelty Statement: We believe that the following highlights of this manuscript will make it interesting to general readers of this journal. First, in recent years, many articles about intercropping system for the remediation of soil heavy metal pollution focus on dry land, and few studies have focused on paddy soil. The present study was on arsenic-contaminated paddy soil remediation. Second, water spinach, water celery, and arrowhead have great potential for phytoremediation. Studies have shown that these three aquatic vegetables play a role in the removal of certain pollutants, such as heavy metals. Moreover, when intercropped with rice, they can effectively increase rice yield and reduce rice diseases and insect pests. However, studies on remediation of arsenic-contaminated soil by intercropping aquatic vegetables and rice have not been reported. We propose here a rice-aquatic vegetables (water spinach, water celery and arrowhead) intercropping pattern for remediation of arsenic in soil. Third, according to the arsenic concentration and removal rate, we used a bioaccumulation factor, translocation factor, and arsenic removal per unit area of plants for the quantitative evaluation of the remediation effects of the intercropping systems. We found that the intercropping of rice and water spinach could be used to remediate arsenic-contaminated soil. Moreover, the extraction contents of arsenic using intercropping with water spinach was higher than that achieved in a previous study that applied intercropping with the arsenic hyperaccumulator Pteris vittata over the same growth time. This study provides a reference for realizing both remediation and increased production in arsenic-contaminated soil and for promoting sustainable development of agriculture.

Pontederia cordata, an ornamental aquatic macrophyte with great potential in phytoremediation of heavy-metal-contaminated wetlands

Pontederia cordata can tolerate heavy metal toxicity and possesses great potential for phytoremediation of heavy-metal-contaminated wetlands, yet how it copes with heavy metal stress has still not been determined. Hydroponic experiments were used to assess the effects of various levels of Cd2+ on the photosynthesis and activity of redox-regulatory systems in the plant leaves, and we also sought to elucidate the tolerance mechanism of the plant to Cd2+ by investigating Cd2+ enrichment characteristics and chemical forms. The plant can manage a low cadmium concentration (≤0.04mM) with relatively stable biomass and photosynthetic performance. Cd2+ at the highest concentration (0.44mM) decreased superoxide dismutase and peroxidase activities by 37.17% and 93.29%, respectively. Similar trends were demonstrated in the contents of ascorbic acid, carotenoids, lutein, glutathione, and non-protein thiol, as well as phytochelation in the leaves, exacerbating membrane peroxidation despite the significantly increased catalase activity observed. Moreover, the highest Cd2+ concentration disturbed the biosynthesis of chlorophyll precursors in the leaves, reduced chlorophyll a and b, as well as total chlorophyll contents by 60.47%, 67.47%, and 68.12%, respectively, which inhibited photosynthesis, leading to a decline in biomass. Compared with maximum quantum efficiency (Fv/Fm) and the potential activity (Fv/Fo) of photosystem II, the performance index for energy conservation from photons absorbed by PSII to the reduction of intersystem electron acceptors (PIabs), and of PSI end acceptors (PItotal), can indicate Cd2+ toxicity to the photosynthetic apparatus in the leaves. 49.95%-76.90% of the Cd2+ was sequestered in the plant roots, restraining translocation from roots to shoots, which is considered a tolerance mechanism, probably resulting from disturbed transpiration in leaves and increased Cd2+ content with low activity. Pontederia cordata is a candidate plant for phytoremediation of heavy-metal -contaminated wetlands.

Arbuscular mycorrhiza and plant chromium tolerance

Arbuscular mycorrhizal (AM) fungi are ubiquitous soil fungi that form symbiotic associations with most terrestrial plants. The growth and functions of AM fungi depend on carbohydrates supplied by the plants, in return, the fungi assist the plants to acquire mineral nutrients (e.g., phosphorus) from soil. The AM symbiosis also improves plant survival in various unfavorable environments, such as metal (loid) contaminated soil. It has been well demonstrated that AM symbiosis improved plant adaptation to Cr contamination, which would have a great potential in phytoremediation and ecological restoration of Cr contaminated soils. In this paper, we have reviewed the role of AM fungi in alleviation of Cr phytotoxicity and associated factors influencing plant Cr tolerance. AM symbiosis improves plant Cr tolerance through its direct roles in Cr stabilization and transformation and indirect roles via AM symbiosis mediated nutrient acquisition and physiological regulation. Future research on physiological and molecular mechanisms underlying Cr behavior and detoxification in AM symbiosis, as well as potential use of AM fungi in ecological restoration and agriculture production in Cr contaminated soils were also proposed.

Pilot testing of a bioremediation system for water and soils contaminated with heavy metals: vegetable depuration module

We present a novel constructed wetland called a vegetable depuration module (VDM) as a pilot test of a bioremediation system (BS) for decontaminating water and soil polluted with heavy metals. The VDM consisted of a pool filled with stones of different granulometry and a substrate top layer composed of a mixture of soil and volcanic ash (50:50, v/v) supplemented with 350 ppm Zn. The BS of sunflower plants colonized by the arbuscular mycorrhizal fungus Rhizophagus intraradices was planted in the VDM. Initially, the substrate registered high concentrations of Zn, Cr, Mn, Cu, and Sr, and had Eh > +500 mV and pH 8.4. Irrigation with a Cu solution by vertical flow was carried out. After 3 months, bioaccumulation factors ranged from 1.00 to 8.90, and translocation rates were >1 for Sr and Cu. Total metals extracted by the BS and percolation were 31%, 34%, 50%, 45%, and 57% for Zn, Cu, Mn, Cr, and Sr, respectively. Only the BS was capable of extracting 94% of Cu and 38% of Zn. VDM allowed us to calibrate the extractive performance of the studied elements in BS. This biotechnological development holds great potential for phytoremediation of polluted areas.

Subcellular distribution of cadmium in a novel potential aquatic hyperaccumulator – Microsorum pteropus

Microsorum pteropus is a novel potential Cd (cadmium) aquatic hyperaccumulator. In the present study, hydroponic experiments were conducted to assess the accumulation and subcellular distribution of Cd in the root, stem and leaf of M.pteropus. SEM (scanning electron microscopy) - EDX (energy dispersive X-ray fluorescence spectrometer) and TEM (transmission electron microscopy) were used to observe the ultrastructure of different tissues under 500 μM Cd exposure. After exposure to 500 μM Cd for 7 days, the root, stem and leaf of M.pteropus can accumulate to be > 400 mg/kg Cd in dry mass with no significant influence on the growth. In the root and leaf of M.pteropus, the Cd was more likely to store in the cell wall fraction. However, Cd in the stem was mainly stored in both the cell wall fraction and the cytoplasm fraction. Under SEM observation and EDX detection, 1) Cd was found to be sequestrated in the epidermis or chelated in the root cells, 2) no significant deposit spots were observed in the stem, 3) Cd was found in the trichome of the leaf, and the sporangium was not damaged. TEM observations revealed 1) possible Cd precipitations in the root cell and 2) no significant ultrastructure variation in the stem, and 3) the chloroplast retained its structure and was not affected by the Cd. M.pteropus showed great capacity for Cd accumulation without influencing growth. In addition, the ultrastructure of all the tissues was not damaged by the Cd. M.pteropus showed a great potential in phytoremediation in heavy metal polluted water solutions, and may provide new directions for the study of resistance mechanisms of aquatic hyperaccumulators.

Comparative transcriptome combined with morpho‐physiological analyses revealed key factors for differential cadmium accumulation in two contrasting sweet sorghum genotypes

SummaryCadmium (Cd) is a widespread soil contaminant threatening human health. As an ideal energy plant, sweet sorghum (Sorghum bicolor (L.) Moench) has great potential in phytoremediation of Cd‐polluted soils, although the molecular mechanisms are largely unknown. In this study, key factors responsible for differential Cd accumulation between two contrasting sweet sorghum genotypes (high‐Cd accumulation one H18, and low‐Cd accumulation one L69) were investigated. H18 exhibited a much higher ability of Cd uptake and translocation than L69. Furthermore, Cd uptake through symplasmic pathway and Cd concentrations in xylem sap were both higher in H18 than those in L69. Root anatomy observation found the endodermal apoplasmic barriers were much stronger in L69, which may restrict the Cd loading into xylem. The molecular mechanisms underlying these morpho‐physiological traits were further dissected by comparative transcriptome analysis. Many genes involved in cell wall modification and heavy metal transport were found to be Cd‐responsive DEGs and/or DEGs between these two genotypes. KEGG pathway analysis found phenylpropanoid biosynthesis pathway was over‐represented, indicating this pathway may play important roles in differential Cd accumulation between two genotypes. Based on these results, a schematic representation of main processes involved in differential Cd uptake and translocation in H18 and L69 is proposed, which suggests that higher Cd accumulation in H18 depends on a multilevel coordination of efficient Cd uptake and transport, including efficient root uptake and xylem loading, less root cell wall binding, and weaker endodermal apoplasmic barriers.

Assessment of the phytoremediation potential and an adaptive response of Festuca rubra L. sown on fly ash deposits: Native grass has a pivotal role in ecorestoration management

Abstract Fly ash (FA) is a coal combustion by-product of thermal power plants, and has been recognized as a great environmental and health hazard worldwide. The establisment of a permanent green cover on fly ash deposits is essential and can be achieved by sowing the native plant species that should be crucial for stability and resilience of an ecosystem. Improved understanding of species’ response to unfavorable properties of fly ash provides key insight into the decision about ecorestoration practice and management. Therefore, long-term research based on the assessment of the phytoremediation potential and adaptive response of Festuca rubra L. (red fescue) sown on the fly ash deposits at the thermoelectric power plant ‘Nikola Tesla-A’ in Obrenovac (Serbia) was the main concern. Field research was carried out on the passive FA lagoons (L3—the lagoons 3 years old and L2—the lagoons 11 years old) and in the Botanical Garden Jevremovac in Belgrade (CS—control site). The physico-chemical properties of soil and fly ash were determined by using standard soil analyses. The element concentrations in soils, fly ash and plants were determined by using ICP-OES. Chlorophyll a fluorescence parameters were measured by using the Plant Stress Meter. Pigments, phenolics and malonyldialdehide contents (MDA) in leaves were measured spectrophotometrically and the total antioxidant capacity in plant leaves was determined by using DPPH free radical. Site-dependent variations were observed for all the parameters examined. FA contains alkaline pH, high electrical conductivity (EC) and low total nitrogen (N) coupled with toxic elements i.e. As and B as well as deficiency of Mn and Zn. Improvement of the physico-chemical characteristics of FA over time is reflected in the increased values of higroscopic water (HW), silt, clay, the amount of adsorbed bases (S), total adsorption capacity (T) and the reduced concentrations of total and available As, B, Cu, Zn and Mn (except available As content) indicating favorable fly ash conditions. F. rubra is an excluder plant, it retains a larger content of As, Cu, Mn and Zn in roots than in leaves and with extensive root system it can provide good fly ash stabilization, i.e. this species has a great potential in phytoremediation of FA. Furthermore, results show that F. rubra sown on the FA deposits has a high amount of MDA and reduced values of chlorophyll a fluorescence parameters (Fm, Fv, Fv/Fm, Fm/Fo), chlorophylls (Chl a, Chl a + b) and total carotenoids (Tot Carot) indicating high oxidative stress and lower efficiency of photosynthesis. However, in spite of toxic concentrations of As and B and low content of Cu, Mn and Zn in the leaves, this species has high potential to activate adaptive mechanisms, such as increased biosynthesis of anthocyanins, phenolics, ascorbic acid and total radical scavenging activity. Taken together, F. rubra possesses high adaptive capacity to perform functional ecorestoration on fly ash deposits. These findings indicate that F. rubra can be identified as a vital element for large-scale reclamation purpose.

Nickel-hyperaccumulating species of Phyllanthus (Phyllanthaceae) from the Philippines

Botanical exploration on ultramafic sites in Palawan, Surigao and Zambales has resulted in the discovery of a new hypernickelophore species (nickel (Ni) concentration >1%) of Phyllanthus (Phyllanthaceae). This paper reports in detail the Ni uptake of populations of P. erythrotrichus in Candelaria, Masinloc and Santa Cruz, Zambales, and confirms the status of P. securinegoides in Taganito, Surigao del Norte, which had been analysed only through herbarium specimens, and these were compared with a known hypernickelophore, P. balgooyi, which was collected in Narra and Puerto Princesa, Palawan. Nickel content of the dried leaves, stems and root tissues was quantified using atomic absorption spectrophotometer. P. erythrotrichus and P. securinegoides both had more than 10 000 µg g–1 Ni in the leaves, whereas the roots had 1195 µg g–1 and 4636 µg g–1. P. balgooyi accumulated 6319 µg g–1 of Ni in the leaves, whereas the roots had a higher Ni concentration of up to 8116 µg g–1, respectively. All three species had values of translocation factor and enrichment factor of >1.0, implying that all species have great potential in phytoremediation, specifically, phytoextraction of Ni. These three species of Phyllanthus are prominent in ultramafic scrub communities and, hence, should be used in ecological restoration of mined-out Ni lateritic areas. The implications of the unique adaptation of these species are also discussed in relation to a conservation strategy for their natural populations.

Effectiveness of Phytoremediation Technologies to Clean Up of Metalloids Using Three Plant Species in Iran

Phytoremediation is a potential, innovative, and cost-effective technology for non-destructive remediation of heavy-metal contaminated soils. A field trial was conducted to evaluate the phytoremediation efficiencies of three plants and the effects of ethylenediaminetetraacetic acid (EDTA) or ammonium addition [(NH4)2SO4 and NH4NO3] for assisting removal of heavy metals (Pb, Hg, and Cd) from contaminated soil. The tested plants include Amaranthus retroflexus, Sorghum bicolor, and Lolium perrene. Results showed that maximum concentration of Pb, Hg, and Cd were detected in shoots of A. retroflexus, S. bicolor, and L. perrene at high concentrations in pH=6.2. The application of EDTA as a chelating agent to soil was the most efficient to enhance the phytoavailability of Pb, Hg and Cd. The concentrations of Pb, Hg, and Cd in the shoots of A. retroflexus treated with EDTA were 57 mg/kg, 14.1 mg/kg, and 30 mg/kg, respectively. Results indicated that among the three plants, A. retroflexus had great potential in phytoremediation of contaminated soils.

Hydrocarbon stress response of four tropical plants in weathered crude oil contaminated soil in microcosms

Responses to hydrocarbon stress of four tropical plants Panicum maximum, Zea mays, Centrosema sp. and Pueraria sp. grown in crude oil contaminated soils (1%, 5% and 10% w/w) were evaluated in a green house. Plants’ percentage survival, shoot heights, biomass development, and phytotoxicity susceptibility were used as indicators of growth, stress response and hydrocarbon tolerance. Relative to control, shoot heights and biomass of plants reduced with increasing hydrocarbon concentration, but 1% w/w oil-in-soil, stimulated shoot heights (5.9% and 6.4%) and weights (21.9% and 2.3%) in P. maximum and Centrosema sp. respectively. P. maximum tolerated the contaminant stress with biomass yields of 113% and 57% of control respectively in 1% and 10% w/w oil-in-soil. All the plants had 100% survival in 1% w/w, but considerably reduced survival in 10% w/w oil-in-soil. These results show that P. maximum has great potential for phytoremediation of petroleum contaminated soil.

施肥对两种苋菜吸收积累镉的影响

通过盆栽试验,研究了生长在5 mg/kg 镉(Cd)污染土壤中的两种苋菜(红苋(<em>Amaranthus Paniculatus</em> L.)和绿苋(<em>Amaranthus Paniculatus</em> L.))在3种施肥处理下(N、NP和NPK)的生长状况和对Cd的吸收积累情况。结果表明,两种苋菜能够在污染土壤中正常生长,各器官中叶Cd含量最高,范围为124.1-225.9 mg/kg;根中次之,范围为57.1-100.6 mg/kg;茎中最低,范围为56.2-87.6 mg/kg;富集系数高达22.4-40.2。施加N, NP, NPK肥对两种苋菜器官中的Cd含量和生物量有显著影响。其中,施加NPK肥使红苋和绿苋的生物量分别达到不施肥(对照)处理的3.5和3.2倍,单株提取Cd的总量是对照3.2和5.0倍。综上表明,两种苋菜(红苋和绿苋)具有生物量大、易栽培、施加NPK肥能够大幅增加生物量的同时不减少器官对Cd的吸收等优点,作为Cd污染土壤的修复植物有巨大应用前景。;We assessed the phytoextraction potential for Cd of two edible amaranthus herbs (red amaranth: <em>Amaranth Paniculatus</em> L. and green amaranth: <em>Amaranth Paniculatus</em> L.)and the effect of application of N, NP and NPK fertilizers on Cd uptake of the two cultivars from soil contaminated with 5 mg/kg Cd. Two edible amaranthus herbs had high levels of Cd concentration in their tissues, ranging from 124.1 to 225.9 mg/kg in leaves, from 56.2 to 87.6 mg/kg in stems, and from 57.1 to 100.6 mg/kg in roots, resulting in average Bioaccumulation Factors(BCF) ranging from 22.4 to 40.2. Application of N, NP or NPK fertilizers had significantly influenced Cd content in leaves, stems and roots. Fertilizers of NPK fertilizer greatly increased dry biomass, by a factor of 3.5 for red amaranth or 3.2 for green amaranth, resulting in a large increment of Cd uptake per plant. Two edible amaranthus herbs have great potential in phytoremediation of Cd contaminated soil. They have the merits of high Cd content in tissues, high biomass, easy cultivation, and little effect on Cd uptake by fertilization.

Chemically Assisted Phytoextraction of Heavy Metal Contaminated Soils using Three Plant Species

Phytoextraction is a potential, innovative and cost-effective technology for non-destructive remediation of heavy metal-contaminated soils. A field trial was conducted to evaluate the phytoextraction efficiencies of three plants and the effects of EDTA or ammonium addition [(NH4)2SO4 and NH4NO3] for assisting heavy metal (Pb, Zn, and Cd) removal from contaminated soil. The tested plants include Viola baoshanensis, Vertiveria zizanioides, and Rumex K-1 (Rumex patientia × R. timschmicus). The application of EDTA soil was the most efficient to enhance the phytoavailability of Pb and Zn, but did not have significant effect on Cd. Lead phytoextraction rates of V. baoshanensis, V. zizanioides and Rumex K-1 were improved by 19-, 2-, and 13-folds compared with the control treatment, respectively. The application of ammonium did not have obvious effects on phytoextraction of the three metals, except that the accumulations of Zn and Cd in shoot of V. baoshanensis. Among the three tested plants, V. baoshanensis always accumulated the highest concentrations of Pb, Zn, and Cd. The concentrations of Pb, Zn, and Cd in the shoots of V. baoshanensis treated with EDTA were 624, 795, and 25 mg kg−1, respectively, and the phytoextraction efficiencies of this species for Pb, Zn, and Cd were also the highest among the three species. Results presented here indicated that V. baoshanensis had great potential in phytoremediation of soils contaminated by multiple heavy metals, although the dry weight yield was the lowest among the three plants.

Copper Uptake and Tolerance in Two Contrasting Ecotypes of Elsholtzia argyi

Information is desired on plant species that have a great potential in phytoremediation of copper (Cu) contaminated soils. Two contrasting ecotypes of Elsholtzia argyi were comparatively studied using nutrient solution culture for their growth response and uptake, distribution, and translocation of Cu. The results show that the ecotype from an old mined area (Sanmen-ecotype) had greater tolerance to Cu than that from the nonmined area (Jiuxi-ecotype) based on dry matter yield at different Cu supply levels. Inhibited root and leaf growth was noted at the external Cu levels > 50 µmol L−1 for the Sanmen-ecotype, and at the Cu supply levels > 5 µmol L−1 for the Jiuxi-ecotype. Stem growth was most sensitive to Cu toxicity in E. argyi, and was inhibited at the Cu levels ≥ 2.5 µmol L−1 for Jiuxi-ecotype and ≥ 25 µmol L−1 for Sanmen-ecotype. Root Cu concentrations were higher in Sanmen-ecotype than in Jiuxi-ecotype, but leaf, especially stem Cu concentrations were much lower in the former than in the latter. Furthermore, Jiuxi-ecotype was much more efficient than Sanmen-ecotype in the translocation of Cu from root to the shoot, and it had higher ratios of stem/root and leaf/root Cu concentration. At the Cu supply levels higher than 10 µmol L−1, root concentrations of potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) considerably decreased in Jiuxi-ecotype, but were not affected or even increased in Sanmen-ecotype. Zinc concentrations in the stems, particularly in the leaves of Sanmen-ecotype increased by 3 folds, but were hardly changed in Juixi-ecotype when grown at the Cu levels higher than 10 µmol L−1. These results indicate that the Sanmen-ecotype of E. argyi is a Cu-tolerant ecotype, and its tolerance to high Cu levels was mainly related to its extraordinary capability to restrict Cu uptake, especially Cu translocation from root to the shoot, probably by competitive uptake and translocation of Zn.

GROWTH AND NUTRIENT COMPOSITION OF ELSHOLTZIA SPLENDENS NAKAI UNDER COPPER TOXICITY

ABSTRACT Copper (Cu) tolerance and accumulation in Elsholtzia splendens Nakai were investigated by means of hydroponic culture. Enhanced growth was observed when plants were exposed to 50 and 100 µM Cu. Copper uptake efficiency and translocation depended on Cu concentration in nutrient solution. Shoot Cu concentrations of 1133 and 3417 µg g−1 dry wt were achieved by 500 and 1000 µM Cu supply, respectively. Copper accumulation in E. splendens was accompanied by the ability to maintain the concentrations of other essential nutrients, except potassium, within the range considered sufficient for normal growth of higher plants. The results obtained suggest that E. splendens has a great potential for phytoremediation.