Cadmium Accumulation In Roots Research Articles

Phosphorus deficiency-induced cell wall pectin demethylesterification enhances cadmium accumulation in roots of Salix caprea

Regions affected by heavy metal contamination frequently encounter phosphorus (P) deficiency. Numerous studies highlight crucial role of P in facilitating cadmium (Cd) accumulation in woody plants. However, the regulatory mechanism by which P affects Cd accumulation in roots remains ambiguous. This study aims to investigate the effects of phosphorus (P) deficiency on Cd accumulation, Cd subcellular distribution, and cell wall components in the roots of Salix caprea under Cd stress. The results revealed that under P deficiency conditions, there was a 35.4% elevation in Cd content in roots, coupled with a 60.1% reduction in Cd content in shoots, compared to the P sufficiency conditions. Under deficient P conditions, the predominant response of roots to Cd exposure was the increased sequestration of Cd in root cell walls. The sequestration of Cd in root cell walls increased from 37.1% under sufficient P conditions to 66.7% under P deficiency, with pectin identified as the primary Cd binding site under both P conditions. Among cell wall components, P deficiency led to a significant 31.7% increase in Cd content within pectin compared to P sufficiency conditions, but did not change the pectin content. Notably, P deficiency significantly increased pectin methylesterase (PME) activity by regulating the expression of PME and PMEI genes, leading to a 10.4% reduction in the degree of pectin methylesterification. This may elucidate the absence of significant changes in pectin content under P deficiency conditions and the concurrent increase in Cd accumulation in pectin. Fourier transform infrared spectroscopy (FTIR) results indicated an increase in carboxyl groups in the root cell walls under P deficiency compared to sufficient P treatment. The results provide deep insights into the mechanisms of higher Cd accumulation in root mediated by P deficiency.

SbYS1 and SbWRKY72 regulate Cd tolerance and accumulation in sweet sorghum.

SbYS1 and its upstream transcription factor SbWRKY72 were involved in Cd tolerance and accumulation and are valuable for developing sweet sorghum germplasm with high-Cd tolerance or accumulation ability through genetic manipulation. Cadmium (Cd) is highly toxic and can severely affect human health. Sweet sorghum, as an energy crop, shows great potential in extracting cadmium from Cd-contaminated soils. However, its molecular mechanisms of Cd-tolerance and -accumulation remain largely unknown. Here, we isolated a YSL family gene SbYS1 from the sweet sorghum genotype with high Cd accumulation ability and the expression of SbYS1 in roots was induced by cadmium. GUS staining experiment exhibited that SbYS1 was expressed in the epidermis and parenchyma tissues of roots. Further subcellular localization analysis suggested that SbYS1 was localized in the endoplasmic reticulum and plasma membrane. Yeast transformed with SbYS1 exhibited a sensitive phenotype compared to the control when exposed to Cd-NA (chelates of cadmium and nicotianamine), indicating that SbYS1 may absorb cadmium in the form of Cd-NA. Arabidopsis overexpressing SbYS1 had a longer root length and accumulated less Cd in roots and shoots. SbWRKY72 bound to the promoter of SbYS1 and negatively regulated the expression of SbYS1. Transgenic Arabidopsis of SbWRKY72 showed higher sensitivity to cadmium and increased cadmium accumulation in roots. Our results provide references for improving the phytoremediation efficiency of sweet sorghum by genetic manipulation in the future.

Physiological and transcriptomic characterization of cadmium toxicity in Moso bamboo (Phyllostachys edulis), a non-timber forest species.

Cadmium pollution in Moso bamboo forests poses a potential threat to the sustainable development of the bamboo industry. However, the effects of cadmium toxicity on Moso growth and its mechanisms of adaptation to cadmium stress are poorly understood. In this study, the physiological and transcriptional response of Moso to cadmium stress was investigated in detail using Moso seedlings in a hydroponic system. Cadmium toxicity severely inhibited the growth of roots but had little effect on biomass accumulation in the aerial parts. Cadmium accumulation in roots and aerial parts increased as external cadmium increased, with cadmium mainly localized in the epidermis and pericycle cells in the roots. The uptake and root-to-shoot translocation of cadmium was stimulated, but the photosynthetic process was suppressed under cadmium stress. A total of 3469 differentially expressed genes were identified from the transcriptome profile and those involved in cadmium uptake, transportation and detoxification were analyzed as candidates for having roles in adaptation to cadmium stress. The results suggested that Moso is highly efficient in cadmium uptake, xylem loading and translocation, as well as having a high capacity for cadmium accumulation. This work also provided basic information on physiological and transcriptional responses of Moso to cadmium toxicity.

Absorption of Cadmium and its Effect on the Growth of Halfsib Family of Three Cocoa Clones Seedling

The issue of cadmium in cocoa beans has become one of the primary considerations in setting quality criteria in chocolate-consuming countries. Using rootstock genotypes that are tolerant to cadmium uptake can provide data on the absorption of cadmium into shoots for recovery. This study examined cocoa plants’ growth and physiological response to cadmium (Cd) accumulation. The research was carried out using polybags in the Greenhouse of the Indonesian Coffee and Cocoa Research Center using a half-sib family of cocoa aged 4 months after sowing. The study was designed using a completely randomized split-plot design with 3 replications. The parent plots were the half-sib families of Sulawesi 1, Sulawesi 2, and Scavina 6. The subplots were added with cadmium solution at 0 (control), 2, 4, and 8 ppm. The results showed that adding cadmium up to 8 ppm did not affect the growth and biomass of cocoa seedlings; however, it had a negative effect on plant physiological processes of the net assimilation rate and relative growth rate. Cadmium content in the tissue increased with increasing cadmium concentration in the growing medium. The accumulation of cadmium in roots was higher than that of shoots. Absorption of cadmium in the root tissue of Sulawesi 1 was higher than that of Scavina 6 and Sulawesi 2; genetic factors did not affect cadmium uptake in the shoots. There was a positive correlation between root dry weight and cadmium concentration in the tissue; the higher the dry weight of the root tissue, the higher the cadmium uptake in plants.

The R2R3-MYB transcription factor ThRAX2 recognized a new element MYB-T (CTTCCA) to enhance cadmium tolerance in Tamarix hispida

R2R3-MYB transcription factors play an important role in plant development and response to various environmental stresses. In this study, a new R2R3-MYB gene, named ThRAX2, was isolated from T. hispida. ThRAX2 has an open reading frame (ORF) of 1191 bp and encodes a protein of 396 amino acids. ThRAX2 was localized in the nucleus. The overexpression of ThRAX2 in Arabidopsis and T. hispida significantly increased Cadmium (Cd) tolerance. Moreover, the accumulation of cadmium in roots and leaves was significantly reduced. The TF-centred Y1H and Y1H results showed that ThRAX2 was able to specifically bind a new cis-element (MYB-T, CTTCCA). The promoters of some Cd-responsive genes, such as ThSOS1, ThCKX3, ThCAX3A, ThMYB78, ThMIP2, ThTPS4, and ThSOD2, all contained 1–3 MYB-T sequences. Furthermore, chromatin immunoprecipitation-polymerase chain reaction (ChIP-PCR) and ChIPquantitative (q)PCR showed that the ThRAX2 gene can bind to ThSOS1, ThCKX3, ThCAX3A and ThMYB78 promoter fragments, including the MYB-T motif. Meanwhile, the qRTPCR results also showed that the expression trends of ThSOS1, ThCKX3, ThCAX3A and ThMYB78 were similar to that of ThRAX2. This finding suggests that Cd tolerance of the ThRAX2 gene may regulate the expression of some downstream genes through specific recognition of the MYB-T motif and participate in regulating intracellular ion homeostasis, transport, and protein activity or enhance antioxidant enzyme activity. This study found a novel cis-acting element that binds ThRAX2 to regulate Cd tolerance, which lays the foundation for the ThRAX2 regulatory mechanism of Cd stress. This study provides a genetic and theoretical basis for the bioremediation of Cd-contaminated land by cultivating transgenic plants in the future.

The ameliorative effect of hydrogen sulfide on cadmium toxicity and oxidative stress damage in garlic (Allium sativum) seedlings

• H 2 S reduces the uptake and accumulation of cadmium in garlic plants. • H 2 S reducing Cd oxidative damages by adjusting antioxidant enzyme system. • H 2 S considerably balanced Fe and Na in garlic seedlings. • H 2 S ameliorator improved the photosynthetic rate of garlic seedlings. Hydrogen sulfide (H 2 S) was identified as a novel signaling molecule that plays roles in plant growth and responses to abiotic stresses. However, information regarding its role in cadmium (Cd) detoxification and possible beneficial effects against oxidative damage in garlic plants is lacking. In this study, garlic ( Allium sativum ) seedlings were grown hydroponically at 0, 10 −4 , 10 −3 and 10 −2 M of cadmium chloride (CdCl 2 ) and 0, 200 µM concentrations of sodium hydrosulfide (NaHS). Cadmium stress caused growth inhibition and biomass reduction, which was related to high accumulation of cadmium in roots and shoots, depletion of chlorophyll contents, decrease of photosynthetic parameters and imbalanced in essential elements. These changes were accompanied by increasing activities of superoxide dismutase and ascorbate peroxidase enzymes while catalase enzyme activity decreased. The treatment with H 2 S ameliorator reduced Cd accumulation in seedling and improved photosynthetic rate of plants. This conclusion was supported by the increase of superoxide dismutase and ascorbate peroxidase activities as well as the balanced to mineral element uptake. Based on the results, it can be concluded that exogenous H 2 S has a positive effect on reducing Cd oxidative damages by adjusting antioxidant enzyme system and balances in nutrient element uptake, thus proposing H 2 S as a candidate for managing toxicity of cadmium in garlic plants.

Hydrogen Peroxide Mediates Cadmium Accumulation in Root of High Cadmium-Accumulating Rice (Oryza Sativa L.) Line

Hydrogen Peroxide Mediates Cadmium Accumulation in Root of High Cadmium-Accumulating Rice (Oryza Sativa L.) Line

Phenotypic and genetic dissection of cadmium accumulation in roots, nodes and grains of rice hybrids

Rice accumulates higher levels of cadmium (Cd) in grain than other cereals, and hybrid rice varieties cover around half of the total rice area in China. Therefore, understanding the phenotypic and genetic characteristics of Cd accumulation in rice hybrids is vital for food safety. An incomplete diallel cross design was used to analyse the heritability and combining ability of Cd accumulation in rice hybrids growing in soil contaminated with Cd. The quantitative real-time PCR was used to detect the gene expressions that related to Cd uptake and transport. The Cd contents in brown rice, nodes and roots were detected by ICPOES, and the Cd contents in xylem sap were detected by ICPMS. Additive effects dominated the Cd accumulation in brown rice, upper nodes, and the Cd translocation efficiency from roots to nodes of hybrids. The Cd accumulation in brown rice was positively correlated with Cd accumulation in upper nodes and translocation efficiency from roots to nodes. Regarding the general combining ability, the restorer lines R2292 and R2265, and the male sterile lines KeBX58S, Ke20A, Ke76-1BS and Ke244-1BS were found to be potential elite parental lines for developing hybrid rice with low Cd accumulation. Hybrid rice with low Cd accumulation in brown rice can be derived from parental lines with low general combining ability for Cd content in brown rice.

Hydrogen sulfide ameliorates cadmium chloride injury in seedlings of Malus hupehensis by reducing influx and accumulation of cadmium in roots

Hydrogen sulfide ameliorates cadmium chloride injury in seedlings of <i>Malus hupehensis</i> by reducing influx and accumulation of cadmium in roots

Populus euphratica annexin1 facilitates cadmium enrichment in transgenic Arabidopsis

Phytoremediation offers a great potential for affordable remediation of heavy metal (HM)−polluted soil and water. Screening and identifying candidate genes related to HM uptake and transport is prerequisite for improvement of phytoremediation by genetic engineering. Using the cadmium (Cd)−hypersensitive Populus euphratica, an annexin encoding gene facilitating Cd enrichment was identified in this study. With a 12 h exposure to CdCl2 (50–100 μM), P. euphratica cells down-regulated transcripts of annexin1 (PeANN1). PeANN1 was homologue to Arabidopsis annexin1 (AtANN1) and localized mainly to the plasma membrane (PM) and cytosol. Compared with wild type and Atann1 mutant, PeANN1 overexpression in Arabidopsis resulted in a more pronounced decline in survival rate and root length after a long-term Cd stress (10 d, 50 μM), due to a higher cadmium accumulation in roots. PeANN1−transgenic roots exhibited enhanced influx conductance of Cd2+ under cadmium shock (30 min, 50 μM) and short-term stress (12 h, 50 μM). Noteworthy, the PeANN1-facilitated Cd2+ influx was significantly inhibited by a calcium-permeable channel (CaPC) inhibitor (GdCl3) but was promoted by 1 mM H2O2, indicating that Cd2+ entered root cells via radical-activated CaPCs in the PM. Therefore, PeANN1 can serve as a candidate gene for improvement of phytoremediation by genetic engineering.

Ethylene-mediated apoplastic barriers development involved in cadmium accumulation in root of hyperaccumulator Sedum alfredii

Ethylene is an important phytohormone for plant adaptation to heavy metal stress. However, the effects of ethylene on radial apoplastic transport of Cd remain elusive. This study investigated the role of ethylene on apoplastic barriers development and consequences for Cd uptake in Sedum alfredii. In response to Cd, endogenous ethylene production in hyperaccumulating ecotype (HE) roots was decreased due to the down-regulated expressions of ethylene biosynthesis genes, while the opposite result was observed in non-hyperaccumulating ecotype (NHE). Interestingly, the ethylene emission in HE was always higher than that in NHE, regardless of Cd concentrations. Results of exogenous application of ethylene biosynthesis precursor/inhibitor indicate that ethylene with high level would delay the formation of apoplastic barriers in HE through restraining phenylalanine ammonia lyase activity and gene expressions related to lignin/suberin biosynthesis. Simultaneously, correlation analyses suggest that Cd-induced apoplastic barriers formation may be also regulated by ethylene signaling. By using an apoplastic bypass tracer and scanning ion-selected electrode, we observed that the delayed deposition of apoplastic barriers significantly promoted Cd influx in roots. Taken together, high endogenous ethylene in HE postponed the formation of apoplastic barriers and thus promoted the Cd accumulation in the apoplast of roots.

Phytoremediation effect of Medicago sativa colonized by Piriformospora indica in the phenanthrene and cadmium co-contaminated soil

BackgroundThe coexistence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals has deleterious effects on environmental quality. Few reports have studied the mechanisms of plant inoculation with Piriformospora indica to remediate PAH-metal co-contaminated soil by analyzing the chemical speciation of the contaminants. This study investigated the influence of the inoculation of Medicago sativa with P. indica to remediate soil co-contaminated with phenanthrene (a kind of PAH) and cadmium (a heavy metal) by analyzing plant growth, physiological parameters and chemical speciation in rhizosphere and nonrhizosphere soils.ResultsThe presence of P. indica significantly increased plant tolerance, chlorophyll a, chlorophyll b, maximum quantum efficiency of PSII photochemistry and electron transport rate values in phenanthrene- and/or cadmium-contaminated soil. P. indica inoculation in M. sativa roots increased fluorescein diacetate activities in soils contaminated with phenanthrene, cadmium or both, especially in the nonrhizosphere. The presence of phenanthrene prevented the inoculated plant from accumulating cadmium to some extent, whereas the presence of cadmium did not prevent the degradation of phenanthrene in either the rhizosphere or the nonrhizosphere after P. indica colonization. Although the low bioavailability of cadmium in the rhizosphere restricted its transportation into the stem, P. indica colonization in plants effectively increased cadmium accumulation in roots in soil co-contaminated with cadmium and phenanthrene.ConclusionsIn conclusion, this work provides a theoretical basis for the use of P. indica combined with M. sativa for the remediation of PAH-metal co-contaminated soil.

Exogenous spermidine elevating cadmium tolerance in Salix matsudana involves cadmium detoxification and antioxidant defense

In this study, exogenous spermidine role on Salix matsudana tolerance to cadmium was evaluated. Spermidine and cadmium presented antagonistic effects on the biomass, copper and zinc concentrations in S. matsudana. cadmium mainly distributed in the cell wall of subcellular fraction; 46.97%–60.43% of cadmium existed in a sodium chloride-extracted form. Cadmium contents in roots, leaves, and twigs ranged from 2002.67 to 3961.00, 111.59 to 229.72, and 102.56 to 221.27 mg/kg, respectively. Spermidine application elevated cadmium concentrations in the roots, cuttings, and cell wall and the ratio of deionized water-extracted cadmium, but decreased cadmium levels in the twigs and leaves and the fractions of cadmium extracted by ethanol and sodium chloride, respectively. Putrescine and malondialdehyde were important indicators of cadmium-induced oxidative damage. Exogenous spermidine alleviated the accumulation of superoxide anion, hydrogen peroxide, malondialdehyde via promoting the levels of spermidine, soluble protein, superoxide dismutase, reductive ascorbate, glutathione reductase, and glutathione peroxidase in S. matsudana leaves under the corresponding cadmium stress. The results indicated that S. matsudana was a candidate for cadmium rhizoremediation and extraction in leaves; the spermidine application enhanced the cadmium tolerance of S. matsudana through promoting cadmium accumulation in roots, cell wall, and less bioactive chemical forms and the antioxidative ability.

Effect of cadmium stress on morpho-physiological traits in garden cress and radish in an aeroponic system

Cadmium is a main toxic pollutant and poses a considerable threat to human health. In other to study the effect of Cd stress on traits of garden cress and radish, an experiment was conducted based on a completely randomized design in an aeroponic system. In this study CdCl2 was used at three levels (control, 3, and 6 mgl-1). Seeds were cultivated in an aeroponic system and Hoagland nutrient solutions (with and without Cd) were used for irrigation. Morphological traits and cadmium accumulation were measured after 40 days. Results for garden cress showed the highest plant height (32.67 cm), leaf number (30.83), root length (14.5 cm), dry weights of roots (0.34 g) and shoots (1.52 g), fresh weights of roots (2.27 g) and shoots (11.3 g) in the control and the 6 mg l-1 cadmium chloride resulted in the highest cadmium accumulation in roots and shoots 2.88 and 0.11 kg/g, respectively. Also in radish the results showed the highest plant height (50.1 cm), leaf number (18.8), root length (26.7 cm), dry weights of roots (0.41 g) and shoots (2.04 g), fresh weights of roots (3.9 g) and shoots (27.01 g) in the control and the 6 mg l-1 cadmium chloride produced the highest cadmium accumulation in roots and shoots 3.3 and 0.28 kg/g, respectively. Findings showed that proline, total phenol, and anthocyanin contents increased under cadmium stress in garden cress and radish.

Biological removal of cadmium from soil by phytoremediation and its impact on growth parameters, photosynthetic pigments, phenol and malondealdehyde content in Vetiveria zizianoides.

Phytoremediation is one of the most widely used methods for removing soil contaminants. In this research, the function of Vetiveria zizianoides to remove cadmium from four different treatments with varying amounts of cadmium chloride contamination (including 0, 20, 40, and 60 mg per liter) was investigated and physiological changes caused by the accumulation of this metal in the plant were monitored. According to the obtained results, cadmium accumulation in roots was higher as compared to the shoots. Based on factors such as the amount of biomass and the length of organs, the growth rate was reduced in plants accumulating more cadmium. Our findings also showed that increased concentrations of cadmium chloride in the experimental units caused a significant reduction of photosynthetic pigments compared to control. However, phenolic compounds and malondialdehyde showed a significant increase with increasing concentrations of cadmium chloride. In addition, the cadmium uptake by the plant was increased with increasing concentration of cadmium chloride. Our results clearly showed the high capability of Vetiveria zizianoides for biological removal of cadmium from contaminated soil.

In situ phytostabilisation capacity of three legumes and their associated Plant Growth Promoting Bacteria (PGPBs) in mine tailings of northern Tunisia

PGPBs-legumes associations represent an alternative procedure for phytostabilisation of heavy metals polluted soils mainly generated by industrial and agricultural practices.In this study we evaluated the capacity of Vicia faba, Lens culinaris and Sulla coronaria, inoculated in situ by specific heavy metals resistant inocula, for the phytostabilisation of copper, lead and cadmium respectively. The experimentation was performed in mine tailings of northern Tunisia. Results proved that inoculation enhanced roots and shoots biomass production of faba bean by 14% and 12%, respectively, and significantly improved pods yield by 91%. In lentil, the inoculation ameliorated shoot biomass up to 27%. The highest nitrogen fixation was recorded by Sulla coronaria. The three symbioses accumulated heavy metals essentially in roots, and poorly in shoots. In addition, cadmium accumulation in roots of inoculated sulla was enhanced by 39%. Furthermore, inoculations decreased heavy metals availability in the soil up to −10% of Cu and −47% of Pb respectively in roots of faba bean and lentil. Our results suggested a positive effect of co-inoculation of legumes by appropriate heavy metals resistant PGPBs for the phytostabilisation of mine tailings. Elsewhere, the enhancement in the antioxidant enzymes activities demonstrated the role of the three inocula to alleviate the heavy metals induced stress.

Exogenous malic and acetic acids reduce cadmium phytotoxicity and enhance cadmium accumulation in roots of sunflower plants

There is increasing evidence showing that low molecular weight organic acids (LMWOA) are involved in heavy metal resistance mechanisms in plants. The aim of this study was to investigate the effects of exogenous malic (MA) or acetic (AA) acids on the toxicity and accumulation of cadmium (Cd) in sunflower (Helianthus annuus L.). For this purpose, plants were grown in hydroponics under controlled conditions. Single Cd stress (5 μM Cd for 14 days) induced strong phytotoxic effects, as indicated by a decrease in all growth parameters, concentration of photosynthetic pigments, and root activity, as well as a high level of hydrogen peroxide (H2O2) accumulation. Exogenous MA or AA (250 or 500 μM) applied to the Cd-containing medium enhanced the accumulation of Cd by the roots and limited Cd translocation to the shoots. Moreover, the MA or AA applied more or less reduced Cd phytotoxicity by increasing the growth parameters, photosynthetic pigment concentrations, decreasing accumulation of H2O2, and improving the root activity. Of the studied organic acids, MA was much more efficient in mitigation of Cd toxicity than AA, probably by its antioxidant effects, which were stronger than those of AA. Plant response to Cd involved decreased production of endogenous LMWOA, probably as a consequence of severe Cd toxicity. The addition of MA or AA to the medium increased endogenous accumulation of LMWOA, especially in the roots, which could be beneficial for plant metabolism. These results imply that especially MA may be involved in the processes of Cd uptake, translocation, and tolerance in plants.

Hyperaccumulator Oilcake Manure as an Alternative for Chelate-Induced Phytoremediation of Heavy Metals Contaminated Alluvial Soils

The ability of hyperaccumulator oilcake manure as compared to chelates was investigated by growing Calendula officinalis L for phytoremediation of cadmium and lead contaminated alluvial soil. The combinatorial treatment T6 [2.5 g kg−1oilcake manure + 5 mmol kg−1 EDDS] caused maximum cadmium accumulation in root, shoot and flower up to 5.46, 4.74 and 1.37 mg kg−1and lead accumulation up to 16.11, 13.44 and 3.17 mg kg−1, respectively at Naini dump site, Allahabad (S3). The treatment showed maximum remediation efficiency for Cd (RR = 0.676%) and Pb (RR = 0.202%) at Mumfordganj contaminated site (S2). However, the above parameters were also observed at par with the treatment T5 [2.5 g kg−1oilcake manure +2 g kg−1 humic acid]. Applied EDDS altered chlorophyll–a, chlorophyll–b, and carotene contents of plants while application of oilcake manure enhanced their contents in plant by 3.73–8.65%, 5.81–17.65%, and 7.04–17.19%, respectively. The authors conclude that Calendula officinalis L has potential to be safely grown in moderately Cd and Pb-contaminated soils and application of hyperaccumulator oilcake manure boosts the photosynthetic pigments of the plant, leading to enhanced clean-up of the cadmium and lead-contaminated soils. Hence, the hyperaccumulator oilcake manure should be preferred over chelates for sustainable phytoremediation through soil-plant rhizospheric process.

The high potential of Pelargonium roseum plant for phytoremediation of heavy metals.

The major objective of this investigation was to evaluate the potential of scented geraniums, Pelargonium roseum, to uptake and accumulate heavy metals nickel (Ni), cadmium (Cd), or lead (Pb). For this, plants were grown in an artificial soil system and exposed to a range of metal concentrations over a 14-day treatment period. Then, metals from the entire biomass were extracted. The results showed that scented geranium plants accumulated in excess of 20,055 mg of Ni kg−1 dry weight (DW) of root and 10,889 mg of Ni kg−1 DW of shoot, and in excess of 86,566 mg of Pb kg−1 DW for roots and 4,416 mg of Pb kg−1 DW for shoots within 14 days. Also, the uptake and accumulation of cadmium in roots of scented geranium plants increased with the exposure at low (250, 500 mg L−1) and medium level (750 mg L−1) followed by a decline at the highest level (1,000 mg L−1). The highest accumulation in roots (31,267 mg kg−1 DW) was observed in 750 mg L−1 cadmium treatment. In the shoots of scented geraniums, the highest amount of metal accumulation (1,957 mg kg−1 DW) was detected at 750 and 1,000 mg L−1 of cadmium in the culture solution. Finally, since the high concentrations of Ni or Pb accumulated in shoots of scented geranium has far exceeded 0.1 % DW and for Cd has far exceeded 0.01 % DW, P. roseum is a new hyperaccumulator species for these metals and can be used in phytoremediation industry.

Screening of Poplar Clones for Cadmium Phytoremediation Using Photosynthesis, Biomass and Cadmium Content Analyses

Variability of cadmium tolerance and distribution in plant organs was investigated in ten selected poplar clones from different species, hybrids and genotypes. To this end, plants were exposed for three weeks to 50 μM CdSO4 in hydroponics. Cadmium accumulation in roots, stem and leaves as well as biomass production and photosynthesis maintenance varied greatly among clones. The metal mostly accumulated in roots, up to 80% in some clones, and interestingly, only 50% in some others. In general, metal tolerance reflected the degree of photosynthesis inhibition, which was higher in clones with high cadmium accumulation in leaves. Biomass production, net photosynthesis, transpiration, and pigment content were differently reduced in cadmium-treated clones with respect to control. The variability of cadmium distribution among leaves, stem, and roots provides candidate poplars for specific phytoremediation processes of contaminated waters and soils.