Metals In Plant Tissues Research Articles

SR induced micro-XRF for studying the spatial distribution of Pb in plants used for soil phytoremediation

The phytoextraction technology uses vegetable species to extract toxic metals from contaminated soils and accumulate them in the harvestable parts of the plants, which can then be removed from site.The aim of this work was to perform a study by SR micro X-ray fluorescence technique of the spatial distribution of Pb in roots and leaves of two different species of plants potentially useful for soil phytoremediation.The experiments were conducted in Brassica napus and Festuca arundinacea. The plants were grown in Pb soil contaminated, in controlled environment, cultivated in greenhouses at CEPROCOR.The measurements were carried on at the D09B XRF Fluorescence beamline of the Brazilian Synchrotron Light Laboratory (LNLS), on different parts of the living plant.SR induced micro-XRF results showed that Brassica napus extracted Pb from the ground and translocated it to the leaves more effectively than Festuca arundinacea, grown in contaminated soil, where lead remained at the root. Furthermore, a co-distribution was observed between Pb and Zn, P, S and Fe. This suggest that Brassica napus is a potential plant to be used for phytoextraction of Pb from soil.The use of SR micro-XRF to map the distribution of metals in plant tissue allows significant advances in phytoremediation studies as well as in other topics of environmental sciences.

Genome-wide characterization of the NRAMP gene family in Phaseolus vulgaris provides insights into functional implications during common bean development.

Transporter proteins play an essential role in the uptake, trafficking and storage of metals in plant tissues. The Natural Resistance-Associated Macrophage Protein (NRAMP) family plays an essential role in divalent metal transport. We conducted bioinformatics approaches to identify seven NRAMP genes in the Phaseolus vulgaris genome, investigated their phylogenetic relation, and performed transmembrane domain and gene/protein structure analyses. We found that the NRAMP gene family forms two distinct groups. One group included the PvNRAMP1, -6, and -7 genes that share a fragmented structure with a numerous exon/intron organization and encode proteins with mitochondrial or plastidial localization. The other group is characterized by few exons that encode cytoplasmic proteins. In addition, our data indicated that PvNRAMP6 and -7 may be involved in mineral uptake and mobilization in nodule tissues, while the genes PvNRAMP1, -2, -3, -4 and -5 are potentially recruited during plant development. This data provided a more comprehensive understanding of the role of NRAMP transporters in metal homeostasis in P. vulgaris.

Expressions of glutathione-related genes and activities of their corresponding enzymes in leaves of tomato exposed to heavy metal

Plant development depends on the environmental conditions, and the accumulation of heavy metals in plant tissues causes various molecular and biochemical changes in plant life cycles. Plants have developed a number of detoxification mechanisms to tolerate oxidative damages in the unsuitable environments. GR and GST involved with glutathione are the key antioxidant defense enzymes in response to heavy metals stress. In the present study, mRNA expressions and activities of GR and GST enzymes are investigated in the leaves of tomato (Lycopersicon esculentum Mill.) increasing doses of Cd, Cu, and Pb. The transcriptional expression of GR and GST was analyzed by real-time quantitative PCR. GR and GST genes are induced compared to control in leaves of tomato by the application of heavy metals. The expression of GR usually significantly increased except for 10 ppm of Pb which there was no significant change in the low dose. The GST transcript significantly raised in all treatment of heavy metals. The highest expression of GR and GST was observed in the application of 20 and 50 ppm of Pb, respectively. The enzyme activities of GR and GST significantly increased by the application of Cd, Cu, and Pb, but GR activity remained constant at 50 ppm of Cu compared to control in leaves of tomato. The results presented in this study indicate that the transcript expressions show a correlation with enzymes activities with small differences because post-transcriptional factors might affect the enzymes activities.

Amelioration of iron mine soils with biosolids: Effects on plant tissue metal content and earthworms.

The achievement of environmentally sound and economically feasible disposal strategies for biosolids is a major issue in the wastewater treatment industry around the world, including Swaziland. Currently, an iron ore mine site, which is located within a wildlife sanctuary, is being considered as a suitable place where controlled disposal of biosolids may be practiced. Therefore, this study was conducted to investigate the effects of urban biosolids on iron mine soils with regard to plant metal content and ecotoxicological effects on earthworms. This was done through chemical analysis of plants grown in biosolid-amended mine soil. Earthworm behaviour, reproduction and bioaccumulation tests were also conducted on biosolid-amended mine soil. According to the results obtained, the use of biosolids led to creation of soil conditions that were generally favourable to earthworms. However, plants were found to have accumulated Zn up to 346mgkg-1 (in shoots) and 462mgkg-1 (in roots). This was more than double the normal Zn content of plants. It was concluded that while biosolids can be beneficial to mine soils and earthworms, they can also lead to elevated metal content in plant tissues, which might be a concern to plant-dependant wildlife species. Nonetheless, it was not possible to satisfactorily estimate risks to forage quality since animal feeding tests with hyperaccumulator plants have not been reported. Quite possibly, there may be no cause for alarm since the uptake of metals from soil is greater in plants grown in pots in the greenhouse than from the same soil in the field since pot studies fail to mimic field conditions where the soil is heterogeneous and where the root system possesses a complex topology. It was thought that further field trials might assist in arriving at more satisfactory conclusions.

Selection of a suitable plant for phytoremediation in mining artisanal zones

ABSTRACTA study was undertaken with the aim of identifying a suitable plant for the phytoremediation of metal-polluted soil from an artisanal mining area in Ecuador. Three zones including a natural zone (NZ), abandoned zone (AZ) and intensively mined zone (IZ) were selected. Three common native plants grown in the three zones were identified and collected, including Miconia zamorensis, Axonopus compressus and Erato polymnioides. The percentage of arbuscular mycorrhizal colonization that benefits their own survival in polluted soil was analyzed in the root samples of these candidate species. Analysis of the soils and plants collected from the different zones showed that the concentrations of Pb, Zn, Cu and Cd were comparatively lower in the NZ, higher in the AZ and IZ, and highest in the AZ for all the metals. The concentration of all these metals in plant tissues was the highest in E. polymnioides. The data analysis including the metal accumulation index, bioconcentration factor and translocation factor strongly identified E. polymnioides as a hyperaccumulator plant suitable for phytoremediation.

Assessment of toxicological health risk of trace metals in vegetables mostly consumed in Punjab, Pakistan

In the present study, levels of trace metals in two commonly consumed vegetables (Spinacia oleracea and Brassica campestris) were assessed. Both vegetables are cultivated in a semi-arid area which receives effluents from various sources. Leafy parts and tender stems are used for human consumption as well as for farm animals as a source of nourishment. However, the aim of the present study was to appraise the concentrations of trace metals in different tissues of both vegetables at the time of harvesting when they become accessible to the humans. The analysis showed that mean trace metal levels in the stem of S. oleracea showed the highest bioconcentration of Zn (25.43 mg kg−1), while in the stem (28.56 mg kg−1) and roots (22.40 mg kg−1), Fe level was the highest. In case of B. campestris, Fe level was highest (18.45 mg kg−1) in the stems. Copper (Cu) has the highest bioconcentration factor values (BF = 1.030) in the stem of B. campestris, whereas Mn (BF = 0.010) was the least accumulated element in the leaves and roots of B. campestris. Collectively, bioconcentration of trace metals in plant tissues exceeded the standard values set by the World Health Organization (WHO) and the US Environmental Protection Agency. So, the vegetables cultivated in effluent-impacted areas may stance a potential public health risk for end-consumers.

Background levels of some major, trace, and rare earth elements in indigenous plant species growing in Norway and the influence of soil acidification, soil parent material, and seasonal variation on these levels.

Baseline levels of 43 elements, including major, trace, and rare earth elements (REEs) in several native plant species growing in boreal and alpine areas, are presented. Focus is placed on species metal levels at different soil conditions, temporal variations in plant tissue metal concentrations, and interspecies variation in metal concentrations. Vegetation samples were collected at Sogndal, a pristine site in western Norway, and at Risdalsheia, an acidified site in southernmost Norway. Metal concentrations in the different species sampled in western Norway are compared with relevant literature data from Norway, Finland, and northwest Russia, assumed to represent natural conditions. Except for aluminium (Al) and macronutrients, the levels of metals were generally lower in western Norway than in southern Norway and may be considered close to natural background levels. In southern Norway, the levels of cadmium (Cd) and lead (Pb) in particular appear to be affected by air pollution, either by direct atmospheric supply or through soil acidification. Levels of some elements show considerable variability between as well as within plant species. Calcium (Ca), magnesium (Mg), and potassium (K) are higher in most species at Sogndal compared to Risdalsheia, despite increased extractable concentrations in surface soil in the south, probably attributed to different buffer mechanisms in surface soil. Antagonism on plant uptake is suggested between Ca, Mg, and K on one hand and Al on the other. Tolerance among calcifuges to acid conditions and a particular ability to detoxify or avoid uptake of Al ions are noticeable for Vaccinium vitis-idaea.

Copper accumulation and changes in soil physical–chemical properties promoted by native plants in ​​an abandoned mine site in northeastern Brazil: Implications for restoration of mine sites

In this study, the copper-accumulating capacity of plants growing spontaneously in copper-contaminated soils in an ​​abandoned mine site in northeastern Brazil was evaluated by calculating enrichment (EF) and translocation (TF) factors. The effects of physical and chemical changes in the rhizosphere soil on copper mobility were determined by using different compounds (Mehlich3/MgCl2) to extract Cu from different types of soil samples (bulk/rhizosphere soil). Finally, the possible implications for the use of these plant species in restoring the area were assessed by calculating the balance between the Cu mobilized in the rhizosphere and the Cu absorbed by the plants. On the basis of the EF and TF values obtained (all <1), none of the species under study (Ruellia paniculata, Bidens pilosa, Pityrogramma calomelanos and Combretum leprosum) were classified as hyperaccumulators. However, consideration of readily bioavailable levels (extracted with MgCl2) and the rhizosphere soils (rather than total levels and bulk soils) yielded higher correlations with the levels of metal in plant tissues. This approach therefore appears more appropriate for determining the capacity of the plants to accumulate copper. The different characteristics of the bulk and rhizosphere soils have direct effects on the concentrations of copper, which were much lower in the rhizosphere soil. In general, each species responded differently to the high concentration of Cu in soils (range 3604–9601mgkg−1). By calculating the balance between the amounts of Cu mobilized in the rhizosphere and uptake by plants, we found that the presence of such plants in the field may have antagonistic effects. Two of the species (B. pilosa and P. calomelanos) contained more Cu in their tissues than mobilized in the rhizosphere. This is a desirable characteristic for restoration purposes, as the plants can reduce the bioavailable Cu content in soils and thus act as facilitators for regeneration of the site. By contrast, the other two species (R. paniculata and C. leprosum) mobilized more Cu in the rhizosphere than they were able to take up, which may led to transfer of bioavailable Cu to the ecosystem, which is undesirable in terms of site restoration.

Cellular and Subcellular Immunohistochemical Localization and Quantification of Cadmium Ions in Wheat (Triticum aestivum)

The distribution of metallic ions in plant tissues is associated with their toxicity and is important for understanding mechanisms of toxicity tolerance. A quantitative histochemical method can help advance knowledge of cellular and subcellular localization and distribution of heavy metals in plant tissues. An immunohistochemical (IHC) imaging method for cadmium ions (Cd2+) was developed for the first time for the wheat Triticum aestivum grown in Cd2+-fortified soils. Also, 1-(4-Isothiocyanobenzyl)-ethylenediamine-N,N,N,N-tetraacetic acid (ITCB-EDTA) was used to chelate the mobile Cd2+. The ITCB-EDTA/Cd2+ complex was fixed with proteins in situ via the isothiocyano group. A new Cd2+-EDTA specific monoclonal antibody, 4F3B6D9A1, was used to locate the Cd2+-EDTA protein complex. After staining, the fluorescence intensities of sections of Cd2+-positive roots were compared with those of Cd2+-negative roots under a laser confocal scanning microscope, and the location of colloidal gold particles was determined with a transmission electron microscope. The results enable quantification of the Cd2+ content in plant tissues and illustrate Cd2+ translocation and cellular and subcellular responses of T. aestivum to Cd2+ stress. Compared to the conventional metal-S coprecipitation histochemical method, this new IHC method is quantitative, more specific and has less background interference. The subcellular location of Cd2+ was also confirmed with energy-dispersive X-ray microanalysis. The IHC method is suitable for locating and quantifying Cd2+ in plant tissues and can be extended to other heavy metallic ions.

Testing the joint effects hypothesis of elemental defense using Spodoptera exigua.

Metal hyperaccumulation may be an elemental defense, in which high concentrations of a metal in plant tissues decrease herbivore survival or growth rate. The Joint Effects Hypothesis suggests that a combination of metals, or a combination of a metal with an organic compound, may have an enhanced defensive effect. The enhancement may be additive or synergistic: in either case the concentration of a particular metal necessary to provide a defensive benefit for the plant is lowered. We tested the Joint Effects Hypothesis using Spodoptera exigua (beet armyworm) neonates fed artificial diets. Metal + metal experiments utilized diets amended with metal pairs, using four metals commonly hyperaccumulated by plants (Co, Cu, Ni, and Zn). We also conducted metal + organic compound experiments, pairing each metal with nicotine, mustard seed powder, or tannic acid. We tested for joint effects using both lethal (LC20 levels) and sublethal concentrations (10-25% reduced larval weight) of the chemicals tested. For all experiments, either additive or synergistic effects were found. Of the metal + metal pairs tested, three (Co + Cu, Cu + Zn, and Ni + Zn) were synergistic in lethal concentration tests and only Co + Cu was synergistic in sublethal tests. For metal + organic combination lethal tests, synergism occurred for all combinations except for Co or Ni + nicotine, Ni + mustard seed powder, and Zn + nicotine. For sublethal tests, Zn + all three organic chemicals, Co + mustard seed powder or tannic acid, and Cu + nicotine, were synergistic. These results support the Joint Effects Hypothesis, suggesting that metals combined with other metals or organic compounds may be more effective against herbivores than individual metals.

Accumulation and Translocation of Heavy Metals by Amaranthus Retroflexus

Background: Phytoremediation is an ecofriendly method that recently used for contamination removal. Aim: n this article, phytoremediation of heavy metals (Cr, Cd, Cu, and Ni) by amaranth and Persian clover has been studied. Context: Soil samples with different amount of contamination were prepared. Contaminated soil samples keep in greenhouse and Amaranthus retroflexus cultivated in polypropylene pots. Before and after cultivation soil samples heavy metal amount has been analyzed. Result and Discussion: The amount of heavy metals in soils decreased after 120 days cultivation. Accumulations of heavy metals in plant tissues were measured. Translocation factor (TF) has been calculated. TF from root to upper part of plants in the order of Cr > Cu > Ni > Cd and TF from root to upper part of plants in the order of Ni > Cr > Cd > Cu. Amaranthus were resistance among high amount of heavy metal in soils. Result indicated that Amaranthus retroflexus has a good ability to remove heavy metal from contaminated soils. Conclusion: According to resultphytoremediation by Amaranthus retroflexus is a good and economical choice for remedy contaminated site.

The interaction of heavy metals and nutrients present in soil and native plants with arbuscular mycorrhizae on the riverside in the Matanza-Riachuelo River Basin (Argentina)

This study assessed the contamination by heavy metals (Cr, Cu, Pb, Zn), and nutrients (N, P) in soils and native plants, and the effect of the concentration of those elements with the density of arbuscular-mycorrhizal (AM) spores in soil and colonization in roots from the riverside of the Matanza-Riachuelo River Basin (MRRB). The concentration of metals and nutrients in soils and plants (Eleocharis montana, Cyperus eragrostis, Hydrocotyle bonariensis) increased from the upper sites (8km from headwaters) to the lower sites (6km from the mouth of the Riachuelo River) of the basin. AM-colonization on the roots of H. bonariensis and spore density in soil decreased as the concentrations of metals in soil and plant tissues increased from the upper to lower sites of the basin within a consistent gradient of contamination associated with land use, soil disturbance, population, and chemicals discharged into the streams and rivers along the MRRB. The general trends for all metals in plant tissue were to have highest concentrations in roots, then in rhizomes and lowest in aerial biomass. The translocation (TF) and bioconcentration (BCF) factors decreased in plants which grow from the upper sites to the lower sites of the basin. The plants tolerated a wide range in type and quantity of contamination along the basin by concentrating more metals and nutrients in roots than in aboveground tissue. The AM spore density in soil and colonization in roots of H. bonariensis decreased with the increase of the degree of contamination (Dc) in soil.

Increasing the Knowledge on the Management of Cu‐Contaminated Agricultural Soils by Cropping Tomato (Solanum Lycopersicum L.)

AbstractThis paper increases the knowledge on the potential use of Cu‐contaminated agricultural soils with tomato (Solanum lycopersicum L.). The effect of Cu and its interaction with soil properties on plant biomass production and on the accumulation of this metal in plant tissues were evaluated by conducting biomass assays in four representative Mediterranean agricultural soils contaminated by Cu. Copper toxicity on plant biomass production, evaluated through the effective concentrations of Cu added to soil that reduce the biomass production by 50% (EC50) and by 10% (EC10), was higher in soils having less soil organic matter and clay content and even in soils with favourable properties but having salinity. For the cases in which tomato was collected, Cu concentrations in them were similar for all soils and doses and never exceed the maximum Cu concentration allowed by the Codex Alimentarius Commission Regulation (10 mgCu kg−1 in fresh weight basis). According to our results, tomato could be cropped in Cu‐contaminated Mediterranean agricultural soils when concentrations of Cu determined in them rely between their respective EC50 and EC10, because production and quality of fruits, the latter understood as the Cu concentration in them, would not be compromised. For the soils assayed, these values would range between 32·9 and 1696·5 mg kg−1, depending on soil properties. Because the baseline value considered is similar to those established in other parts of the European Mediterranean region, these results can be used as guidance for this region to establish adequate phytoremediation strategies and prevent land degradation processes. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Redistribution of elements of metals in plant tissues under treatment by non-ionic colloidal solution of biogenic metal nanoparticles.

The content of metal elements in plant tissues of 10-day wheat seedlings after seed pre-treatment and foliar treatment with non-ionic colloidal solution of metal nanoparticles (Fe, Mn, Cu, Zn) was determined by an atomic absorption spectrometer. It was shown that metal nanoparticles due to their physical properties (nanoscale and uncharged state) were capable of penetrating rapidly into plant cells and optimizing plant metabolic processes at the early stages of growth and development.

Phytoremediation of heavy metals (Cd, Pb and V) in gas refinery wastewater using common reed (Phragmitis australis)

Industrial wastewaters are of the major sources of heavy metal pollution in the environment. In the Middle East, gas and oil industry is the major source of heavy metal pollution and releases significant amounts of metals into the terrestrial and aquatic environment. In this research the capability of the common reed ( Phragmitis australis ) in absorbing heavy metals Cd, Pb and V from the wastewater of a gas refinery plant in Iran was investigated. The plant samples were collected from the vicinity of the Bidboland gas refinery plant in Iran and were used for the treatment of wastewaters collected from the outflow of the refinery plant. The metal concentrations were measured in the roots of the plant species before treatment and after 2, 6 and 10 days of treatment procedure. The heavy metal concentrations were measured after acid digestion and using an ICP-OES instrument. After 10 days of treatment, the concentrations of the metals in plant tissues increased by 2.5, 6.9 and 2.7 times for Cd, Pb and V, respectively. The best treatment time was suggested to be 6 days. The common reed was observed to have a very good capability in removing heavy metals from the gas refinery wastewater.

Heavy Metal Contamination of Herbal Drugs: Implication for Human Health-A Review

Interest in the use of medicinal plants in treatment of diseases in Africa has increased tremendously over the past decade. Ingestion of contaminated medicinal plants and herbal medicinal products is regarded as potential source of heavy metal toxicity to both man and animals. Heavy metals are often not well defined in medicine, but include all toxic metals. They are released into the environment by both natural and a variety of anthropogenic sources. The presence of heavy metals in plant tissues is primarily dependent upon their availability and concentration in the soil. They can also be deposited directly on plant surfaces from the atmosphere. Heavy metals are persistent in nature due to their long biological half-life. The major heavy metals of health concern are arsenic, cadmium, lead and mercury. They are the redox inactive metals and show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione - an antioxidant. In order to ensure quality and safety of herbal drugs, cultivation and collection of medicinal plants in the immediate vicinity of industrial sites which utilize these metals and their compounds, and sites where these metals have been improperly disposed is highly discouraged; because plants from these areas are prone to high concentration of heavy metals, hence, increases human risk of contamination when taken. In addition,

Effect of EDTA and DTPA on Phytoremediation of Pb-Zn Contaminated Soils by Eucalyptus camaldulensis Dehnh and Effect on Treatment Time

In this research a pot experiment was carried out to investigate the remediation ability of E. camaldulensis Dehnh in Lead-Zinc (Pb-Zn) contaminated soil. The study also investigated the effects of ethylenediaminetetraacetic acid (EDTA) and diethylenetrinitrilopentaacetic acid (DTPA) on the phytoremediation efficiency of the plant species, and harvest time as a suitable dose of chelating agents was considered. When the plants had grown for 30 days, the seedlings were harvested to determine the concentration of metals in plant tissues and soil. In general, Pb level decreased in the order of: shoot > soil > root, whilst Zn content decreased in the sequence shoot > root > soil. As a second step, contaminated soils were treated with EDTA (1.5, 3, 6, 9mmolkg -1 ) and DTPA (1.5, 3, 6, 9mmolkg -1 ). The results demonstrated that chelating agents enhance metal content in E. camaldulensis. The greatest bioconcentration factor in EDTA treatments (3.94) was observed in 9EDTA treatment followed by 6EDTA treatment (3.41). Similarly this was observed for 9DTPA (2.30) and 6DTPA (2.23) respectively. With respect to non-significant difference between 9EDTA and 6EDTA treatments and between 6DTPA and 9DTPA, low doses (6mmolkg -1 ) were used in the third step for the highest heavy metal uptake over 30, 60 and 90 days. Results reveal that the concentration of metal soil solution decreases gradually with the passage of time. The results indicate that E. camaldulensis has the potential for the phytoextraction of metal-contaminated soils but should not be used unless the biomass containing such accumulated metals is removed for disposal. Significant improvement over current chelate-assisted phytoextraction of metals may be possible but should be implemented cautiously because of the environmental risks.

Adaptation of plants to an environment polluted with heavy metals

This paper presents the problem of tolerance of plants to heavy metals. Induction, development and stability of tolerance are described. Multiple and co-tolerance are presented in the context of specificity of acquired tolerance to heavy metals. Phenomena involved in the uptake and distribution of metals in plant tissues along with the mechanisms of exclusion and accumulation are discussed. The problem of tolerance development in plants is presented also in the light of the nutritional conditions that plants most often encounter in contaminated environments.

Elemental distribution in reproductive and neural organs of the Epilachna nylanderi (Coleoptera: Coccinellidae), a phytophage of nickel hyperaccumulator Berkheya coddii (Asterales: Asteraceae) by micro-PIXE.

The phenomenon of metal hyperaccumulation by plants is often explained by a pathogen or herbivore defense hypothesis. However, some insects feeding on metal hyperaccumulating plants are adapted to the high level of metals in plant tissues. Former studies on species that feed on the leaves of Berkheya coddii Roessler 1958 (Asteraceae), a nickel-hyperaccumulating plant, demonstrated several protective mechanisms involved in internal distribution, immobilization, and elimination of Ni from the midgut and Malpighian tubules. These species are mainly coleopterans, including the lady beetle, Epilachna nylanderi (Mulsant 1850) (Coleoptera: Coccinellidae), collected from the ultramafic ecosystem near Barberton in South Africa. By performing particle-induced X-ray emission microanalysis elemental microanalysis (PIXE), this study examined whether Ni may be harmful to internal body systems that decide on insect reactivity (central nervous system [CNS]), their reproduction, and the relationships between Ni and other micronutrients. Data on elemental distribution of nine selected elements in target organs of E. nylanderi were compared with the existing data for other insect species adapted to the excess of metals. Micro-PIXE maps of seven regions of the CNS showed Ni mainly in the neural connectives, while cerebral ganglia were better protected. Concentrations of other bivalent metals were lower than those of Ni. Testis, compared with other reproductive organs, showed low amounts of Ni. Zn was effectively regulated at physiological dietary levels. In insects exposed to excess dietary Zn, it was also accumulated in the reproductive organs. Comparison of E. nylanderii with other insects that ingest hyperaccumulating plants, especially chrysomelid Chrysolina clathrata (Clark) (Coleoptera: Chrysomelidae), showed lower protection of the CNS and reproductive organs.

Biometric and biochemical attributes of alfalfa seedlings as indicators of stress induced by excessive cadmium

Abstract The biometric and biochemical attributes of alfalfa ( Medicago sativa L.) seedlings were studied after their exposure to 0-120 μM cadmium for 28 days using hydroponic culture. The growth, photosynthetic area and pigment contents (chlorophyll a, b and total) declined significantly ( p ≤ 0.05) in the presence of high cadmium concentrations (90 and 120 μM). A steady increase in lipid peroxidation assessed via MDA production was observed with increasing levels of cadmium. Cadmium uptake by the plant tissues was concentration dependent. The roots accumulated 1020 µg g-1 of cadmium which was two folds than leaves. An enhanced production up to 600 µg g -1 of proline was observed at higher levels of cadmium. Though, cadmium toxicity was expressed in terms of decline in growth variables, chlorophyll content and oxidative damage but restricted transfer of the metal to the aerial tissue and greater production of proline in response to higher metal content seems to alleviate cadmium toxicity. Thus, ability of alfalfa plants to tolerate high cadmium concentrations can be a manifestation of effective defensive mechanism derived from differential accumulation of metal in plant tissues in addition to enhanced production of proline.