植物生长抑制剂对万寿菊镉积累和化学形态的影响

通过水培实验研究了细胞分裂抑制剂（青鲜素 MH）和蛋白合成抑制剂（放线菌酮 CHI）对万寿菊镉积累及化学形态的影响。结果表明,在溶液Cd浓度为0.1 mg·L^-1的条件下,投加浓度为2、4 mmol·L^-1青鲜素及3、6 μmol·L^-1放线菌酮显著抑制了万寿菊的相对生长速率及地上部镉含量,另外两种抑制剂也降低了万寿菊地上部可溶性蛋白含量,但对叶绿素a、b及总叶绿素含量并无显著影响,证明细胞分裂及蛋白合成过程直接影响着万寿菊地上部镉积累。通过采用逐步提取法对万寿菊体内镉的化学存在形态分析,表明在单独Cd处理条件下万寿菊体内移动性较差的醋酸提取态及NaCl提取态镉占有较高比例,其中地上部两种结合态镉约占万寿菊地上部总镉量的68%,而施加植物生长抑制剂后万寿菊地上部两种结合态镉含量显著降低,放线菌酮处理下仅为31%,进一步证实镉主要与万寿菊体内蛋白质等物质结合后才能在其体内长久固定,否则不能在其体内发生累积。     

Role of Sulfur in Cadmium Accumulation of Tagetes erecta L.

The role of sulfur in cadmium (Cd) accumulation was investigated in Tagetes erecta L. Shoot Cd concentrations were significantly increased with increasing of sulfur levels in the culture solution. In another experiment, leaf application of sodium sulfate (Na₂SO₄) or cysteine to sulfur (S)-starved plants significantly increased Cd accumulation in shoots up to three folds or twice that of those S-starved plants. When plants were cultured at 35°C, shoot Cd accumulation was significantly lower than in those cultured at 25°C, however, leaf application of glutathione or cysteine significantly increased Cd accumulations in shoots than that of no application. It is suggested that elevated temperature (35°C) might disturb sulfur assimilation, for example, cysteine and glutathione synthesis, thus reducing Cd accumulation. This phenomenon can be alleviated by adding thiol-containing compounds, such as cysteine and glutathione, but not by adding Na₂SO₄. These results indicate that thiol-containing compounds play an important role in Cd accumulation of T. erecta.     

铅锌矿区分离丛枝菌根真菌对万寿菊生长与吸镉的影响

盆栽试验研究了土壤不同施Cd水平(0、20、50 mg kg-1)下,接种矿区污染土壤中丛枝菌根真菌对万寿菊根系侵染率、植株生物量及Cd吸收与分配的影响。结果表明:接种丛枝菌根真菌显著提高了Cd胁迫下万寿菊的根系侵染率和植株生物量;随着施Cd水平提高,各处理植株Cd浓度和Cd吸收量显著增加。各施Cd水平下万寿菊地上部Cd吸收量远远高于根系Cd吸收量,尤其在20 mg kg-1施Cd水平下,接种处理地上部Cd吸收量是根系的3.90倍,对照处理地上部Cd吸收量是根系的2.33倍;同一施Cd水平下接种处理地上部Cd吸收量要显著高于对照。总体上,试验条件下污染土壤中分离的丛枝菌根真菌促进了万寿菊对土壤中Cd的吸收,并增加了Cd向地上部分的运转,表现出植物提取的应用潜力。     

Characterization of Enterobacter intermedius MH8b and its use for the enhancement of heavy metals uptake by Sinapis alba L.

The aim of this study was to test whether the multiple-tolerant bacterium Enterobacter intermedius MH8b isolated from metal-contaminated soil is able to promote plant growth and enhance Zn, Cd and Cu uptake by Sinapis alba L. under laboratory conditions. Additionally, the mechanisms of the plant growth promotion and the ecological consequences of bioaugmentation were examined. MH8b exhibited the ability to produce 1-amino-cyclopropane-1-carboxylic acid deaminase, indole 3-acetic acid and hydrocyanic acid and was also able to solubilize inorganic phosphate. Soil inoculation with MH8b significantly increased plant biomass as well as the accumulation of Zn (32%) and Cd (94%) in plant shoots. DGGE and PLFA analysis revealed that the introduced MH8b had only a short-term influence on the structure of indigenous microbial communities. The plant growth-promoting properties of MH8b and its ability to increase the metal uptake connected with its long-term survival and its short-term impact on autochthonous microflora make the strain a good candidate for the promotion of plant growth and phytoremediation efficiency.     

Influence of Cadmium Toxicity on Growth and Antioxidant Enzyme Activity in Rice Cultivars with Different Grain Cadmium Accumulation

Abstract

The effect of cadmium (Cd) toxicity on growth, lipid peroxidation, and antioxidant enzymes was studied using two rice cultivars, Bing 97252 with low and Xiushui 63 with high grain Cd accumulation. Plants were exposed to 0–5 μ M Cd in hydroponic culture. Cadmium stress inhibited plant height and chlorophyll content and altered melondialdehyde (MDA) content and the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Roots and shoots responded differently to Cd in terms of antioxidant enzyme activity. Generally, the activities of SOD, POD, and CAT decreased with increase in Cd level, while the activity of MDA increased with increase in Cd level. With the increase in Cd concentration in nutrient solution, MDA content in shoots and roots of Xiushui 63 increased at a much higher rate than did that of Bing 97252 at both growth stages. At booting stage, a decrease of 46%–52% in SOD activity was noted in plant roots grown under 5 μ M Cd, while at tillering stage the decrease was 13%–19% compared with the control. A significant decrease in chlorophyll content and plant height was noted under higher Cd treatment (1.0 and 5.0 μ mol) at two stages. The higher MDA and lower chlorophyll content in the cultivar Xiushui 63 showed that it is more sensitive to Cd than the cultivar Bing 97252.     

Interactive Effects of Lanthanum and Cadmium on Plant Growth and Mineral Element Uptake in Crisped-Leaf Mustard Under Hydroponic Conditions

Plant growth and mineral element accumulation in Brassica juncea var. crispifolia (crisped-leaf mustard) under exposure to lanthanum (La) and cadmium (Cd) were studied by employing a hydroponic experiment with a complete two-factorial design. Four levels of La (0.05–5.0 mg L^?1) and two levels of Cd (1.0 and 10.0 mg L^?1) were used in this experiment. Lanthanum did not improve plant growth in this experiment. Addition of La (≥ 1.0 mg L^?1) or Cd (≥ 10 mg L^?1) to the solution inhibited root elongation. Lanthanum treatments reduced accumulations of iron (Fe), manganese (Mn), and zinc (Zn) in roots, and Mn in shoots. Lanthanum at ≥ 1.0 mg L^?1 limited the Cd translocation from roots to shoots and thus decreased the accumulation of Cd in shoots. Cadmium had no influence on La accumulations in roots, but inhibited the accumulation of La in shoots. The study results suggest that applications of rare earth elements in vegetables would be potentially risky to human health.     

Growth and cadmium accumulation in two durum wheat cultivars

Abstract

A solution culture study was conducted to determine the effects of cadmium (Cd) application on Cd accumulation and growth of two durum wheat (Triticum turgidum L. var durum) cultivars. Arcola and DT618 were grown in nutrient solution for 13 days. Cadmium application to nutrient solution significantly (P ≤ 0.05) decreased root and shoot biomass, leaf area, leaf mass, total root length, and chlorophyll a and b concentration of the first leaf. The deleterious effects of Cd on plant growth were explained by a modified version of Weibull distribution function of the form, y = a.exp(b.√Cd), where ‘y’ is the growth parameter, ‘a’ is plant growth in the absence of Cd, and ‘b’ is reduction in growth with per unit increase in solution Cd. Total root length was decreased the most (80%) and chlorophyll b concentration of the first leaf decreased the least (9%) with per unit increase in solution Cd. Although the two cultivars were significantly different in some growth characteristics, both responded similarly to increase of Cd concentration in solution. Cadmium concentration in roots and shoots increased significantly (P ≤ 0.05) with Cd application, but due to concomitant decrease in growth the Cd content of plants remained constant at solution Cd concentrations of 5 μm or above. We concluded that seedlings of durum cultivars with different growth potential responded similarly to Cd application in nutrient solution.     

丛枝菌根真菌对万寿菊生长、吸镉及生理特性的影响

A pot experiment was carried out to study the effects of three arbuscular mycorrhizal fungi (AMF), including Glomus intraradices, Glomus constrictum and Glomus mosseae, on the growth, root colonization and Cd accumulation of marigold (Tagetes erecta L.) at Cd addition levels of 0, 5 and 50 mg kg-1 in soil. The physiological characteristics, such as chlorophyll content, soluble sugar content, soluble protein content and antioxidant enzyme activity, of Tagetes erecta L. were also investigated. The symbiotic relationship between the marigold plant and arbuscular mycorrhizal fungi was well established under Cd stress. The symbiotic relationship was reffected by the better physiobiochemical parameters of the marigold plants inoculated with the three AMF isolates where the colonization rates in the roots were between 34.3% and 88.8%. Compared with the non-inoculated marigold plants, the shoot and root biomass of the inoculated marigold plants increased by 15.2%- 47.5% and 47.8%-130.1%, respectively, and the Cd concentration and accumulation decreased. The chlorophyll and soluble sugar contents in the mycorrhizal marigold plants increased with Cd addition, indicating that AMF inoculation helped the marigold plants to grow by resisting Cd stress. The antioxidant enzymes reacted differently with the three AMF under Cd stress. For plants inoculated with G. constrictum and G. mosseae, the activities of superoxide dismutase (SOD) and catalase (CAT) increased with increasing Cd addition, but peroxidase (POD) activity decreased with increasing Cd addition. For plants inoculated with G. intraradices, three of the antioxidant enzyme activities were significantly decreased at high levels of Cd addition. Overall, the activities of the three antioxidant enzymes in the plants inoculated with AMF were higher than those of the plants without AMF inoculation under Cd stress. Our results support the view that antioxidant enzymes have a great influence on the biomass of plants, and AMF can improve the capability of reactive oxygen species (ROS) scavenging and reduce Cd concentration in plants to alleviate Tagetes erecta L. from Cd stress.     

Alleviation of cadmium phytotoxicity by magnesium in Japanese mustard spinach

Abstract

To clarify the mechanism of Magnesium (Mg) in alleviating cadmium (Cd) phytotoxicity, Japanese mustard spinach (Brassica rapa L. var. pervirdis) was grown for 10 days after treatment in hydroponics in a growth chamber under natural light. The treatments were: (1) nutrient solution alone (Control), (2) 10 mmol L^?1 Mg (High-Mg), (3) 2.5 µmol L^?1 Cd (Cd-toxic), (4) 2.5 µmol L^?1 Cd plus 10 mmol L^?1 Mg (Mg-alleviated). The Cd-toxic treatment showed substantial growth retardation and chlorosis of young leaves, such symptoms were not observed in Mg-alleviated plants. Magnesium-alleviated plants showed higher shoot growth, more than twofold, and decreased shoot Cd concentration, approximately 40%, compared with Cd-toxic plants. This increase in shoot growth and simultaneous decrease in shoot Cd concentration may explain the alleviation of Cd toxicity with Mg in Japanese mustard spinach. In Cd-toxic plants, concentrations of K in shoots and Zn in both shoots and roots increased compared with the other three treatments. Concentrations and accumulations of Fe and Mn in shoots decreased significantly in the Cd-treated (Cd-toxic and Mg-alleviated) plants compared with the control and High-Mg plants. Thus, the application of high amounts of Mg in the nutrient solution can alleviate Cd toxicity in plants.     

Accumulation and Toxicity of Germanium in Cucumber under Different Types of Germaniums

The effects of germanium dioxide (GeO₂) and 2-carboxyethyl germanium sesquioxide (Ge-132) treatments on cucumber (Cucumis sativus L.) growth and Ge accumulation and toxicity were investigated. Accumulated Ge contents in plant treated with GeO₂ were two times greater than that in plants treated with Ge-132. Germanium accumulated primarily in the shoots in the GeO₂ treatments and in the roots in the Ge-132 treatments. In contrast GeO₂ was easily transported from roots to shoots. In cucumber fruit, the range of Ge content in both the GeO₂ and Ge-132 treatments was in the order of stalk > rind > pulp > seeds, suggesting that Ge accumulation was based on distance from xylem. Silicon (Si) content significantly decreased as GeO₂ concentration increased, but there was no difference in Si content in the Ge-132 treatment. Therefore, plant growth and Ge accumulation are affected differently by GeO₂ and Ge-132 treatments, based partly on treatment concentrations.     

Uptake,distribution, and binding of cadmium and nickel in different plant species

For better understanding of mechanisms responsible for differences in uptake and distribution of cadmium (Cd) and nickel (Ni) in different plant species, nutrient solution experiments were conducted with four plant species [bean (Phaseolus vulgaris L.), rice (Oryza saliva L.), curly kale (Brassica oleracea L.) and maize (Zea mays L.)]. The plants were grown in a complete nutrient solution with additional 0.125 and 0.50 μM Cd or 0.50 and 1.00 μM Ni. Large differences in Cd and Ni concentrations in shoot dry matter were found between plant species. Maize had the highest Cd concentration in the shoots, and bean the lowest. Contrary to Cd, the Ni concentrations were highest in the shoots of bean and the lowest in maize. A gradient of Cd concentrations occurred in bean and rice plants with the order roots > > stalk base >> shoots (stems/sheaths > leaves). A similar gradient of Ni concentrations was also found in maize and rice plants. In the xylem sap, the Cd and Ni concentrations were positively correlated with Cd and Ni concentrations in the shoot dry matter. In the roots of maize, about 60% of Cd could be extracted with Tris‐HCl buffer (pH 8.0), while in roots of other plant species this proportion was much lower. This higher extractability of Cd in the roots of maize is in accordance with the higher mobility as indicated by the higher translocation of Cd from roots to shoots and also the higher Cd concentrations in the xylem sap in maize than in the other plant species. Similarly, a higher proportion of Ni in the soluble fraction was found in the roots of bean compared with maize which is in agreement with the higher Ni accumulation in the shoots of bean. The results of gel‐filtration of the soluble extracts of the roots indicated that phytochelatins (PCs) were induced in the roots upon Cd but not Ni exposure. The higher Cd concentrations and proportions of Cd bound to PC complexes in the roots of maize compared with the other plant species suggest that PCs may be involved in the Cd trans‐location from roots to shoots.     

EFFECT OF CADMIUM ON PHYSIOLOGICAL RESPONSES OF WHEAT AND CORN TO IRON DEFICIENCY

This work evaluated the effect of cadmium (Cd) on the physiological responses of corn (Zea Mays L.) and wheat (Triticum aestivum L.) to iron (Fe) deficiency. For this purpose, seedlings of corn and wheat were cultivated under controlled conditions, plants were grown in different strength Hoagland's solutions for one month. In the fifth week, some seedlings were still in full strength Hoagland's solution (+Fe) and others were in full strength Hoagland's solutions without iron (?Fe). The plants were exposed to different cadmium (Cd) concentrations for four days. The plant chlorophyll content of young leaves, Fe and Cd content in shoots and roots, biomass production, and phytosiderophores (PS) release by roots were assessed. Results showed that Cd decreased the chlorophyll content of young leaves, accompanied by a significant shoot and root biomass reduction for Fe-deficient and Fe-sufficient wheat and corn across all Cd treatments. However, chlorophyll content and shoot and root biomass of Fe-deficient wheat and corn were lower than Fe-sufficient plants at different Cd concentrations. Iron-deficiency induced Cd accumulation compared to Fe-sufficient in wheat and corn; however, a depressive effect of Cd on iron acquisition in shoots and roots of Fe-deficient and Fe-sufficient wheat and corn across all Cd treatments was observed. Cadmium also inhibited PS release in Fe-deficient and Fe-sufficient wheat and corn. Iron-deficient PS release was higher than Fe-sufficient corn and wheat across all Cd treatments. These results suggested that Cd might reduce capacity of plants to acquire iron from solution by inhibiting PS release.     

Effect of elevated atmospheric CO2 concentration on growth and physiology of wheat and sorghum under cadmium stress

ABSTRACT

Elevated concentrations of carbon dioxide (e[CO₂]) affect plant growth and physiological characteristics, including metal accumulation, and the activity of anti-oxidant enzymes. These effects were investigated in cadmium (Cd) tolerant wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor (L.) Moench.) cultivars. Plants were grown at the ambient and elevated CO₂ levels, with four concentrations of Cd (0, 10, 20 and 40 mg kg^?1) added to the soil. After 60 days, subsamples were tested for chlorophylls and carotenoids, protein, enzyme activities and morphological characteristics.

Results showed that e[CO₂] increased plant height, leaf area, and the dry weight of shoots and roots (P < 0.01). In addition, it decreased the Cd concentration in the shoots and roots of wheat, and increased the same concentrations for sorghum. With increasing Cd, the activities of the anti-oxidants, SOD and GSH-px increased in wheat. The differences in enzyme activity parallel the changes in Cd concentration in the plants of both species.     

Cadmium accumulation and distribution in sunflower plant

Cadmium (Cd) accumulation and distribution was studied in sunflower (Helianthus annuus L., public line HA‐89) plant. From an uncontaminated sandy loam brown forest soil with 162 μg kg^‐1 HNO₃/H₂O₂ extractable Cd the HA‐89 sunflower public line accumulated 114 ug kg^‐1 Cd in its kernels under open field conditions. This value is rather low as compared to data found by others. Sandy loam brown forest soil was treated with 0, 1 or 10 mg kg^‐1 of Cd to study the interaction of this heavy metal with young sunflower plants in a greenhouse pot experiment. The fresh weight and dry matter accumulation of sunflower plant organs (roots, shoots, leaves or heads) was unaffected by cadmium treatment of soil. The nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), or zinc (Zn) uptake of sunflower plant organs was not influenced by lower or higher Cd‐doses, except sunflower heads where 10 mg kg^‐1 of Cd treatment of soil significantly reduced the uptake of Ca, Fe, and Mn. Although Cd reduced the Zn uptake of roots, its rate was statistically not significant. Cadmium was accumulated prevalently in roots (1.21 mg kg^‐1,4.97 mg kg^‐1, or 13.69 mg kg^‐1 depending on Cd‐dose), and its concentration increased also in shoots or leaves. In spite of the short interaction time, elevated concentrations of cadmium (0.78 mg kg^‐1, 1.34 mg kg^‐1, or 3.02 mg kg^‐1 depending on Cd‐dose) were detected in just emerged generative organs (heads) of young sunflower plants.     

Cadmium‐induced changes in glutathione and phenolics of Thlaspi and Noccaea species differing in Cd accumulation

Glutathione (GSH) and phenolics play an important role in plant defense against metal‐ion toxicity. The antioxidant activity and metal‐binding capacity of these compounds can account for the protective effects. In contrast to animal‐cell models, however, the possible interplay among these substances in stress defense of plants is poorly investigated. This study compares the influence of cadmium (Cd) on the profiles of both soluble phenolics and GSH in shoots of different Thlaspi and Noccaea species: two ecotypes of the nonhyperaccumulator T. arvense differing in Cd resistance (ecotype Aigues Vives, Cd‐sensitive, and ecotype Jena, Cd‐resistant) and two Cd‐tolerant Cd‐Zn hyperaccumulators N. praecox and N. caerulescens (formerly Thlaspi praecox and T. caerulescens). To reveal the possible influence of Cd‐induced sulfur (S) shortage on the stress response, plants receiving normal S concentrations (500 μM MgSO₄) and plants treated with surplus S (500 μM MgSO₄ + 500 μM K₂SO₄) were analyzed. Our working hypothesis was that species differences in tolerance to high tissue Cd concentrations should be reflected by differences in endogenous levels of GSH and phenolic compounds. The results reveal clear species‐dependent differences in both the constitutive patterns and the Cd‐ and S‐induced changes in shoot concentrations of GSH and phenolics. However, no simple relationship between these shoot concentrations and Cd accumulation and tolerance can be established.     

Cadmium Uptake by Lettuce in Fields Treated with Cadmium‐Spiked Phosphorus Fertilizers

The rate of cadmium (Cd) uptake by lettuce (Lactuca savita var. longifolia) over an entire growing season was investigated in a field treated with phosphorus (P) fertilizers spiked to different Cd levels. Romaine lettuce was planted following the standard cultivation practices. Over the growing period, soil and plant samples were taken to determine the total soil Cd content, Cd concentration of 1:0.5 (soil‐to‐water) extracts, and Cd content of plant tissue. Results indicated that lettuce can accumulate as much as 20 mg Cd per kilogram dry biomass without adverse effects on growth. The Cd content in the plant tissues decreased exponentially with time, indicating a dilution factor existing along with the plant growth. The plant uptake rate on a per‐unit‐area basis increased over time and can be simulated by a sigmoid pattern model. The plant uptake coefficient (α, L solution kg biomass^?1 day^?1) decreased as the Cd treatment level increased.     

Cadmium Uptake by Winter Wheat Seedlings in Response to Interactions Between Phosphorus and Zinc Supply in Soils

ABSTRACT

Effects of application of zinc (Zn) (0, 1, 5, 10 mg kg^?1 soil) and phosphorus (P) (0, 10, 50, 100 mg kg^?1 soil) on growth and cadmium (Cd) accumulations in shoots and roots of winter wheat (Triticum aestivum L.) seedlings were investigated in a pot experiment. All soils were supplied with a constant concentration of Cd (6 mg kg^?1 soil). Phosphorus application resulted in a pronounced increase in shoot and root biomass. Effects of Zn on plant growth were not as marked as those of P. High Zn (10 mg kg^?1) decreased the biomass of both shoots and roots; this result may be ascribed to Zn toxicity. Phosphorus and Zn showed complicated interactions in uptake by plants within the ranges of P and Zn levels used. Cadmium in shoots decreased significantly with increasing Zn (P < 0.001) except at P addition of 10 mg kg^?1. In contrast, root Cd concentrations increased significantly except at Zn addition of 5 mg kg^?1 (P < 0.001). These results indicated that Zn might inhibit Cd translocation from roots to shoots. Cadmium concentrations increased in shoots (P < 0.001) but decreased in roots (P < 0.001) with increasing P supply. The interactions between Zn and P had a significant effect on Cd accumulation in both shoots (p = 0.002) and roots (P < 0.001).     

Isolation and identification of rapeseed (Brassica napus) cultivars for potential higher and lower Cd accumulation

Cadmium (Cd) as a non‐essential toxic metal has become one of the seriously environmental problems. Overload of Cd into plant shoots, particularly the addible parts (i.e., grains), jeopardizes crop production and food safety. Isolating and identifying genotypic variations in Cd accumulation of rapeseed (Brassica napus) cultivars is an efficient approach for phytoremediation and developing lower Cd‐accumulating plants. In this study, a trial was conducted under natural condition in Nanjing, China, from 2014 to 2017, and identified 64 rapeseed cultivars collected from the areas of Gui Zhou province. Rapeseed grew under moderate Cd exposure (5 mg kg^?1) for 5 months, and shoots were harvested for Cd quantification. A great variation of total Cd concentrations in shoots, ranking from 0.16 to 17.03 mg Cd kg^?1, was found. Following the initial examination of all cultivars, two sets of plants with high (#138 and #177) and low (#208 and #244) Cd concentrations were further investigated. Throughout the growth period, cultivars #138 and #177 accumulated more Cd during vegetative (30, 60, and 120 d) and late developmental (180 d) stages than cultivars #208 and #244. The higher Cd concentration in shoots of #138 and #177 was associated with the higher Cd concentration in xylem sap, suggesting the greater capability of Cd translocation from roots to shoots. Compared to #208 and #244, Cd exposure moderately reduced zinc and iron concentrations in some tissues of #138 and #177, whereas the manganese and magnesium concentrations showed no change. Although #138 and #177 cultivars accumulated more Cd in their shoots, no Cd toxicity was detected. Moreover, both #138 and #177 cultivars had a similar biomass to #208 or #244. These results suggest that #138 and #177 rapeseeds are tolerant to Cd stress.     

SALINITY-HEAVY METAL INTERACTIONS IN FOUR SALT-TOLERANT PLANT SPECIES

The concurrent effect of NaCl salinity and heavy metals [cadmium (Cd), chromium (Cr) and nickel (Ni)] on growth, sodium (Na), and heavy metal accumulation was assessed in four salt tolerant plant species. These were: barley (Hordeum vulgare L.), purslane (Portulaca oleracea L.), Inula crithmoides L., and Plantago coronopus L., all of which have documented potential for use in saline agriculture. Plants were grown in perlite and irrigated with salinized and non-salinized nutrient solutions (9 dS m^?1 and 18 dS m^?1) containing 2 ppm Cd, 4 ppm Cr, 10 ppm Ni, and a non-metal control. Salinity, Cd, and Ni caused a significant decrease in the dry biomass accumulation of P. oleracea, but had no effects on other plant species. Sodium accumulation was highest in P. coronopus and I. crithmoides, indicating pronounced halophytic properties. The presence of heavy metals reduced Na accumulation in H. vulgare and P. oleracea, but had no effect on P. coronopus and I. crithmoides, indicating that the Na-heavy metal interaction is plant-specific. Metal accumulation in the four plant species was generally enhanced by the 9 dS m^?1 treatment, but not by the 18 dS m^?1 treatment. This could indicate the presence of an ionic exclusion mechanism operating at high salinity levels that would operate indiscriminately on Na as well as on Cd, Cr, and Ni     

Relative toxicity of cadmium,lead, and zinc on barley

Abstract

The relative toxicity of cadmium (Cd), lead (Pb), and zinc (Zn) on the growth performance of barley (Hordeum vulgare L.) was measured. Lead and Zn resulted in an increase in dry matter production at the lower additions. All the Cd and the higher Pb and Zn additions resulted in significant decreases in growth over the controls, the roots showing a greater decrease in dry matter accumulation than did shoots. Roots accumulated higher amounts of Cd, Pb, and Zn in direct proportion to that soil‐applied. A significant inverse relationship between relative yield and tissue element concentration was observed. Toxicity occurred in the following order: Cd > Pb > Zn. Threshold concentration, critical tissue concentrations, and loading rates to produce a 10% yield reduction were also calculated. Our study indicates the possibility of estimating barley yield based on plant tissue Cd, Pb, and Zn concentrations.