Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

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.     

Use of reactive phosphate rocks as fertilizer on acid upland soils in Indonesia: accumulation of cadmium and zinc in soils and shoots of maize plants

A pot experiment was conducted to study the contribution of reactive phosphate rocks (RPRs) on the accumulation of Cd and Zn in 10 acid upland soils in Indonesia and shoots of Zea mays plants grown on these soils. Two types of RPR were used at a rate of 0.5 g (kg soil)^–1: RPRL containing 4 mg Cd kg^–1 and 224 mg Zn kg^–1, and RPRH containing 69 mg Cd kg^–1 and 745 mg Zn kg^–1. Zea mays was harvested at 6 weeks after planting. The application of RPRH significantly increased the concentrations of Cd in the shoots. The application of this RPR also increased the amount of Cd which could be extracted by 0.5 M NH₄‐acetate + 0.02 M EDTA pH 4.65 from the soils. More than 90% of the added Cd remained in the soil. As Zn is an essential element and the studied acid upland soils are Zn‐deficient, increased plant growth upon RPR application might be partly attributed to Zn present in the phosphate rock. However, more experiments are needed to confirm this hypothesis. The Cd and Zn concentrations and CEC of the soils were important soil factors influencing the concentrations of Cd and Zn in the shoots of maize plants grown on these soils.     

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).     

河北板蓝根产地土壤-植物中镉铅汞砷含量特征及其污染评价

采用野外调查和室内分析相结合的方法,研究了河北省安国市和蔚县板蓝根产地土壤-植物中Cd、Pb、Hg、As含量特征及其在菘蓝中的累积特性,并对板蓝根产地土壤和草药中Cd、Pb、Hg、As污染状况进行了评价,为该地区安全、合理地发展中草药生产提供数据支撑和科学依据。结果表明,安国市和蔚县板蓝根产地土壤中重金属Cd、Pb、Hg、As含量差异不大,土壤重金属含量的变异系数在11.70%~97.65%。以《土壤环境质量标准》(GB 15618—1995)一级标准值进行评价,综合污染指数评价结果显示45%板蓝根种植区土壤Cd、Pb、Hg、As污染等级为警戒限,其他处于清洁水平;而以《土壤环境质量标准》二级标准值进行评价,种植区单项污染指数及综合污染指数结果均0.7,土壤环境清洁。此外,菘蓝地上部(大青叶)Cd、Pb、Hg、As平均含量分别为0.22 mg·kg~(-1)、0.89 mg·kg~(-1)、0.04 mg·kg~(-1)、0.25 mg·kg~(-1),对重金属的富集能力表现为CdHgPbAs;菘蓝地下部(板蓝根)Cd、Pb、Hg、As含量均值分别为0.14 mg·kg~(-1)、0.57 mg·kg~(-1)、0.04 mg·kg~(-1)、0.26 mg·kg~(-1),对重金属的富集能力表现为CdHgAsPb。所有菘蓝样品中Pb、Hg、As含量均未超出《药用植物及制剂进口绿色行业标准》(WM2—2001),大青叶9.09%样品中Cd超标,且Cd平均污染指数0.7,属警戒限污染等级。因此,在中药材GAP(良好的农业规范)产地环境质量评价时,除板蓝根产地土壤完全符合土壤环境质量二级标准外,也不应忽视板蓝根和大青叶吸收和累积重金属的自身特性。     

APPLICATION OF INCREASING LEVELS OF ZINC TO SOIL REDUCED ACCUMULATION OF CADMIUM IN LUPIN GRAIN

Yellow lupin (Lupinus luteus L.) and narrow-leafed lupin (L. angustifolius L.) are grown as grain legumes in rotation with spring wheat (Triticum aestivum L.) on acidic sandy soils of south-western Australia. Yellow lupin can accumulate significantly larger cadmium (Cd) concentrations in grain than narrow-leafed lupin. A glasshouse experiment was undertaken to test whether adding increasing zinc (Zn) levels to soil increased Zn uptake by yellow lupin reducing accumulation of Cd in yellow lupin grain. Two cultivars of yellow lupin (cv. ‘Motiv’ and ‘Teo’) and 1 cultivar of narrow-leafed lupin (cv. ‘Gungurru’) were used. The soil was Zn deficient for grain production of both yellow and narrow-leafed lupin, but had low levels of native soil Cd (total Cd <0.05 mg kg^?1) so 1.6 mg Cd pot^?1, as a solution of cadmium chloride (CdCl₂·H₂O), was added and mixed through the soil. Eight Zn levels (0–3.2 mg Zn pot^?1), as solutions of zinc sulfate (ZnSO₄·7H₂O), were added and evenly mixed through the soil. Yellow lupin accumulated 0.16 mg Cd kg^?1 in grain when no Zn was applied, which decreased as increasing Zn levels were applied to soil, with ～0.06 mg Cd kg^?1 in grain when the largest level of Zn (3.2 mg Zn pot^?1) was applied. Low Cd concentrations (<0.016 mg Cd kg^?1) were measured in narrow-leafed lupin grain regardless of the Zn treatment. When no Zn was applied, yellow lupin produced ～2.3 times more grain than narrow-leafed lupin, indicating yellow lupin was better at acquiring and using indigenous Zn from soil for grain production. Yellow lupin required about half as much applied Zn as narrow-leafed lupin to produce 90% of the maximum grain yield, ～0.8 mg pot^?1 Zn compared with ～1.5 mg Zn pot^?1. Zn concentration in whole shoots of young plants (eight leaf growth stage) related to 90% of the maximum grain yield (critical prognostic concentration) was (mg Zn kg^?1) 25 for both yellow lupin cultivars and 19 for the narrow-leafed lupin cultivar. Critical Zn concentration in grain related to 90% of maximum grain yield was (mg Zn kg^?1) 24 for both yellow lupin cultivars compared with 20 for the narrow-leafed lupin cultivar.     

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.     

Intercropping of Sonchus asper and Vicia faba affects plant cadmium accumulation and root responses

The cadmium (Cd) pollution of farmland soil is serious in the world. The present study investigated the effects of intercropping Vicia faba and the hyperaccumulator Sonchus asper on the Cd accumulation and root responses (morphology and secreted organic acids) of plants grown on soil from a mining area in Yunnan Province, China, under different Cd stress levels (0, 50, 100, and 200 mg kg^-1). Intercropping increased the biomass of both S. asper and V. faba, as well as the Cd accumulation and Cd transfer coefficient from roots to shoots of S. asper, but decreased those of V. faba in the 200 mg kg^-1 Cd treatment. The Cd concentrations in roots, shoots, and grains from intercropped V. faba plants were positively correlated (P<0.05) with the N,N-diethyl phenylacetamide-extractable Cd content in soil. In the 50 mg kg^-1 Cd treatment, intercropping decreased citric and malic acids in root secretions of S. asper. Intercropped V. faba secreted more citric, oxalic, acetic, and malic acid compared with S. asper. Intercropping also increased root length and root surface area of both S. asper and V. faba. At 50 mg kg^-1 Cd, root length for S. asper was higher than that at 0 mg kg^-1 Cd, whereas V. faba roots had significantly decreased length and mean diameter. Intercropping of S. asper and V. faba is suggested as an in situ phytoremediation strategy of Cd-contaminated soils and may improve the food quality of V. faba.     

Copper Tolerance and Accumulation of Elsholtzia splendens Nakai in a Pot Environment

ABSTRACT

Elsholtzia splendens Naki has been identified as a copper (Cu) geobotanical indicator. In this study, the effects of Cu supply levels (control, 100, 200, 400, 600, 800, 1000, 1200 mg kg¹) on the growth and Cu accumulation in E. splendens were studied in one pot experiment. The results showed that no reduction in shoot height and dry weight was noted when the plants were grown at Cu supply levels up to 1000 mg kg^?1 in soil. Slight stimulation on shoot growth was noted at Cu levels ≥ 100 mg kg^?1. Copper concentration in shoots and roots increased with increasing Cu levels, and reached a maximum of 1751 and 9.45 mg kg^?1 (DW) at 1200 mg Cu kg^?1. The amount of Cu accumulated in the roots and shoots were 313 and 22 μ g plant^?1 at external Cu levels of 1000 and 800 mg kg^?1, respectively. The shoot/root Cu ratios ranged from 0.005 to 0.008 and more than 92% of the total Cu taken up by E. splendens was accumulated in roots. Furthermore, Cu concentrations in roots and shoots were significant and positively correlated with total soil Cu, water, ammonium nitrate (NH₄NO₃), ammonium (NH₄)-acetate, and ethylenediaminetetraacetic acid (EDTA) extractable Cu. These results indicate that E. splendens can considered as a Cu tolerant and accumulated plant, and root is the major part for accumulation of Cu in E. splendens.     

Absorption and accumulation of cadmium by ramie (Boehmeria nivea) cultivars: A field study

Abstract

Ramie is a fibre crop originating from China that has great ability to tolerate and accumulate heavy metals. This study has analysed the capacity of ramie cultivars to absorb and accumulate cadmium (Cd) through two years of micro-regional field study and shown that stress under high concentration of Cd significantly affects the biomass of ramie; 25 mg kg^?1 Cd treatment promotes the growth and development of ramie cultivars B. nivea 1 and 9. The Cd contents retained in different parts of ramie are ranked as the following: bast > stems > leaves. Cd concentrations in shoot systems among different ramie cultivars are significantly different and increase dramatically in association with the increasing Cd concentration in the soil. Ramie has the ability to accumulate large amounts of Cd; under the treatment with 25 and 100 mg kg^?1 of Cd, three times of ramie harvest annually remove 0.76 and 0.97 kg hm^?2 a^?1 of Cd respectively. The results from this study demonstrate the feasibility of phytoremediation of Cd-contaminated farmland by ramie cultivars that have obtained Cd accumulating capacity through screening and training.     

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。     

Arsenic and heavy metal accumulation by Athyrium yokoscense from contaminated soils

Abstract

Athyrium yokoscense, a type of fern that grows vigorously in mining areas in Japan, is well known as a Cd hyperaccumulator as well as a Cu, Pb and Zn tolerant plant. However, no information is available on As accumulation of A. yokoscense, although it often grows on soils containing high levels of both heavy metals and As. In this study, young ferns collected from a mine area were grown in media containing As-spiked soils or mine soil in a greenhouse for 21 weeks. Athyrium yokosense was highly tolerant to arsenate and survived in soils containing up to 500 mg As (V) kg^?1. The addition of 100 mg As (V) kg^?1 resulted in the highest fern biomass (1.95 g plant^?1) among As-spiked soils. Although the As concentration of the fern was lower than other As hyperaccumulators, such as Pteris vittata, A. yokoscense could hyperaccumulate As in mature and old fronds. Arsenic was accumulated most efficiently in old fronds (922 mg kg^?1) in the media containing 5 mg As (III) kg^?1. Moreover, higher As accumulation was found in the roots of the ferns, with a range from 506 to 2,192 mg kg^?1. In addition, in the mine soil with elevated concentrations of As and heavy metals, A. yokoscense not only hyperaccumulated As (242 mg As kg^?1 in old fronds), but also accumulated Cd, Pb, Cu and Zn at concentrations much higher than those reported for other terrestrial plants. Athyrium yokoscense accumulated Cd mostly in fronds in high concentrations, up to 1095 mg kg^?1, while it accumulated Cu, Zn and Pb mainly in the roots and the concentrations were 375, 2040 and 1165 mg kg^?1, respectively.     

Effects of soil properties and cultivar on cadmium accumulation in wheat grain

Cd accumulation in the grain of wheat cultivars grown on soils at seven experimental sites in the Austrian wheat zone was significantly affected by soil chemical characteristics and by cultivar. Multiple linear regression analyses indicate that about 80% of the variation in Cd accumulation may be explained by cultivar. total soil Cd, and organic carbon (OC). An additional 10% of the variation was correlated with Cl^? and Ca²⁺ in the soil solution. Uptake of Cd increased with higher soil Cd content and higher Cl^? concentrations in soil solution, but decreased at higher levels of OC and soluble Ca. Cd accumulation varied by a factor of up to 2.5 among cultivars. The highest Cd accumulation was found in some spring durum cultivars in soils containing relatively low total Cd (< 0.4 mg kg^?1); at some sites the maximum permissible Cd concentrations in wheat grain (0.1 mg kg^?1) was exceeded according to German regulations. Selecting low Cd-accumulating cultivars and adjusting soil chemical conditions may provide alternatives to reduce Cd intake in human diet.     

Cadmium and zinc accumulation in willow and poplar species grown on polluted soils

Woody plant species that produce high biomass have been proposed for use in phytoremediation technology. We investigated the accumulation of cadmium (Cd) and zinc (Zn) in Salix babylonica, S. caprea, S. dasyclados, S. matsudana × alba, S. purpurea, S. smithiana, Populus tremula, and P. nigra clones grown in a pot experiment on a Calcaric and a Eutric Cambisol (pH 7.2 and 6.4) of different levels of contamination (total metal concentrations in mg kg^–1 in soil A: 32.7 Cd, 1760 Zn; soil B: 4.34 Cd, 220 Zn). Generally, the tested clones tolerated large metal concentrations in soils and had larger Cd and Zn concentrations in leaves compared to the roots. The largest Cd concentrations in leaves were found in two clones of S. smithiana (440 mg kg^–1 on soil A; 70 mg kg^–1 on soil B). One of the S. smithiana clones had also the largest Zn concentrations (870 mg kg^–1) on soil B but accumulated slightly less Zn than a S. matsudana × alba clone (2430 mg kg^–1) on soil A. The Cd concentrations in leaves of both S. smithiana clones on soil A are the largest ever reported for soil‐grown willows. The bioconcentration factors of the best performing clone reached 15.9 for Cd and 3.93 for Zn on the less contaminated soil B. Also based on the metal contents in leaves, this clone was identified as the most promising for phytoextraction. The metal concentrations in leaves observed in the pot experiment do not reflect those found in a previous hydroponic study and the leaf‐to‐root ratios are clearly underestimated in hydroponic conditions. This demonstrates the need for testing candidates for phytoextraction crops on soils rather than in hydroponics. Our data also show that the phytoextraction potential should be tested on different soils to avoid misleading conclusions.     

MICRONUTRIENT COMPOSITION OF PAPAVER SOMNIFERUM L. GROWN UNDER LOW CADMIUM STRESS CONDITION

Micronutrient uptake and distribution within poppy plants (Papaver somniferum L.) were studied in two pot experiments using a loamy garden soil as substrate. In the first experiment a supplement of increasing cadmium (Cd) concentrations to the substrate and in the second the influence of cultivars and harvest time were studied. At the stage of seed ripening the taproots were already decaying, and the Cd concentration in the shoot reflected the Cd supply in the substrate. In the shoot the highest Cd concentrations were found in seeds. With 24 mg Cd per pot (6 mg kg^?1), Cd concentration reached 1.7 mg kg^?1.

The four poppy varieties (Edel-Weiss, Marianne, Soma, White Poppy) differed clearly in seed production but reached comparable Cd concentrations of about 1.3 mg kg^?1 in the seeds at the second harvest. Seeds made up 2.5 to 12.9% of shoot biomass, but stored 15 to 42% of total Cd in the shoot, which indicates a preferential translocation of Cd into seeds in this plant species.

In addition, Cd supply had a marginal effect on the concentration of micronutrients in seeds and stems + leaves. At the highest Cd supply of 6 mg Cd kg^?1 soil a growth reduction of about 25% could be observed.     

Liming and Cultivars Affect Root Growth,Nodulation, Leaf to Stem Ratio,Herbage Yield,and Elemental Composition of Alfalfa on an Acid Soil

Abstract

Soil acidity is one of the limiting factors affecting the production and sustainability of pastures and crops in many parts of the world. An on‐farm experiment was conducted in Australia to investigate the cultivar variation in alfalfa (lucerne) (Medicago sativa L.) with respect to soil acidity and response to applied lime. The experimental site was a brown sandy clay loam with a soil pH of 4.8 (1:5 calcium chloride). Ten cultivars (Hunter River, Hunterfield, Sceptre, Aurora, Genesis, Aquarius, Venus, PL90, PL55, and breeding line Y8804) were tested at two levels of lime (0 and 2 t ha^?1). Lime application significantly increased the root growth, nodulation, leaf retention, leaf to stem ratio, herbage yield, and crude protein content of alfalfa. Liming had a significant effect on elemental composition of alfalfa shoots. Aluminum (Al) concentration was reduced from 93 mg kg^?1 DM in nil lime treatment to 45 mg kg^?1 DM in +lime treatment. Similarly, manganese (Mn) and iron (Fe) shoot concentrations were reduced from 74 mg kg^?1 DM and 92 mg kg^?1 DM to 59 mg kg^?1 DM and 76 mg kg^?1 DM, respectively. Liming significantly improved the calcium (Ca) concentration of shoots, while there was a little effect on phosphorus (P) and zinc (Zn) concentrations of alfalfa shoots. Cultivars had differential response to lime application. Response to lime application was greater in Y8804 and Aurora alfalfa where yield increased by 32% and 31%, while yield increase was 11–22% in other cultivars. Cultivars also differed significantly in root growth, nodulation, leaf drop, leaf to stem ratio, crude protein content, and elemental composition of shoots. Cultivars with better performance in no liming treatment had comparatively lower shoot Al, Mn, and Fe concentrations compared with other cultivars.     

Phosphorus Efficiency in Sunflower Cultivars and Its Relationships with Phosphorus,Calcium, Iron,Zinc and Manganese Nutrition

ABSTRACT

Phosphorus (P) efficiency (shoot dry weight at low P/shoot dry weight at high P) of a cultivar is the ability to produce a high yield in a soil that is limited in that element for a standard genotype. The large variation in P efficiency of different crops provides opportunities for screening crop species that perform well on low phosphorus soil. To explain the differences in P efficiency of sunflower (Helianthus annuus L.) cultivars a glasshouse pot experiment was conducted by using P-deficient soil [0.5 M sodium bicarbonate (NaHCO₃)-extractable P 8.54 mg kg^?1] treated with 0 (low P) and 100 mg P kg^?1 soil (high P). The relationship between P efficiency and P, calcium (Ca), iron (Fe), zinc (Zn), and manganese (Mn) nutrition and anthocyanin accumulation was investigated in ten sunflower cultivars. Phosphorus deficiency resulted in significant decreases in the shoot and root yield. Phosphorus-efficient cultivars have the ability to produce higher yield than the inefficient cultivars in a limited P conditions. Our results showed that P-efficient cultivars had lower P concentrations, but higher P content in low P conditions. Phosphorus-efficient cultivars also have lower Ca and Fe concentrations in low P conditions but not in P-sufficient conditions. Applied P resulted in significant decreases in Zn concentrations in the shoots of the cultivars. Anthocyanin concentrations showed an accumulating pattern in all cultivars under P deficiency. The results demonstrated that phosphorus efficiency of the sunflower cultivars depends on their ability to produce higher yield and take up more P, and lower the concentration of Ca and Fe in shoots under low P conditions.     

Arsenic and Cadmium Phytoextraction Potential of Crambe Compared with Indian Mustard

ABSTRACT

The ability to tolerate and accumulate arsenic (As) and cadmium (Cd) was compared between Brassica juncea (Indian mustard) and Crambe abyssinica (Hochst.) (Crambe or Abyssinian mustard). Plants were grown hydroponically and treated with 70 μM sodium arsenate or 50 μ M cadmium chloride for two weeks. When nutrients were omitted during the As treatment, leaves of C. abyssinica accumulated an average of 140 mg As kg^?1, compared with 34 mg kg^?1 for B. juncea. When quarter-strength Hoagland's nutrient solution was provided during As treatment, leaves of C. abyssinica accumulated an average of 270 mg As kg^?1, compared with 13 mg kg^?1 for B. juncea. Cadmium accumulation on a dry-weight basis was approximately two times greater in shoots of B. juncea. Shoot biomass production in the presence or absence of metals was greatest for C. abyssinica. Because of its larger biomass and more efficient accumulation of As, C. abyssinica should be considered for use in phytoremediation research.     

不同Zn浓度对黑麦草根分泌物、根际Zn形态及植物Zn蓄集的影响

A glasshouse experiment was conducted using a root-bag technique to study the root exudates, rhizosphere Zn fractions, and Zn concentrations and accumulations of two ryegrass cultivars (Lolium perenne L. cvs. Airs and Tede) at different soil Zn levels (0, 2, 4, 8, and 16 mmol kg-1 soil). Results indicated that plant growth of the two cultivars was not adversely affected at soil Zn level≤8 mmol kg-1. Plants accumulated more Zn as soil Zn levels increased, and Zn concentrations of shoots were about 540 /μg g-1 in Aris and 583.9μg g-1 in Tede in response to 16 mmol Zn kg-1 soil. Zn ratios of shoots to roots across the soil Zn levels were higher in Tede than in Airs, corresponding with higher rhizosphere available Zn fractions (exchangeable, bound to manganese oxides, and bound to organic matter) in Airs than in Tede. Low-molecular-weight (LMW) organic acids (oxalic, tartaric, malic, and succinic acids) and amino acids (proline, threonine, glutamic acid, and aspartic acid, etc.) were detected in root exudates, and the concentrations of LMW organic acids and amino acids increased with addition of 4 mmol Zn kg-1 soil compared with zero Zn addition. Higher rhizosphere concentrations of oxalic acid, glutamic acid, alanine, phenylalanine, leucine, and proline in Tede than in Airs likely resulted in increased Zn uptake from the soil by Tede than by Airs. The results suggested that genotypic differences in Zn accumulations were mainly because of different root exudates and rhizosphere Zn fractions.     

Effects of Graded Levels of Cadmium on Spinach and Cabbage Grown in an Inceptisol

Cadmium (Cd) contamination of the soil and its concentrations in spinach and cabbage were studied in a pot culture experiment. Eight levels of Cd (0–100 mg kg^?1 soil) were applied singly. Application of Cd of up to 10 and 15 mg kg^?1 resulted in safe Cd concentrations (1.56 and 1.38 mg kg^?1) in the shoots of spinach and cabbage, respectively, at the consumable stage. The total chlorophyll content gradually decreased with the addition of Cd, and the maximum decreases were 31.7 and 32% in spinach and cabbage, respectively, at 60 days of crop growth in the treatment Cd₁₀₀ over the control. The greatest diethylene triamine penta-acetic acid (DTPA)–extractable Cd contents in the postharvest soil of spinach and cabbage were 22.09 and 24.22 mg kg^?1, respectively, in the treatment Cd₁₀₀. The DTPA Cd was significantly negatively correlated with leaf area and total chlorophyll content while positively correlated with root and shoot Cd concentrations of spinach and cabbage.