Effect of Cadmium and Iron on Rice (Oryza Sativa L.) Plant in Chelator-Buffered Nutrient Solution

ABSTRACT

To better understand the mechanisms responsible for differences in uptake and distribution of cadmium (Cd), nutrient-solution experiments were conducted with different varieties of rice (Oryza sativa), ‘Khitish’ and ‘CNRH3’. The plants were grown in a complete nutrient solution with different levels of pCd (-log free Cd⁺² activity) and pFe [-log free iron (Fe⁺²) activity]. The required concentrations of chelating agent and metals were determined using a computerized chemical equilibrium model such as Geochem-PC. Experimental treatments included a combination of four pCd activity levels (0, 7.9, 8.2, and 8.5) applied as Cd (NO₃)₂ 4H₂O, and two pFe activity levels (17.0 and 17.8) applied as FeCl₃. The application of both Cd and Fe in solution culture significantly affected plant growth, yield, and Cd accumulation in plant tissue. In general, yield of rice was decreased by an increase in amount of solution Cd; however, yield response varied among the cultivars. At the 7.9 pCd level, yields of rice cultivars ‘Khitish’ and ‘CNRH3’ were reduced to 69% and 65%, respectively, compared with control plants. Root Cd concentrations ranged from 2.6 mg kg^?1 (control plants) to 505.7 mg kg^?1 and were directly related to solution Cd concentrations. In rice plants, Cd toxicity symptoms resembled Fe chlorosis. Differential tolerance of varieties to phytotoxicity was not readily visible, but a significant interaction of substrate Cd and variety was obtained from dry-matter yields. Significant interactions indicated that response of tissue Cd concentration, plant Cd uptake, and translocation of Cd to the aerial parts were dependent on variety as well as substrate Cd. Uptake of Cd by roots was significantly higher than by shoots. Higher Cd uptake by rice plants decreased the uptake of other beneficial metals.

The effect of Cd and Fe on the rate of phytometallophore release was also studied in the nutrient solution. Among the rice genotypes, ‘Khitish’ was the most sensitive to Cd toxicity. In both genotypes, with the onset of visual Cd-toxicity symptoms, the release of phytometallophore (PM) was enhanced. Among the rice varieties, ‘Khitish’ had the highest rate of PM release. Treatments with the metal ions studied produced a decrease in chlorophyll and enzyme activity. A decrease in concentrations of chlorophyll pigments in the third leaf was observed due to the highest activity level of Cd (pCd 7.9). Activities of enzymes such as peroxidase (POD) and superoxide dismutase (SOD) are altered by toxic amounts of Cd. Changes in enzyme activities occurred at the lowest activity of Cd (pCd 8.5) in solution. Peroxidase activity increased in the third leaf. Results showed that in contrast with growth parameters, the measurements of enzyme activities may be included as early biomarkers in a plant bioassay to assess the phytotoxicity of Cd-contaminated solution on rice plants. Evidence that Cd uptake and translocation are genetically controlled warrants the selection of varieties that assimilate the least Cd and that translocate the least metal to the plant part to be used for human and animal consumption.     

Amendment-Induced Immobilization of Lead in a Lead-Spiked Soil: Evidence from Phytotoxicity Studies

Lead immobilization was evaluated on soils spiked with increasingconcentrations of Pb (as Pb-acetate) using the following soilamendments: bentonite, zeolite, cyclonic ash, compost, lime,steelshot, and hydroxyapatite. The immobilization efficacy of theamendments was evaluated according to the following criteria:Ca(NO₃)₂-extractable Pb as an indicator of Pbphytoavailability, morphological and enzymatic parameters of beanplants (Phaseolus vulgaris) as indicator of phytotoxicity, and Pb concentration in edible tissue of lettuce (Lactuca sativa). The lowest reductions in Ca(NO₃)₂-extractablesoil Pb occurred when bentonite and steelshot were applied. Phytotoxicity from application of steelshot was confounded by toxic amounts of Fe and Mn released from the by-product which killed the lettuce seedlings. Addition of zeolite induced poorplant growth independent of Pb concentration due to its adverseeffect on soil structure. Substantial reductions in Ca(NO₃)₂-extractable Pb were observed when cyclonic ash, lime, compost and hydroxyapatite were applied. In general,these amendments reduced Pb phytotoxicity concomitant with reduced Pb concentration in lettuce tissue. Cyclonic ash, limeand compost further improved plant growth and reduced oxidativestress at low soil Pb concentrations due to soil pH increase mitigating Al or Mn toxicity.     

Heavy Metal Content in Lettuce Plants Grown in Biosolids Compost

The objective of this work was to evaluate the affects of the application of composted biosolids on the accumulation of heavy metals (Cd, Cu, Ni, Pb and Zn) in lettuce leaves. Pots containing different proportions (0 to 100%) of composted biosolids were used to grow lettuce plants under greenhouse conditions. Dry and fresh weight, leaf area and Cd, Cu, Ni, Pb and Zn uptake were determined after harvest. It was found that the dry and fresh matter productions of the plants were significantly lower in the control treatment. The addition of composted biosolids caused a 20 and 40% increase in biomass accumulation. Cd and Pb concentrations in leaves were below detection limits (0.05 mg kg^?1) in all treatments. Zn concentration in leaves increases as compost proportion decreases, ranging from 57.2 to 80.4 mg kg^?1. Composted biosolids application increased the Cu and Ni plant concentrations, ranging from 5.1 to 9.8 mg Cu kg^?1 and 2.3 to 3.7 mg Ni kg^?1. In all treatments the proportions of heavy metals in plants were below the international standards of toxicity. The results allow us to suggest that, in short-term applications, composted biosolids could be used as soil amendment for lettuce production, without toxic effects in the chemical composition of the plant.     

Effect of type of compost and application rate on growth and quality of lettuce plant

Abstract

This study intends to assess the effect of compost types and rates on lettuce growth. A pot experiment was conducted at the greenhouse of the College of Agriculture and Veterinary Medicine experimental station, Saudi Arabia. Three types (chicken residues, animal residues, and mixed organic residues) and four rates (1%, 2%, 4%, and 6%) were added to sandy soil. Lettuce seeds were sown in a nursery. After two weeks, each seedling was transplanted to a pot that contained 15?kg of soil. The lettuce plants were irrigated regularly for 60?days, then harvested following dry weight (DW) and chemical analyses. The results showed great variation in the DW, nutrient content, and heavy metals concentrations between the different compost treatments. It noted that DW of lettuce decreased with increasing rates of compost in certain treatments. Moreover, no plant growth occurred in some treatments derived from the mixed organic residue with higher application rates. The nutrient status of lettuce tissues varies greatly among different types of compost. The concentration of heavy metals and microelements present within the lettuce tissues was significantly affected by the types of compost. Copper (Cu), Zinc (Zn), Lead (Pb), Cadmium (Cd), and Nickel (Ni) concentrations in lettuce tissues ranged between 7.4 and 9.6, 81.5 and 104, 23.3 and 28.2, 3.7 and 5.8, and 27 and 30?mg kg^?1, respectively. It revealed that heavy metals concentration increased in lettuce tissues with an increasing application rate of composts. The content of Zn, Pb, Cd, and Ni in lettuce plants were higher and did not meet the requirement set by national standards.     

The effect of EDDS chelate and inoculation with the arbuscular mycorrhizal fungus Glomus intraradices on the efficacy of lead phytoextraction by two tobacco clones

Two pot experiments were conducted to investigate the effect of inoculation with the arbuscular mycorrhizal (AM) fungus Glomus intraradices on Pb uptake by two clones of Nicotiana tabacum plants. Non-transgenic tobacco plants, variety Wisconsin 38, were compared in terms of Pb uptake with transgenic plants of the same variety with inserted gene coding for polyhistidine anchor in fusion with yeast metallothionein. Bioavailability of Pb in experimentally contaminated soil was enhanced by the application of a biodegradable chelate ethylenediaminedissuccinate (EDDS).EDDS addition (2.5 and 5.0 mmol kg⁻¹ substrate) increased Pb uptake from the substrate and enhanced Pb translocation from the roots to the shoots, with shoot Pb concentrations reaching up to 800 mg kg⁻¹ at the higher chelate dose. Application of a single dose of 5 mmol kg⁻¹ proved to be more efficient at increasing shoot Pb concentrations than two successive doses of 2.5 mmol kg⁻¹, in spite of a marked negative effect on plant growth and phytotoxicity symptoms. Pb amendment (1.4 g kg⁻¹ substrate) connected with either dose of EDDS decreased significantly plant biomass as well as reduced the development of AM fungi. AM inoculation promoted the growth of tobacco plants and partly alleviated the negative effect of Pb contamination, mainly in the case of root biomass.No consistent difference in Pb uptake was found between transgenic and non-transgenic tobacco plants. The effect of AM inoculation on Pb concentrations in plant biomass varied between experiments, with no effect observed in the first experiment and significantly higher root Pb concentrations and increased root–shoot ratio of Pb concentrations in the biomass of inoculated plants in the second experiment. Due to probable retention of Pb in fungal mycelium, the potential of AM for phytoremediation resides rather in Pb stabilisation than in phytoextraction.     

Relationship between lead uptake by lettuce and water-soluble low-molecular-weight organic acids in rhizosphere as influenced by transpiration

The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce plants under high and low transpiration. A physiological mechanism of the roots of lettuce plants governing the relationship between Pb contamination level and quantity of water-soluble LMWOAs in rhizosphere quartz sand and resin, as influenced by transpiration, was proposed.     

Effect of Application of Chromium Feedstock Compost on the Growth and Bioavailability of Some Trace Elements in Lettuce

A pot experiment was conducted to investigate the effect of chromium compost (0, 10, 30, and 50%) on the growth and the concentrations of some trace elements in lettuce (Lactuca sativa L.) and in the amended soils. Compost addition to the soil (up to 30%) increased dry matter yield (DMY); more than 30% decreased DMY slightly. The application of compost increased soil pH; nitric acid (HNO₃)–extractable copper (Cu), chromium (Cr), lead (Pb), and zinc (Zn); and diethylenetriaminepentaacetic acid (DTPA)–, Mehlich 3 (M3)–, and ammonium acetate (AAc)–extractable soil Cr and Zn. The addition of Cr compost to the soil increased tissue Cr and Zn but did not alter tissue cadmium (Cd), Cu, iron (Fe), manganese (Mn), nickel (Ni), and Pb. The Cr content in the lettuce tissue reached 5.6 mg kg^?1 in the 50% compost (326 mg kg^?1) treatment, which is less than the toxic level in plants. Our results imply that compost with high Cr could be used safely as a soil conditioner to agricultural crops.     

深色有隔内生真菌柱孢顶囊壳对玉米幼苗生长、光合作用及耐铅能力的影响

Dark septate endophytic (DSE) fungi are ubiquitous and cosmopolitan,and occur widely in association with plants in heavy metal stress environment.However,little is known about the effect of inoculation with DSE fungi on the host plant under heavy metal stress.In this study,Gaeumannomyces cylindrosporus,which was isolated from Pb-Zn mine tailings in China and had been proven to have high Pb tolerance,was inoculated onto the roots of maize (Zea mays L.) seedlings to study the effect of DSE on plant growth,photosynthesis,and the translocation and accumulation of Pb in plant under stress of different Pb concentrations.The growth indicators (height,basal diameter,root length,and biomass) of maize were detected.Chlorophyll content,photosynthetic characteristics (net photosynthetic rate,transpiration rate,stomatal conductance,and intercellular CO2 concentration),and chlorophyll fluorescence parameters in leaves of the inoculated and non-inoculated maize were also determined.Inoculation with G.cylindrosporus significantly increased height,basal diameter,root length,and biomass of maize seedlings under Pb stress.Colonization of G.cylindrosporus improved the efficiency of photosynthesis and altered the translocation and accumulation of Pb in the plants.Although inoculation with G.cylindrosporus increased Pb accumulation in host plants in comparison to non-inoculated plants,the translocation factor of Pb in plant body was significantly decreased.The results indicated that Pb was accumulated mainly in the root system of maize and the phytotoxicity of Pb to the aerial part of the plant was alleviated.The improvement of efficiency of photosynthesis and the decrease of translocation factor of Pb,caused by DSE fungal colonization,were efficient strategies to improve Pb tolerance of host plants.     

不同马铃薯品种对Cd、Pb吸收累积的差异

采用田间试验法,以中南地区主要种植的11个马铃薯品种为研究对象,测定马铃薯植株各部位重金属Cd、Pb含量,探讨不同品种的马铃薯对Cd、Pb的吸收累积差异,为马铃薯的安全种植提供实践参考。结果表明:Cd—Pb复合污染下,马铃薯块茎鲜重、茎叶鲜重以及根、茎叶、块茎中Cd、Pb含量在品种间均表现出显著差异。11个马铃薯品种块茎Cd含量范围为0.39～0.67 mg/kg,超标率100%,块茎Pb含量为0.16～0.43 mg/kg,超标率81.8%。马铃薯各部位Cd、Pb含量均呈现根茎叶块茎的分布特点;马铃薯对Cd的富集系数为2.35～5.56,对Pb富集系数为0.11～0.22,马铃薯富集转运Cd的能力大于Pb。尽管复合重金属靶标危险系数(TTHQ)法评价显示,金湘等5种马铃薯的TTHQ值1,对人体健康风险较小,但结合块茎Cd、Pb含量,建议污染区种植的马铃薯作为工业原料使用更安全。     

有机物料及其用量对生菜生长与Pb含量的影响

为了降低叶菜中重金属Pb的含量,选择有机肥、猪粪、牛粪、鸡粪和花生麸5种有机物料为材料,分别以0.5%、1%、2%、4%4个水平的用量施入重金属污染土壤,通过种植3茬生菜（Lactuca sativa L.）的盆栽试验研究有机物料对重金属污染土壤上生菜生长及其Pb含量的影响。结果表明,与对照相比,有机物料利于生菜生长,有提高生菜生物量的趋势;大部分有机物料处理没有显著影响生菜地上部分的Pb含量;5种有机物料中,仅牛粪有提高生菜地上部Pb含量的趋势;生菜Pb含量平均值高低的顺序为牛粪〉鸡粪〉花生麸〉有机肥〉猪粪,但不同有机物料之间没有显著差异。与对照相比,大部分处理没有显著影响土壤的DTPA-Pb含量,初步揭示了供试有机物料没有显著影响生菜地上部Pb含量的原因。     

有机无机配施对生菜生长及其CdPb含量的影响

为了比较等氮水平下不同有机肥及其与无机肥配施对土壤重金属的钝化效果,通过在0.2 g·kg-1氮水平下单施商品有机肥、猪粪、牛粪、鸡粪和花生麸,及5种有机肥分别与无机肥（尿素＋磷酸二氢钙＋硫酸钾）配施（N∶N=1∶1）的盆栽试验,研究它们对重金属污染土壤上生菜（Lactuca sativa）生长及其Cd、Pb含量的影响。结果表明,与CK相比,有机肥可提高生菜的生物量（商品有机肥单施除外）,有机肥单施时,鸡粪处理生菜的鲜重最高,配施时牛粪和鸡粪处理生菜的生物量最大。无论单施或配施,花生麸和鸡粪处理降低生菜地上部Cd含量的效果最好,且鸡粪较好地降低了生菜地上部Pb含量。牛粪和花生麸配施的Pb含量显著低于单施,猪粪和商品有机肥单施的Pb含量显著低于配施,其余单施和配施之间没有显著差异。因此,鸡粪是5种有机肥中较适合施用于重金属污染菜地土壤的有机肥。     

The influence of the form of nitrogen nutrition on uptake and distribution of cadmium in lettuce varieties

Four lettuce (Lactuca saliva L.) varieties ('Benita’, ‘Wendy’, ‘Mirena’, and ‘Jacky') were grown for 43 days in a pH‐controlled complete nutrient solution without cadmium (Cd) or with either 0.01 or 0.03 mg Cd/1 and with NH₄ or NO₃ as the form of nitrogen nutrition. Cadmium did not affect dry matter yield. ‘Wendy’ had a significantly higher total dry matter production when grown on NO₃ compared to NH₄, whereas growth of ‘Mirena’ was best on NH₄ (P<0.05). Dry weights of ‘Benita’ and ‘Jacky’ were not affected by the N source. Cadmium concentrations in shoots (and roots) of plants grown on NH₄ were significantly higher than in plants grown on NO₃. The Zn concentrations in the shoots were also enhanced. The distribution of Cd in the lettuce varieties was independent of the form of N nutrition. It is concluded that the N source directly affects the amount of Cd taken up, without influencing the Cd distribution.     

EDTA-Enhanced Phytoremediation of Lead-Contaminated Soil by Corn

EDTA-enhanced phytoremediation by corn (Zea mays L.) of soil supplemented with 500 mg L^?1 lead (Pb) was examined. The chelate EDTA was used in order to increase Pb bioavailability at four levels: 0 (control), 0.5 (low), 1.0 (medium), and 2.5 mmol kg^?1 (high). Plants were grown under controlled conditions in a growth-chamber with supplementary light. An EDTA concentration of 5.0 mmol kg^?1 was lethal to plants. At high and medium EDTA levels plants grew significantly less than control ones. Lead concentrations in corn leaves increased with increased EDTA levels. Plants subjected to medium EDTA level had the greatest root to shoot Pb translocation. Plants subjected to high EDTA level showed high phosphorus (P) uptake and translocation within plants. Therefore, possibly it was not only Pb that caused toxic effect on plants, but also the high internal concentration of P that in turn could have complexed active Fe.     

Impact of an Urban Environment on Trace Element Concentrations in Domestically Produced Lettuce (<Emphasis Type="Italic">Lactuca sativa L.</Emphasis>)

Urban horticulture is gaining more and more attention in the context of sustainable food supply. Yet, cities are exposed to (former) industrial activities and traffic, responsible for emission of contaminants. Trace elements were monitored in soils located in the urban environment of Ghent (Belgium) and 84 samples of Lactuca satica L. lettuce grown on it. The effects of cultivation in soil versus trays, neighbouring traffic and washing of the lettuce before consumption were studied. The 0–30 cm top layer of soils appeared heterogenic in composition and enriched in Co, Cd, Ni and Pb within 10 m from the nearest road. Yet, no similar elevated concentrations could be found in the crops, except for As. Besides uptake from the roots, the presence of trace elements in the plants is also caused by the atmospheric deposition of airborne particulate matter on the leaf surface. Correlation analysis and principal component analysis (PCA) revealed that this latter transport pathway might particularly be the case for Pt, Pd and Rh. Concentrations of Cd did not exceed the 0.2 mg kg^?1 (fresh weight) threshold for Cd in leafy vegetables set by the European Commission. Measurements to reduce the health risks include the washing of lettuce, which effectively reduced the number of samples trespassing the maximum Pb level of 0.3 mg kg^?1 (fresh weight). Also, cultivation in trays resulted in a lower As content in the plants. Taking into account a vigilance on crop selection, cultivation substrate and proper washing before consumption are considered essential steps for safe domestic horticulture in urban environments.     

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.     

The Zinc Adsorption Study by Using Orhaneli Fly Ash, Bentonite, and Molasses in Wastewater

To assess strategies for mitigating Pb and As transfer into leafy vegetables from contaminated garden soils, we conducted greenhouse experiments using two field-contaminated soils amended with materials expected to reduce metal phytoavailability. Lettuce and mustard greens grown on these soils were analyzed by ICP-MS, showing that some Pb and As transfer into the vegetables occurred from both soils tested, but plant Pb concentrations were highly variable among treatment replicates. Soil-to-plant transfer was more efficient for As than for Pb. Contamination of the leaves by soil particles probably accounted for most of the vegetable Pb, since plant Pb concentrations were correlated to plant tissue concentrations of the immobile soil elements Al and Fe. This correlation was not observed for vegetable As concentrations, evidence that most of the soil-to-plant transfer for this toxic metal occurred by root uptake and translocation into the above-ground tissues. A follow-up greenhouse experiment with lettuce on one of the two contaminated soils revealed a lower and less variable foliar Pb concentration than observed in the first experiment, with evidence of less soil particle contamination of the crop. This reduced transfer of Pb to the crop appeared to be a physical effect attributable to the greater biomass causing reduced overall exposure of the above-ground tissues to the soil surface. Attempts to reduce soil Pb and As solubility and plant uptake by amendment at practical rates with stabilizing materials, including composts, peat, Ca phosphate, gypsum, and Fe oxide, were generally unsuccessful. Only Fe oxide reduced soluble As in the soil, but this effect did not persist. Phosphate amendment rapidly increased soil As solubility but had no measurable effect on either soil Pb solubility or concentrations of Pb or As in the leafy vegetables. The ineffectiveness of these amendments in reducing Pb transfer into leafy vegetables is attributed in this study to the low initial Pb solubility of the studied soils and the fact that the primary mechanism of Pb transfer is physical contamination.     

Effect of synthetic nano-hydroxyapatite as an alternative phosphorus source on growth and phosphorus nutrition of lettuce (Lactuca sativa L.) plant

Phosphorus (P) is one of the least available mineral nutrients to the plants in calcareous and alkaline soils. In this study, we investigated the synthesis, characterization and use of synthetic nano-hydroxyapatite (NHA), P uptake by plants as well as its residual effects. Soluble P source (H₃PO₄) was also included as treatment for comparison. NHA prepared by wet chemical techniques, characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and elemental dispersive X-ray (EDX) analysis. NHA and H₃PO₄ were applied at a rate of 200 mg kg^?1 to find out their effects on phosphorus nutrition and growth of lettuce on the low and high calcareous soil. In addition to this, residual effects of NHA and H₃PO₄ were also determined for lettuce plants grown after first lettuce plants in the both soil. Dry weights of the first and second lettuce plants grown in low and high calcareous soil were significantly increased by applied phosphorus regardless of the source. NHA seems to be more effective than that of ordinary phosphorus source (H₃PO₄-P) on growth and P concentration of the lettuce plants. The promising results of this study needs to be supported with long term field studies regarding the uptake, translocation and interactions of nano-P with the other elements.     

Genotype x environment interaction in the uptake of Cs and Sr from soils by plants

The soil‐plant transfer factors for Cs and Sr were analyzed in relationship to soil properties, crops, and varieties of crops. Two crops and two varieties of each crop: lettuce (Lactuca sativa L.), cv. Salad Bowl Green and cv. Lobjoits Green Cos, and radish (Raphanus sativus L.), cv. French Breakfast 3 and cv. Scarlet Globe, were grown on five different soils amended with Cs and Sr to give concentrations of 1 mg kg^–1 and 50 mg kg^–1 of each element. Soil‐plant transfer coefficients ranged between 0.12–19.10 (Cs) and 1.48–146.10 (Sr) for lettuce and 0.09–13.24 (Cs) and 2.99–93.00 (Sr) for radish. Uptake of Cs and Sr by plants depended on both plant and soil properties. There were significant (P ≤ 0.05) differences between soil‐plant transfer factors for each plant type at the two soil concentrations. At each soil concentration about 60 % of the variance in the uptake of the Cs and Sr was due to soil properties. For a given concentration of Cs or Sr in soil, the most important factor effecting soil‐plant transfer of these elements was the soil properties rather than the crops or varieties of crops. Therefore, for the varieties considered here, soil‐plant transfer of Cs and Sr would be best regulated through the management of soil properties. At each concentration of Cs and Sr, the main soil properties effecting the uptake of Cs and Sr by lettuce and radish were the concentrations of K and Ca, pH and CEC. Together with the concentrations of contaminants in soils, they explained about 80 % of total data variance, and were the best predictors for soil‐plant transfer. The different varieties of lettuce and radish gave different responses in soil‐plant transfer of Cs and Sr in different soil conditions, i.e. genotype x environment interaction caused about 30 % of the variability in the uptake of Cs and Sr by plants. This means that a plant variety with a low soil‐plant transfer of Cs and Sr in one soil could have an increased soil‐plant transfer factor in other soils. The broad implications of this work are that in contaminated agricultural lands still used for plant growing, contaminant‐excluding crop varieties may not be a reliable method for decreasing contaminant transfer to foodstuffs. Modification of soil properties would be a more reliable technique. This is particularly relevant to agricultural soils in the former USSR still affected by fallout from the Chernobyl disaster.     

Arsenic and Heavy Metal Uptake and Accumulation in Native Plant Species from Soils Polluted by Mining Activities

Arsenic and heavy metal (specifically Cd, Cr, Cu, Ni, Pb, and Zn) uptake, translocation, and accumulation in ten native plant species spontaneously growing in soils polluted by mining activities were studied, with a focus on future phytoremediation work in polluted soils. Plant and soil samples were collected in the vicinity of the Mónica mine (NW Madrid, Spain). Soil analysis showed the ability of native plants for growing in soils with high concentration levels of Cd, Cu, Pb, Zn, and especially As. From these elements, the highest percentage of extractable elements was found for Cd and the lowest for Pb. A highly significant correlation was observed between total and extractable element concentrations in soils, except for Cu, indicating that total concentration is the most relevant factor for element mobility in these soils. Extractable elements in soils were better correlated with concentrations in plants than total elements in soils; thus, extraction methods applied are suitable to estimate the element phytoavailable fraction in soils, which depends on the plant species and not only on the element mobility in soils. High element concentrations were found in the aboveground parts of Corrigiola telephiifolia (As and Pb), Jasione montana (Cd and Zn), and Digitalis thapsi (As, Cd, Cu, Pb and Zn). However, considering the translocation and accumulation factors, together with the concentration levels found in roots and aboveground parts, only C. telephiifolia could be considered a Pb accumulator and an As hyperaccumulator plant, which could be used for future phytoremediation work in soils polluted with As.     

Ligands involved in Pb immobilization and transport in lettuce,radish, tomato and Italian ryegrass

Lead (Pb) and other heavy metals represent a great source of concern in agriculture because they may disperse from polluted sources and accumulate in crop organs. This research study was performed with three edible crops and one pasture species (lettuce: Lactuca sativa L. cv. Romana; radish: Raphanus sativus L. var. radicicola; tomato: Lycopersicon lycopersicum L. Karst.; Italian ryegrass: Lolium multiflorum Lam). It was aimed at (1) assessing how species affect Pb distribution among plant organs, (2) determining the extent to which Pb is localized in edible organs, and (3) ascertaining whether it could be possible to distinguish which compounds are responsible for the transport of Pb from one plant organ to another and which compounds are responsible for the accumulation of this metal inside each plant organ. The experiment was conducted in the greenhouse. Plants were grown in plastic pots using a Pb‐spiked sandy soil as substrate. Total Pb concentrations in different plant organs and in soil were determined. Within plants, the maximum accumulation of Pb was found in roots while the remaining part of Pb was mainly located in leaves. Pb L_III edge XANES (X‐ray Absorption Near Edge Spectroscopy) was applied to identify the principal Pb carrier molecules in the different plant organs. The data suggest that in roots Pb immobilization is mainly due to the complexing ability of histidine, which binds the metal and, to a lesser extent, to precipitation of Pb as carbonate. The transport to the upper plant organs is mainly attributed to Pb complexes with organic acids. In stems and leaves, Pb bonding is mainly carboxylic and amino acid‐like, thus confirming the role of these substances in promoting Pb mobility. Thio amino acidic (glutathione and cysteine‐like) Pb complexes, which in this study were only found in stems, can also be held responsible for Pb long‐distance transport from roots to shoots.