DNA changes in barley (Hordeum vulgare) seedlings induced by cadmium pollution using RAPD analysis

In recent years, several plant species have been used as bioindicators, and several tests have been developed to evaluate the toxicity of environmental contaminants on vegetal organisms. In this study, barley (Hordeum vulgare L) seedling was used as bioindicator of cadmium (Cd) pollution in the range of 30-120 mgl(-1). Inhibition of root growth and reduction of total soluble protein content in root tips of barley seedlings were observed with the increase of Cd concentrations. The changes occurring in random amplified polymorphic DNA (RAPD) profiles of root tips following Cd treatment included variation in band intensity, loss of normal bands and appearance of new bands compared with the normal seedlings. Additionally, we found that the effect of changes was dose-dependent. These results indicated that genomic template stability (a qualitative measure reflecting changes in RAPD profiles) was significantly affected at the above Cd concentration. Thus, DNA polymorphisms detected by RAPD analysis could be used as an investigation tool for environmental toxicology and as a useful biomarker assay for the detection of genotoxic effects of Cd pollution on plants.     

Cadmium-induced DNA damage and mutations in Arabidopsis plantlet shoots identified by DNA fingerprinting

Random amplified polymorphic DNA (RAPD) test is a feasible method to evaluate the toxicity of environmental pollutants on vegetal organisms. Herein, Arabidopsis thaliana (Arabidopsis) plantlets following Cadmium (Cd) treatment for 26 d were screened for DNA genetic alterations by DNA fingerprinting. Four primers amplified 20-23 mutated RAPD fragments in 0.125-3.0 mg L⁻¹ Cd-treated Arabidopsis plantlets, respectively. Cloning and sequencing analysis of eight randomly selected mutated fragments revealed 99-100% homology with the genes of VARICOSE-Related, SLEEPY1 F-box, 40S ribosomal protein S3, phosphoglucomutase, and noncoding regions in Arabidopsis genome correspondingly. The results show the ability of RAPD analysis to detect significant genetic alterations in Cd-exposed seedlings. Although the exact functional importance of the other mutated bands is unknown, the presence of mutated loci in Cd-treated seedlings, prior to the onset of significant physiological effects, suggests that these altered loci are the early events in Cd-treated Arabidopsis seedlings and would greatly improve environmental risk assessment.     

PCR-RAPD profiling of Fusarium spp. causing guava wilt disease in India

Wilt is a serious disease of the guava crop in India. Fusarium oxysporum f. sp. psidii and F. solani have been reported as causative agents of this disease. In this study, 42 isolates each of F. oxysporum f. sp. psidii and F. solani, were isolated from guava cultivars and characterized by randomly amplified polymorphic DNA (RAPD) method. Thirty RAPD primers were tested in the genome of Fusarium spp. and the number of scorable bands for corresponding primer ranged from 1-8 with an average of 5 bands per individual. DNA band size ranged from 200 bp to 5090 bp. A 0.21 per cent polymorphism was found in individual isolates of F. solani indicating that the 42 isolates were similar. However, a 2.58 percent polymorphism among individual isolates of F. oxysporum f.sp. psidii showed a higher level of genetic diversity. Cluster analysis of the RAPD band patterns clearly separated the isolates of F. oxysporum f.sp. psidii into three clusters. Two clusters were formed with F. solani isolates, showing a higher degree of similarity. Unique fingerprint profiles generated by the PCR-RAPD can be exploited for genetic characterization purposes.     

Underlying mechanisms and effects of hydrated lime and selenium application on cadmium uptake by rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) seedlings

A pot experiment was conducted to investigate the effects of selenium (Se) and hydrated lime (Lime), applied alone or simultaneously (Se+Lime), on growth and cadmium (Cd) uptake and translocation in rice seedlings grown in an acid soil with three levels of Cd (slight, mild, and moderate contamination). In the soil with 0.41 mg kg^?1 Cd (slight Cd contamination), Se addition alone significantly decreased Cd accumulation in the root and shoot by 35.3 and 40.1%, respectively, but this tendency weakened when Cd level in the soil increased. However, Se+Lime treatment effectively reduced Cd accumulation in rice seedlings in the soil with higher Cd levels. The results also showed that Se application alone strongly increased Cd concentration in the iron plaque under slight Cd contamination, which was suggested as the main reason underlying the inhibition of Cd accumulation in rice seedlings. Se+Lime treatment also increased the ability of the iron plaques to restrict Cd uptake by rice seedlings across all Cd levels and dramatically decreased the available Cd concentration in the soil. These results suggest that Se application alone would be useful in the soil with low levels of Cd, and the effect would be enhanced when Se application is combined with hydrated lime at higher Cd levels.     

Chemical behavior of Cd in rice rhizosphere

Chemical behavior of Cd in rice rhizosphere as affected or not by Pb was investigated. The NH4OAc extractable Cd in the rhizosphere was distinctly lower than that in bulk soil. The depletion of Cd in the rhizosphere could not be simply attributed to Cd uptake by rice. The observed phenomena could be attributed to the decreasing pH in the rhizosphere and the complexing capabilities of soluble exudates for Cd. Extractable Cd increased in both the rhizosphere and bulk soil after the addition of Pb, which might be caused by the replacement of Pb for Cd. The extractable Cd in the non-rhizosphere varied with the distance from the root surface, especially within 0-1 mm, which was greatly affected by the combined effects of mass flow, activation and fixation, and had the lowest extractable Cd. Pb addition affected the distribution of extractable Cd in the non-rhizosphere, implying that the affinity of Pb for organic matter was greater than that of Cd. The difference of Cd species between rhizosphere and bulk soil demonstrated that the transformation of exchangeable Cd (EXC-Cd) to OM-Cd (bound to organic matter) and FMO-Cd (bound to iron and manganese oxide) occurred in the rice rhizosphere due to the exudations from the rice root, the activity of microorganisms on the root surface and the activation of Fe and Mn oxides. The interaction between Pb and Cd resulted in the content of EXC-Cd being higher in the presence of Pb, whereas the OM-Cd content was lower in the presence of Pb.     

Cadmium stress alters gene expression of DNA mismatch repair related genes in Arabidopsis seedlings

Cadmium (Cd) is a non essential element, and is a widespread environmental pollutant. Exposure to Cd can result in a variety of adverse health effects in plant and humans. In the current study, Arabidopsis seedlings were used as a bio-indicator of Cd pollution. Seedlings were grown on MS media containing 0-6.0 mg L(-1) Cd for 18 days, and the gene expression patterns were used to link increased Cd exposure with progressive biological effects. Reduction of total soluble protein content in shoots of the Arabidopsis seedlings occurred with increase in Cd concentrations. For the gene expression patterns, seven genes known to be involved in cell division and DNA mismatch repair (MMR) system were investigated by semi-quantitative RT-PCR, and normalized using 18S rRNA gene expression. Expression of the proliferating cell nuclear antigen 2 (atPCNA 2), MutS 3 homolog (atMSH 3) and MutL1 homolog (atMLH1) genes in shoots of Arabidopsis was strongly induced by exposure to 0.75 mg L(-1) Cd, but were repressed by other Cd concentrations whereas exposure to 0.75-6 mg L(-1) of Cd resulted in a decreased expression of atPCNA1, atMSH 2, 6 and 7 genes independently of any observable biological effects, including survival, fresh weight and chlorophyll level of shoots. This work demonstrated that specific gene expression changes could serve as useful molecular biomarkers indicative of Cd exposure and related biological effects.     

DNA integrity of onion root cells under catechol influence

Catechol is a highly toxic organic pollutant, usually abundant in the waste effluents of industrial processes and agricultural activities. The environmental sources of catechol include pesticides, wood preservatives, tanning lotion, cosmetic creams, dyes, and synthetic intermediates. Genotoxicity of catechol at a concentration range 5?×?10^?1–5 mM was evaluated by applying random amplified polymorphic DNA (RAPD) and time-lapse DNA laddering tests using onion (Allium cepa) root cells as the assay system. RAPD analysis revealed polymorphisms in the nucleotidic sequence of DNA that reflected the genotoxic potential of catechol to provoke point mutations, or deletions, or chromosomal rearrangements. Time-lapse DNA laddering test provided evidence that catechol provoked DNA necrosis and apoptosis. Acridine orange/ethidium bromide staining could distinguish apoptotic from necrotic cells in root cells of A. cepa.     

Root growth inhibition and induction of DNA damage in soybean (Glycine max) by chlorobenzenes in contaminated soil

The cytotoxic and genotoxic effects of 1,2,4-trichlorobenzene (TCB), chlorobenzene (CB), and hexachlorobenzene (HCB) on root growth and DNA strand breakage damage of soybean nuclei in the test soil were studied using the comet assay. Results indicated that the root growth was significantly inhibited, and DNA strand breaks and the comet tail in the root tip nuclei were both induced after 48 h exposure with TCB concentrations of 50, 100, 200, 300 microg g(-1) in the soil. DNA strand breakage was more sensitive to the TCB than the root growth. There was a significant dose-response relationship between the TCB exposure and DNA strand breakage in the soybean nuclei. Thus it is possible for DNA strand breakage to be used as a biomarker of soybean exposed to TCB contamination. Significant cytotoxic threshold concentration of the TCB exposure on the root growth inhibition was determined as 61 microg g(-1) in the soil. The toxicity of 100-1,000 microg g(-1) CB and HCB to the soybean seedlings in the soil were not observed after 48 h or longer exposure.     

Root versus canopy uptake of heavy metals by birch in an industrially polluted area: contrasting behaviour of nickel and copper

We investigated root versus canopy uptake of nickel and copper by mountain birch, Betula pubescens subsp. czerepanovi, close to a nickel-copper smelter on the Kola Peninsula, northwest Russia. To distinguish between aerial contamination of leaf surfaces by dust particles and root-derived contamination of leaves by soluble metals, we transplanted seedlings from a control site to clean and metal-contaminated soils and exposed these seedlings both in clean and polluted sites. Patterns of leaf surface contamination and root uptake were similar for nickel and copper; however, nickel but not copper was effectively translocated from roots to shoots and leaves. The majority (80-95%) of nickel and copper found in birch foliage in the heavily contaminated site was due to deposition of dust particles on leaf surfaces; 32-40% of foliar nickel and 9-19% of foliar copper were in water soluble forms. Washing of fresh leaves removed only a minor part of surface contaminants; boiling of unwashed leaves in distilled water for 15 min removed >90% of soluble nickel and copper.     

Growth, ectomycorrhizae and nonstructural carbohydrates of loblolly pine seedlings exposed to ozone and soil water deficit

Loblolly pine (Pinus taeda) seedlings from three full-sib families were exposed to 0, 50, 100 or 150 ppb ozone (O(3)) (5 h/d, 5 d/week for 6 or 12 weeks). Soil water potential was maintained near pot capacity (-0.03 MPa) or soil was allowed to dry to approximately -1.0 MPa and resaturated. Chlorotic mottling and flecking of needles due to O(3) injury were observed for seedlings from all pine families. Soil water deficit lessened the intensity of O(3) symptoms, possibly due to stomatal closure. Exposure to O(3) and soil water deficit each resulted in less seedling volume growth and dry weight, and changed the nonstructural carbohydrate content of seedlings compared with controls. Increasing O(3) concentrations resulted in a linear reduction in foliar starch content but did and affect hexose or sucrose content. Soil water deficit resulted in less starch and soluble sugar contents in above- and below-ground plant parts compared with controls. Soil water deficit did not affect numbers or percentages of roots that formed ectomycorrhizal tips. A linear dose-response relationship between O(3) and ectomycorrhizae was observed. The number of ectomycorrhizal tips/cm long root and the percentage of feeder roots that formed ectomycorrhizae were lower as O(3) concentration increased. Overall, each stress alone caused less seedling growth and carbohydrate content compared with controls, but only O(3) was responsible for suppression of ectomycorrhizae.     

Interaction between cadmium and atrazine during uptake by rice seedlings (Oryza sativa L.)

The uptake of atrazine by rice seedlings (Oryza sativa L.) through plant roots from nutrient solution was investigated in the presence and absence of Cd2+ over an exposure period of four weeks. It was found that both atrazine and Cd2+ were toxic to rice seedlings. Both shoot and root biomasses decreased when the seedlings were exposed to increasing atrazine or Cd2+ concentrations in nutrient solutions. In the absence of Cd2+, a linear relationship was observed between atrazine concentrations in roots/shoots and in external solution, and more atrazine is concentrated in roots than in shoots. When atrazine and Cd2+ concentrations in solution were maintained at mole ratio of 1:1, the accumulation of atrazine by seedlings was less and the seedling biomass was greater than found with other ratios, such as 1:2 or 2:1. Therefore, the formation of the complex between atrazine and Cd2+ reduced the individual toxicities. Analyses of data with the quasi-equilibrium partition model indicated that the atrazine concentrations in rice seedlings and external water were close to equilibrium. In the presence of Cd2+, however, the measured bioconcentration factor (BCF) of atrazine with roots and shoots were considerably greater. The latter findings resulted presumably from the atrazine-Cd2+ complex formation that led to a large apparent BCF.     

The effects of multiple metal contamination on ectomycorrhizal Scots pine (Pinus sylvestris) seedlings

Experiments were conducted to investigate the effects of single and multiple metal contamination (Cd, Pb, Zn, Sb, Cu) on Scots pine seedlings colonised by ectomycorrhizal (ECM) fungi from natural soil inoculum. Seedlings were grown in either contaminated field soil from the site of a chemical accident, soils amended with five metals contaminating the site, or in soil from an uncontaminated control site. Although contaminated and metal-amended soil significantly inhibited root and shoot growth of the Scots pine seedlings, total root tip density was not affected. Of the five metals tested in amended soils, Cd was the most toxic to ECM Scots pine. Field-contaminated soil had a toxic effect on ECM fungi associated with Scots pine seedlings and caused shifts in ECM species composition on ECM seedlings. When compared to soils amended with only one metal, soils amended with a combination of all five metals tested had lower relative toxicity and less accumulation of Pb, Zn and Sb into seedlings. This would indicate that the toxicity of multiple metal contamination cannot be predicted from the individual toxicity of the metals investigated.     

Ecological risk assessment using RAPD and distribution pattern of a rare and endangered species

Environmental and ecological risk assessment always provide useful evidence for characterisation and conservation of the rare and endangered species, e.g. seven-son flower (Heptacodium miconioides Rehd.). Seven-son flower is a deciduous arbor species, but endangered, with a restricted distribution in the subtropical forests of China. Genetic risk assessment of 56 samples of the flower from nine main populations in Zhejiang (China) was carried out by using the RAPD analysis. This was to study the ecological characteristics, spatial distribution and genetic features of the seven-son flower communities and establish a feasible conservation plan. Twenty-one primers screened from 50 yielded 119 RAPD bands with 72 polymorphic products and 60.50% of total bands. The genetic variation was found to be partitioned mainly among rather than within populations. Percentages of genetic diversity among populations were quantified by Shannon index and the Nei's gene diversity coefficient. AMOVA also demonstrated that these relict populations were highly differentiated. The high level of population variation observed is in contrast to that expected for a primarily outcrossed woody perennial plant, and suggests that there may be a degree of inbreeding. The dendrogram constructed from genetic distances through UPGMA method based on Nei's coefficients shows two groups among nine population clusters, which is further supported by a principle components analysis (PCA) of RAPD phenotypic data. The analysis showed that the biologic characteristics and habitat fragmentation were the reasons of the great genetic variation among populations. Some strategies of its genetic diversity conservation were proposed in the fragmented habitats based on its genetic structure and its biological characteristics in this study.     

光合细菌改善Cd、Pb及呋喃丹污染土壤的微生物群落DNA序列多样性的研究

应用DNA随机扩增多态性(RAPD)分子标记技术研究了光合细菌(PSB)对Cd、Pb及呋喃丹污染土壤的微生物群落DNA序列多样性的影响.结果表明,Cd、Pb及呋喃丹单一污染或3者复合污染土壤的微生物群落DNA序列的丰富度相对对照土样(S0)都有不同程度的增加,受Cd、Pb或呋哺丹污染,可能会引起土壤微生物群落DNA序列...     

Cadmium (Cd) distribution and contamination in Chinese paddy soils on national scale

Rice is a staple food by an increasing number of people in China. As more issues have arisen in China due to rice contaminated by cadmium (Cd), Cd contamination in arable soils has become a severe problem. In China, many studies have examined Cd contamination in arable soils on a national scale, but little studies have focused on the distribution of Cd in paddy fields. This study explored the spatial pattern of Cd in paddy soils in China, made a preliminary evaluation of the potential risk, and identified the most critically contaminated regions based on the domestic rough rice trade flow. The results showed that Cd concentrations in paddy soils in China ranged from 0.01 to 5.50 mg/kg, with a median value of 0.23 mg/kg. On average, the highest Cd concentrations were in Hunan (0.73 mg/kg), Guangxi (0.70 mg/kg), and Sichuan (0.46 mg/kg) provinces. Cd concentrations in paddy soils in central and western regions were higher than those in eastern regions, especially the southeastern coastal regions. Of the administrative regions, Cd standard exceedance rate was 33.2 %, and the heavy pollution rate was 8.6 %. Regarding to Cd of paddy soil, soil environmental quality was better in Northeast China Plain than in Yangtze River Basin and southeastern coastal region. Mining activities were the main anthropogenic pollution source of Cd in Chinese paddy soil. Based on rice trade, more of the Chinese population would be exposed to Cd through intake of rice produced in Hunan province. Certain regions that output rice, especially Hunan province, should be given priority in the management and control of Cd contamination in paddy soil.     

The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings

A historically multi-metal contaminated soil was amended with biochars produced from different parts of rice plants (straw, husk and bran) to investigate how biochar can influence the mobility of Cd, Zn, Pb and As in rice seedlings (Oryza sativa L.). Rice shoot concentrations of Cd, Zn and Pb decreased by up to 98%, 83% and 72%, respectively, due to biochar amendment, though that of As increased by up to 327%. Biochar amendments significantly decreased pore water concentrations (C_pw) of Cd and Zn and increased that of As. For Pb it depended on the amendment. Porewater pH, dissolved organic carbon, dissolved phosphorus, silicon in pore water and iron plaque formation on root surfaces all increased significantly after the amendments. The proportions of Cd and Pb in iron plaque increased by factors 1.8-5.7 and 1.4-2.8, respectively; no increase was observed for As and Zn. Straw-char application significantly and noticeably decreased the plant transfer coefficients of Cd and Pb. This study, the first to investigate changes in metal mobility and iron plaque formation in rice plants due to amending a historically contaminated soil with biochar, indicates that biochar has a potential to decrease Cd, Zn and Pb accumulations in rice shoot but increase that of As. The main cause is likely biochar decreasing the C_pw of Cd and Zn, increasing the C_pw of As, and increasing the iron plaque blocking capacity for Cd and Pb.     

Foliar application of aspartic acid lowers cadmium uptake and Cd-induced oxidative stress in rice under Cd stress

Environmental Science and Pollution Research - Cadmium (Cd) contamination of farmland soils is a widespread problem around the globe, and rice (Oryza sativa L.) tends to accumulate more Cd and is...     

Effect of culturing temperatures on cadmium phytotoxicity alleviation by biochar

Biochar produced from rice straw at 400 °C (RS400) was prepared to determine its alleviating effect on Cd phytotoxicity to wheat seedlings under different cultivation temperatures and pH. A hydroponic system (pH 4.3) and a loam soil slurry system were designed to respectively simulate acidic and neutral soil condition, and cultivation at increasing temperatures (20, 25, and 30 °C) were performed to evaluate the greenhouse effect. The root and shoot elongation and the Cd concentration in root and solution were measured; furthermore, batch experiments for Cd adsorption were undertaken. An increasing inhibition of the root by Cd addition was observed at increasing temperatures. The inhibition rate was 50.50 and 20.80% in hydroponic system and slurry system at 25 °C, respectively; however, the corresponding inhibition rates of root were significantly decreased to 25.5 and 3.5% with addition of RS400. This is mainly attributed to the reduction of Cd migration into the roots by RS400, which decreased Cd bioavailability. The mechanism behind the reduced Cd bioavailability is attributed to the Cd adsorption and the strong buffering capacity of acidity by RS400. Therefore, biochar could be a potential amendment for the remediation of Cd-contaminated soil even at increasing culturing temperatures.

     

Effects of aqueous Moringa oleifera leaf extract on growth performance and accumulation of cadmium in a Thai jasmine rice—Khao Dawk Mali 105 variety

Environmental Science and Pollution Research - The contamination of paddy fields and rice grains by cadmium (Cd) adversely affects human health. Thus, many approaches have been proposed to reduce...     

Phytoextraction of cadmium by rice (Oryza sativa L.), soybean (Glycine max (L.) Merr.), and maize (Zea mays L.)

Selecting a phytoextraction plant with high Cd-accumulating ability based on the plant's compatibility with mechanized cultivation techniques may yield more immediately practical results than selection based on high tolerance to Cd. Rice (Oryza sativa L., cv. Nipponbare and Milyang 23), soybean (Glycine max [L.] Merr., cv. Enrei and Suzuyutaka), and maize (Zea mays L., cv. Gold Dent) were grown on one Andosol and two Fluvisols with low concentration of Cd contamination ranging from 0.83 to 4.29 mg Cd kg(-1), during 60 days in pots (550 mL) placed in a greenhouse. Shoot Cd uptake was as follows: Gold Dent相似文献