Lead-induced DNA damage in Vicia faba root cells: Potential involvement of oxidative stress

Genotoxic effects of lead (0–20 µM) were investigated in whole-plant roots of Vicia faba L., grown hydroponically under controlled conditions. Lead-induced DNA damage in V. faba roots was evaluated by use of the comet assay, which allowed the detection of DNA strand-breakage and with the V. faba micronucleus test, which revealed chromosome aberrations. The results clearly indicate that lead induced DNA fragmentation in a dose-dependant manner with a maximum effect at 10 µM. In addition, at this concentration, DNA damage time-dependently increased until 12 h. Then, a decrease in DNA damages was recorded. The significant induction of micronucleus formation also reinforced the genotoxic character of this metal. Direct interaction of lead with DNA was also evaluated with the a-cellular comet assay. The data showed that DNA breakages were not associated with a direct effect of lead on DNA. In order to investigate the relationship between lead genotoxicity and oxidative stress, V. faba were exposed to lead in the presence or absence of the antioxidant Vitamin E, or the NADPH-oxidase inhibitor dephenylene iodonium (DPI). The total inhibition of the genotoxic effects of lead (DNA breakage and micronucleus formation) by these compounds reveals the major role of reactive oxygen species (ROS) in the genotoxicity of lead. These results highlight, for the first time in vivo and in whole-plant roots, the relationship between ROS, DNA strand-breaks and chromosome aberrations induced by lead

Effect of Calcium Deficiency on Growth and Leaf Acid Soluble Proteins of Tomato

The effects of temporary Ca (Ca) calcium deficiency lasting 2, 3, 4 or 5 d were investigated on tomato plants at the 6-leaf stage, grown hydroponically under controlled conditions. With 2, 3 or 4 d of Ca deficiency, the dry weight of the tomato leaves, shoots or roots was not different from control. A significant decrease in tomato growth, of up to 70%, appeared on the fifth day. Some visual symptoms were observed on the tomato leaves. The phenomenon concerned was an irreversible mechanism that led to plant death after 12 d, even when Ca was added to the root medium after 2, 3, 4 or 5 d. This is the first report of such a rapid and drastic effect of an essential macronutrient. Moreover, Ca content in leaves during root deprivation showed a decrease in all plants, related to a remobilization toward the apex. Ca could be considered as a partly mobile element: the observation of the youngest leaf limbs by transmission electronic microscopy after 4 d of treatment showed disorganized tissues in a necrotic zone, due to wall impairment related to C deficiency. During temporary Ca deficiency, acid soluble proteins were analyzed in leaves (SDS PAGE electrophoresis / Maldi-TOF). After 4 d of Ca deficiency, protein induction in young leaves was revealed. Three proteins were identified as pathogenesis related proteins (PR-1, PR-3, PR-7) and a threonine deaminase precursor was also found. It was also the first time that pathogenesis related (PR) protein appearance has been shown to be related to Ca deficiency. The PR proteins are generally elicited by pathogen attack. This phenomenon seems to be calcium dependent because other mineral stresses, such as potassium (K) deficiency or sodium (Na) excess, did not reveal acid soluble protein changes. The retranslocation of Ca to young tissue could entail eliciting effects via wall fragments leading to a plant response similar to the response to pathogen attac

Trace determination of linear alkylbenzene sulfonates: application in artificially polluted soil-carrots system

Surfactants are widely used in household and industrial products. The risk of incorporation of linear alkylbenzene sulfonates (LAS)from biosolids, wastewater, and fertilizers land application to the food chain is being assessed at present by the European Union. In the present work, a complete analytical method for LAS trace determination has been developed and successfully applied to LAS (C10–C13) uptake in carrot plants used as model. These carrots were grown in soil with the trace organics compounds added directly into the plant containers in pure substances form. LAS trace determination (μg kg−1 dry matter) in carrots samples was achieved by Soxtec apparatus and high-performance liquid chromatography-fluorescence detection. The methodology developed provides LAS determination at low detection limits (5 μg kg−1 dry matter) for carrot sample (2 g dry matter) with good recoveriesate (>90%). Transfer of LAS has been followed into the various parts of the carrot plant. LAS are generally found in the carrot leaves and percentage transfer remains very low (0.02%)

Sand to Root Transfer of PAHs and PCBs by Carrots Grown on Sand with Pure Substances and Biosolids Amended Sand

A study on behaviour of trace organic compounds (Polycyclic Aromatic Hydrocarbons, PAH, and Polychlorinated Biphenyls, PCB) in a sand-plant system has been carried out, with the reclamation of wastewater treatment plant biosolids for agriculture in mind. Carrot plants (Daucus carota) were grown on soilless culture (sand), to provide optimal transfer conditions, in plant containers inside a temperature regulated greenhouse. There were two types of experiment. The trace organic compounds have initially been introduced as pure substances. A second experiment has been carried out under the same conditions, but using biosolids. Plant development has been unaffected by the presence of the pure substances and the biosolids. The transfer of the trace organic compounds has been followed in the peel, the core and the leaves of the carrot plants. Results obtained are expressed as fluxes of the trace organic compounds into the plant. The results clearly show that trace organic compounds accumulate in the carrot peel

Can we predict community-wide effects of herbicides from toxicity tests on macrophyte species?

Macrophyte communities play an essential role in the way freshwater ecosystems function. It is thus of great concern to understand how environmental factors, especially anthropogenic ones, influence their composition and diversity. The aim of this study was to examine whether the effects of a herbicide mixture (50% atrazine, 35% isoproturon, 15% alachlor) on single macrophyte species can be used to predict its impact at a community level. In a first experiment we tested the sensitivity of six species (Azolla filiculoides, Ceratophyllum demersum, Elodea canadensis, Lemna minor, Myriophyllum spicatum and Vallisneria spiralis) grown separately and exposed to 0.6–600 gL−1 of the herbicide mixture. In a second experiment, conducted in microcosms, we tested the effects of herbicides on macrophyte assemblages composed of the same six species exposed to 0, 6 or 60 gL−1 of the herbicide mixture. Species grown separately exhibited growth inhibition at 60 and 600 gL−1. At 600 gL−1 the sensitivity differed significantly between species. V. spiralis was the most resistant species, C. demersum, M. spicatum and E. canadensis exhibited intermediate sensitivities, and A. filiculoides and L. minor were the most sensitive species. In microcosms, community biomass and Shannon evenness index were reduced after 8 weeks at 60 gL−1. Communities also exhibited changes in their composition: the relative and absolute abundance of C. demersum increased at 6 gL−1, while the relative abundance of V. spiralis increased at 60 gL−1. These results are in agreement with the individual responses of these species to the herbicides. It is therefore concluded that short-term effects of herbicides on simple macrophyte communities can be predicted from the sensitivity of individual species. However, further investigations are required to examine whether longer term effects can be predicted as well, especially in more complex communities

Herbicide effects on freshwater benthic diatoms: Induction of nucleus alterations and silica cell wall abnormalities

Benthic diatoms are well known bio-indicators of river pollution by nutrients (nitrogen and phosphorus). Biological indexes, based on diatom sensitivity for non-toxic pollution, have been developed to assess the water quality.Nevertheless, they are not reliable tools to detect pollution by pesticides. Many authors have suggested that toxic agents, like pesticides, induce abnormalities of the diatom cell wall (frustule). High abnormal frustule abundances have been reported in natural diatom communities sampled in streams contaminated by pesticides. However, no direct link was found between the abundances of abnormal frustules in these communities and the pesticide concentrations in stream water. In the present study, a freshwater benthic diatomcommunity, isolated fromnatural biofilm and cultured under controlled conditions, was treated with a known genotoxic herbicide, maleic hydrazide (MH). Cells were exposed to three concentrations of MH (5×10−6, 10−6, 10−7 M) for 6 h followed by a 24 h-recovery time. After MH treatments, nucleus alterations were observed: abnormal nucleus location, micronucleus, multinuclear cell or disruption of the nuclear membrane. A dose-dependent increase of nuclear alterations was observed. The difference between the control (9.65 nuclear alterations per 1000 cells observed (9.65‰), S.D. = 4.23) and the highest concentrations (29.40‰, S.D. = 8.49 for 10−6Mand 35.96‰, S.D. = 3.71 for 5×10−6 M)was statistically significant (Tukey test, P < 0.05). Diatoms also exhibited frustules with deformed morphology and abnormal ornamentation. Significantly increased abundances of abnormal frustules were observed for the highest concentrations (10−6 and 5×10−6 M; Tukey test, P < 0.05). These two parameters tended to increase together (Pearson correlation = 0.702, P < 0.05). The results suggest that the induction of abnormal frustules could be associated with the genotoxic effects of MH. The alterations observed could be related to the effects of MH on the synthesis of the proteins involved in frustule formation or in the regulation of the cytoskeleton of the diatom cells

Lead-induced genotoxicity to Vicia faba L.roots in relation with metal cell uptake and initial speciation

Formation of organometallic complexes in soil solution strongly influence metals phytoavailability. However, only few studies deal with the influence of metalspeciation both on plant uptake and genotoxicity. In the present study, Viciafaba seedlings were exposed for 6 h in controlled hydroponic conditions to 5 μM of lead nitrate alone and chelated to varying degrees by different organic ligands. Ethylenediaminetetraacetic acid and citric acid were, respectively, chosen as models of humic substances and low weight organic acids present in natural soil solutions. Visual Minteq software was used to estimate free lead cations concentration and ultimately to design the experimental layout. For all experimental conditions, both micronucleus test and measure of leaduptake by plants were finally performed. Chelation of Pb by EDTA, a strong chelator, dose-dependently increased the uptake in V. faba roots while its genotoxicity was significantly reduced, suggesting a protective role of EDTA. A weak correlation was observed between total lead concentration absorbed by roots and genotoxicity (r2=0.65). In contrast, a strong relationship (r2=0.93) exists between Pb2+ concentration in exposure media and genotoxicity in the experiment performed with EDTA. Citric acid induced labile organometallic complexes did not demonstrate any significant changes in leadgenotoxicity or uptake. These results demonstrate that metalspeciation knowledge could improve the interpretation of V. fabagenotoxicity test performed to test soil quality

Thidiazuron-induced shoot organogenesis from mature leaf explants of scented Pelargonium capitatum cultivars

Shoot organogenesis from mature leaf tissues of two scented Pelargonium capitatum cultivars, ‘Attar of Roses’ and ‘Atomic Snowflake’, grown in the greenhouse, were optimized in the presence of thidiazuron (TDZ). The protocol involved preculture of leaf sections on basal Murashige and Skoog (MS) medium supplemented with 10 lM TDZ, 4.4 lM of 6-benzyladenine (BA) and 5.4 lM a-naphtaleneacetic acid (NAA) for a period of 2 weeks and followed by subculture of explants to a fresh medium containing 4.4 lM BA and 5.4 lM NAA. Frequency of regeneration reached approximately 93% for both cultivars, with the induction of more than 100 shoots per explant. Regenerated plantlets were rooted on half-strength MS medium supplemented with 4.4 mM sucrose and 8.6 lM of Indole-3-acetic acid (IAA). All regenerated shoots from both cultivars developed roots when transferred to organic soil mix, acclimatized, and successfully transferred to greenhouse conditions. When regenerated shoots were transferred to hydroponic conditions, frequency of survival was 76.2 and 61.9% for ‘Attar of Roses’ and ‘Atomic Snowflake’, respectively

Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize

A physico-chemical process has been developed to transform and enhance lignocellulosic waste in liquid humic extracts: humic-like substances (HLS). The aim of this study was to determine the effects of HLS on plant physiology in order to consider their agricultural use as organic fertilizers. The effects of HLS were evaluated on maize seed germination, and their impact on growth, development and mineral nutrition was studied on maize plants cultivated under hydroponic conditions. The experimental results showed that HLS do not increase the percentage and rate of germination but enhance the root elongation of seeds thus treated. Positive effects were also observed on the whole plant growth as well as on root, shoot and leaf biomass. These effects can be related to the high water and mineral consumption of plants undergoing this treatment. The high water efficiency indicated that such plants produce more biomass than non-treated plants for the same consumption of the nutrient solution. Furthermore, the use of HLS induced a flowering precocity and modified root development suggesting a possible interaction of HLS with developmental processes. Considering the beneficial effect of HLS on different stages of plant growth, their use may present various scientific and economic advantages. The physico-chemical transformation of sawdust is an interesting way of enhancing organic waste materials

Assessment of the genotoxicity of Cu and Zn in raw and anaerobically digested slurry with the Vicia faba micronucleus test

Genotoxicity of Cu and Zn was assessed by use of the micronucleus (MN) test on Vicia faba roots. Plants were exposed to various leachates of rawand anaerobically digested pig slurry, with maximum total concentrations of 200MCu and 600MZn. The results indicated stabilisation of the organic matter during anaerobic digestion of the slurry and bioconversion of some phytotoxic organic compounds (e.g. phenols or p-cresol), but did not showa relationship between Cu and Zn concentrations and MN frequency. Exposure of Vicia plants to binary inorganic solutions of Cu and Zn (CuSO4/ZnSO4, 1:3) showed a significant micronucleus induction at concentrations of 40M Cu and 120M Zn and higher. When MN frequency was plotted against dissolved Cu (<0.45m), applied as slurry or as CuSO4, a single curve was obtained. At concentrations lower than 10M, modulation of the genotoxic effect of Cu was found. At concentrations up to 150M,MNinduction increased significantly, while phytotoxic symptoms appeared at higher concentrations