Mercè Llugany

Arsenic and heavy metal contamination of soil and vegetation around a copper mine in Northern Peru

Abstract At present, very little information is available on either the environmental impact or the biogeochemistry of mine sites in Latin America. Here we present preliminary results on contamination of soils and plants around a copper mine in the Andes of Northern Peru. Plants and soils were sampled at six sites ranging from low (S1) to high phytotoxicity (S6); samples were analysed for concentrations of As and heavy metals. Stepwise multiple regression analysis was used in order to determine the soil factors that significantly influenced As and metal availability. High As and Cu concentrations in soil extracts (ammonium acetate-EDTA), in addition to low pH and high Al availability, seem to be the most important soil factors that limit plant performance around the mice. A high organic matter content favoured Cu and Al extractability. Nevertheless, phytotoxicity was more intense at sites with low organic matter concentrations. Unusually high concentrations of As and metal concentrations were detected in leaves of some species (e.g. in Bidens cynapiifolia up to 1430 μg/g dry wt. As, 437 Zn, 620 Cu, 6510 Al and 5.7% Fe) while others (e.g. Eriochloa ramosa) more effectively restricted metal transport to the shoots. These plant species seem interesting for future investigations on both metal tolerance mechanisms and revegetation of contaminated soils at the numerous mine sites located at high altitudes in equatorial regions.

Copper in plant species in a copper gradient in Catalonia (North East Spain) and their potential for phytoremediation

The accumulation of Cu in roots and shoots of 32 plant species growing on soils with a wide range of Cu concentrations (30–18 500 μg g−1 total soil Cu) located in Collserola Mountain (Barcelona, Spain) was analysed. High Cu availability decreased the species diversity in the Hyparrhenietum hirto-pubescentis, the natural plant association at the study sites. Shoot and root Cu concentrations in relation to extractable soil Cu concentrations were used for the evaluation of the Cu resistance strategy in the different species. Saturation of Cu accumulation in roots was observed in most species. Hyparrhenia hirta was the most efficient shoot excluder, while the linear increase of shoot Cu with the Cu soil concentration exhibited the highest slope in Hirschfeldia incana. Most species accumulated more Cu in roots than in shoots. High shoot/root Cu ratios were only found in the highly Cu-resistant Hirschfeldia incana, in the resistant or moderately resistant Spartium junceum and Reseda sp. (R. lutea and R. phyteuma), and in the much less resistant Ononis natrix. Only two species, Hirschfeldia incana and Sedum sediforme were able to support the extreme Cu-toxicity conditions on soils with 5000–16 800 μg g−1 extractable Cu. Among the grass species tested Hyparrhenia hirta was the most Cu-resistant species (up to 1950 μg g−1 extractable soil Cu). The potential usefulness of these pseudometallophytes for phytoremediation of Cu-contaminated soils is discussed.

Different mechanisms account for enhanced copper resistance in Silene armeria ecotypes from mine spoil and serpentine sites

The resistance to excess Cu was evaluated in solution culture in three ecotypes of Silene armeria from different origin, a garden soil (Cadriano), a serpentine site (Prinzera) and a Cu mine spoil (Vigonzano). Root elongation and viability staining of root tip cells were used as indicators for Cu resistance. The Cu resistance increased in the order Cadriano <Prinzera<Vigonzano. Renewal of the root cap in Prinzera and enhanced border cell production in Vigonzano in response to excess Cu provided a more efficient protection of the root tip meristem than in Cu sensitive Cadriano. The enhanced Cu resistance in Prinzeracould not be attributed to high soil Cu acting as a natural selection factor at the serpentine site. In PrinzeraCu exclusion from roots and shoots probably was a consequence of root impermeabilization causing reduced radial water and ion flux in roots. In contrast, the high Cu resistance in the mine spoil ecotype, Vigonzano, was due to both reduced Cu uptake and higher tissue tolerance of Cu.

Callose production as indicator of aluminum toxicity in bean cultivars

Abstract The response of seven cultivars of beans to aluminum (Al) stress was assessed by using root elongation rate and callose accumulation in 5 mm root tips as early markers of injury. Bean seedlings were grown in acid nutrient solution (pH 4.5) and exposed to 0, 20, and 50 μM Al for 24 h. Root elongation was recorded at frequent intervals and callose accumulation was determined spectrofluorometrically. Based on the root elongation rate, Strike and Contender were Al‐sensitive and F‐15 and Superba were the most Al‐tolerant cultivars. The cultivars Hilds maxi, Hinrichs riesen, and Saxa showed an intermediate behavior. Callose synthesis positively correlated with internal Al concentration and negatively correlated with root elongation rate. Both callose accumulation and root elongation rate were useful in classifying the bean cultivars for aluminum tolerance, but root elongation rate was a more sensitive parameter. Root callose deposition can serve as an early marker for Al toxicity and tolerance in beans.

Short‐term effects of pH and aluminium on mineral nutrition in maize varieties differing in proton and aluminium tolerance

Abstract In short‐term (24 h) nutrient solution experiments, the influence of different proton (pH 6.0 and pH 4.3) and aluminium (Al) (0, 20, and 50 μM) concentrations on root and coleoptile elongation, dry weight, and the uptake of selected mineral nutrients was studied in maize (Zea mays L.) varieties that differ in acid soil tolerance under field conditions. The acid‐soil‐tolerant maize varieties, Adour 250 and C525M, proved to be hydrogen (H+) ion sensitive, but Al tolerant, while the acid soil tolerant variety BR201F was H+ tolerant but Al sensitive. The acid soil sensitive variety HS 7777 was affected by both H+ and Al toxicity. The proton‐induced inhibition of root elongation was closely related to the proton‐induced decrease of the specific absorption rates (SAR) of boron (B), iron (Fe), magnesium (Mg), calcium (Ca), and phosphorus (P). In contrast, only the specific absorption rate of B (SARB) was significantly correlated to the Al‐induced inhibition of root elongation. It is concluded, that alte...

Influence of the Ca/Mg ratio on Cu resistance in three Silene armeria ecotypes adapted to calcareous soil or to different, Ni- or Cu-enriched, serpentine sites

This hydroponic study addresses the influence of low (0.3) and high (4.0) Ca/Mg molar ratios on Cu resistance of Silene armeria ecotypes from different habitats: a calcareous soil (ecotype Cadriano), a Ni-rich serpentine site (ecotype Prinzera), and an acid Cu-mine spoil soil containing serpentinite (ecotype Vigonzano). Under control conditions, without excess Cu, only Cadriano was negatively affected by the low Ca/Mg ratio. Under both low and high Ca/Mg ratios Cu resistance followed the order Vigonzano more more than Prinzera > Cadriano. More efficient Cu exclusion accounted for enhanced Cu resistance in Prinzera. The low Ca/Mg ratio increased Cu uptake in Prinzera but did not worsen toxicity effects; i.e. the plants had higher internal Cu effect concentrations. In Vigonzano Cu resistance was enhanced by the low Ca/Mg ratio. This was due only in part to better Cu exclusion. Magnesium-induced tolerance to higher Cu tissue concentrations appears to be in ecotypes from serpentine and acid mine spoils, but not in plants from calcareous soil, the exposure to low Ca/Mg ratio favours internal detoxification of Cu by means of more efficient chelation and compartmentation.

Endogenous jasmonic and salicylic acids levels in the Cd-hyperaccumulator Noccaea ( Thlaspi ) praecox exposed to fungal infection and/or mechanical stress

Key messageSensitivity toErysipheinNoccaea praecoxwith low metal supply is related to the failure in enhancing SA. Cadmium protects against fungal-infection by direct toxicity and/or enhanced fungal-induced JA signaling.AbstractMetal-based defense against biotic stress is an attractive hypothesis on evolutionary advantages of plant metal hyperaccumulation. Metals may compensate for a defect in biotic stress signaling in hyperaccumulators (metal-therapy) by either or both direct toxicity to pathogens and by metal-induced alternative signaling pathways. Jasmonic acid (JA) and salicylic acid (SA) are well-established components of stress signaling pathways. However, few studies evaluate the influence of metals on endogenous concentrations of these defense-related hormones. Even less data are available for metal hyperaccumulators. To further test the metal-therapy hypothesis we analyzed endogenous SA and JA concentrations in Noccaea praecox, a cadmium (Cd) hyperaccumulator. Plants treated or not with Cd, were exposed to mechanical wounding, expected to enhance JA signaling, and/or to infection by biotrophic fungus Erysiphecruciferarum for triggering SA. JA and SA were analyzed in leaf extracts using LC–ESI(−)–MS/MS. Plants without Cd were more susceptible to fungal attack than plants receiving Cd. Cadmium alone tended to increase leaf SA but not JA. Either or both fungal attack and mechanical wounding decreased SA levels and enhanced JA in the Cd-rich leaves of plants exposed to Cd. High leaf Cd in N. praecox seems to hamper biotic-stress-induced SA, while triggering JA signaling in response to fungal attack and wounding. To the best of our knowledge, this is the first report on the endogenous JA and SA levels in a Cd-hyperaccumulator exposed to different biotic and abiotic stresses. Our results support the view of a defect in SA stress signaling in Cd hyperaccumulating N. praecox.

Cadmium exclusion a key factor in differential Cd-resistance in Thlaspi arvense ecotypes

Differences in Cd accumulation and Cd tolerance between Thlaspi arvense ecotype Aigues Vives (AV) from a commercial grower in South France and ecotype Jena collected in the polluted urban area of Jena (Germany) were reported here. Ecotype Jena exhibited considerable Cd-tolerance. Shoot and root masses were unaffected and root elongation was even enhanced by exposure to 50 μM Cd. In contrast, growth of ecotype AV was severely affected by this Cd treatment. Ecotype Jena was much more efficient in excluding Cd from both roots and shoots than ecotype AV. Despite the efficient restriction of Cd transport from roots to shoots in Jena, this ecotype maintained high root to shoot transport of Zn and Fe under Cd exposure. Cd supply strongly decreased the activities of antioxidant enzymes in AV, while in the Cd resistant Jena these activities either remained unaffected (SOD, APX) or were increased (CAT) by Cd supply. In conclusion, naturally selected Cd-tolerance in Thlaspi arvense is due to efficient Cd exclusion. The mechanisms underlying exclusion of Cd from the shoots seem Cd-specific yet they did not affect the homeostasis of Fe and Zn in the shoots.

Transfer of selected mineral nutrients and trace elements in the host–hemiparasite association, Cistus–Odontites lutea, growing on and off metal‐polluted sites

The role of a hemiparasitic life-style in plant resistance to toxic trace elements in polluted soils is unclear. Restriction of metal uptake by the host, restriction of metal transfer from host to parasite, or transformation of metals into a less toxic form may play a role. This study analysed the transfer of selected mineral elements from soil to host (Cistus spp.) and from host to hemiparasite (Odontites lutea) at locations with different metal burdens: a Cu-rich serpentine site, Pb-Ba mine spoil and an unpolluted soil. Highest soil-to-host transfer factors for K, Mg, Ca, Zn, Cu and Pb were observed on the unpolluted soil. Statistically significant differences among locations of host-to-parasite transfer factors were only found for Ca and Pb. Restriction of transfer of unfavourable Ca/Mg ratios, characteristic at the serpentine site, and of high Pb and Zn concentrations at the Pb-Ba mine occurred mainly at the soil-host, and not at the host-parasite, level. Odontites lutea was able to withstand enhanced Zn and Pb concentrations and low Fe/Cu ratios in shoot tissue without developing toxicity symptoms. This could be caused by specific metal resistance mechanisms in this hemiparasite and/or the transformation and transfer of these metals into a less toxic form by the metal-tolerant host.

Differential activation of genes related to aluminium tolerance in two contrasting rice cultivars.

Rice (Oryza sativa) is a highly Al-tolerant crop. Among other mechanisms, a higher expression of STAR1/STAR2 (sensitive to Al rhizotoxicity1/2) genes and of Nrat1 (NRAMP Aluminium Transporter 1), and ALS1 (Aluminium sensitive 1) can at least in part be responsible for the inducible Al tolerance in this species. Here we analysed the responses to Al in two contrasting rice varieties. All analysed toxicity/tolerance markers (root elongation, Evans blue, morin and haematoxylin staining) indicated higher Al-tolerance in variety Nipponbare, than in variety Modan. Nipponbare accumulated much less Al in the roots than Modan. Aluminium supply caused stronger expression of STAR1 in Nipponbare than in Modan. A distinctively higher increase of Al-induced abscisic acid (ABA) accumulation was found in the roots of Nipponbare than in Modan. Highest ABA levels were observed in Nipponbare after 48 h exposure to Al. This ABA peak was coincident in time with the highest expression level of STAR1. It is proposed that ABA may be required for cell wall remodulation facilitated by the enhanced UDP-glucose transport to the walls through STAR1/STAR2. Contrastingly, in the roots of Modan the expression of both Nrat1 coding for a plasma membrane Al-transporter and of ALS1 coding for a tonoplast-localized Al transporter was considerably enhanced. Moreover, Modan had a higher Al-induced expression of ASR1 a gene that has been proposed to code for a reactive oxygen scavenging protein. In conclusion, the Al-exclusion strategy of Nipponbare, at least in part mediated by STAR1 and probably regulated by ABA, provided better protection against Al toxicity than the accumulation and internal detoxification strategy of Modan mediated by Nrat1, ALS1 and ARS1.