L'hyperaccumulation des métaux lourds par les plantes calaminaires: un mécanisme de défense contre les herbivores ?Test de l'hypothèse avec Thlaspi caerulescens et Viola calaminaria

L’hypothèse selon laquelle l’accumulation des métaux lourds par les plantes a évolué comme mécanisme de défense contre les herbivores a été testée avec l’hyperaccumulatrice de zinc Thlaspi caerulescens (Brassicaceae). En utilisant l’écotype métallicole (poussant sur sols métallifères) et l’écotype non métallicole (sols normaux) de T. caerulescens, nos résultats ont conduit à rejeter l’hypothèse de défense par accumulation de métaux: les plantes ont été consommées indépendamment de leur concentration en Zn dans toutes les situations expérimentales examinées (conditions contrôlées, jardin expérimental, populations naturelles). Par contre, les herbivores ont montré une préférence systématique pour les plantes de l’écotype métallicole, quelle que soit leur concentration en Zn. Lorsque l’on mesure les concentrations en métabolites secondaires défensifs (glucosinolates) des écotypes métallicole et non métallicole de T. caerulescens, on constate que les individus d’origine métallicole produisent constitutivement moins de glucosinolates que les individus non métallicoles, tant dans les populations belges que dans les populations françaises. Par ailleurs, sur les sites métallifères où ont évolué les populations métallicoles, on constate à la fois une plus faible pression d’herbivorie sur les plantes (moins de dégâts) et une plus faible densité de gastéropodes que dans les sites normaux. La diminution des défenses chez l’écotype métallicole serait la conséquence d’un relâchement de la pression d’herbivorie sur les sites métallifères. En outre, nous avons montré que la chenille spécialiste d’Issoria lathonia (Nymphalidae) est capable de se développer sur les feuilles riches en Zn de l’accumulatrice de zinc Viola calaminaria (Violaceae) en excrétant efficacement le Zn dans leurs fèces. L’ensemble de nos résultats suggère donc que l’hyperaccumulation des métaux lourds n’a pas évolué en tant que mécanisme de défense contre les herbivores.Doctorat en sciences, Spécialisation biologie végétaleinfo:eu-repo/semantics/nonPublishe

Objectif réussite en BIOLOGIE, un projet qui démarre

Journée d’échanges et de réflexion sur les pratiques pédagogiques de l’Académie Universitaire Wallonie-Bruxellesinfo:eu-repo/semantics/nonPublishe

Field evaluation of cultural cycles for improved cadmium and zinc phytoextraction with Noccaea caerulescens

Background and aimsAdequate cultural cycles for phytoextraction with Noccaea caerulescens have never been investigated, whereas they directly influence biomass production. The aim of this study was to investigate the effects of the season of establishment, the seeding strategy (sowing vs transplantation) and the length of the growing season on biomass production and metal accumulation of N. caerulescens.MethodsA field trial was conducted on an urban wasteland contaminated with trace metals. Two populations with contrasted natural life cycles, one Cd-accumulating metallicolous (Ganges, GAN) and one non-metallicolous from Luxemburg (LUX), were compared in 6 cultural cycles.ResultsDirect sowing in the fall yielded satisfying metal uptake (260 g Cd ha−1 with GAN and 25 kg Zn ha−1 with LUX), though lower than those obtained with transplantation (320 g Cd ha−1 with GAN and 45 kg Zn ha−1 with LUX) due to less biomass production (1.6 vs 3.2 t ha−1). Extending the growing period from 6 to 12 months was mostly beneficial for biennial LUX plants (with 3 times higher Zn uptake), than for annual GAN plants (with 1.5 times higher Cd uptake).ConclusionsThe natural variation in life cycles – annual or biennial – of N. caerulescens should be taken into account when selecting cultivars for phytoextraction.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

La Flore Médicinale Therapeutique ou Toxique ?

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Influence des communautés microbiennes du sol sur la croissance et l'accumulation des métaux in situ par Noccea caerulescens -- Biologie

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Phytoremediation of urban soils contaminated with trace metals using Noccaea caerulescens: comparing non-metallicolous populations to the metallicolous ‘Ganges’ in field trials

Urban soil contamination with trace metals is a major obstacle to the development of urban agriculture as crops grown in urban gardens are prone to accumulate trace metals up to toxic levels for human consumption. Phytoextraction is considered as a potentially cost-effective alternative to conventional methods such as excavation. Field trials of phytoextraction with Noccaea caerulescens were conducted on urban soils contaminated with Cd, Cu, Pb, and Zn (respectively around 2, 150–200, 400–500, and 400–700 μg g−1 of dry soil). Metallicolous (Ganges population) and non-metallicolous (NMET) populations were compared for biomass production and trace metal uptake. Moreover, we tested the effect of compost and fertilizer addition. Maximal biomass of 5 t ha−1 was obtained with NMET populations on some plots. Compared to Ganges— the high Cd-accumulating ecotype from South of France often used in phytoextraction trials— NMET populations have an advantage for biomass production and for Zn accumulation, with an average Zn uptake of 2.5 times higher. The addition of compost seems detrimental due to metal immobilization in the soil with little or no effect on plant growth. In addition to differences between populations, variations of growth and metal accumulation were mostly explained by soil Cd and Zn concentrations and texture. Our field trials confirm the potential of using N. caerulescens for both Cd and Zn remediation of moderately contaminated soils—with uptake values of up to 200 g Cd ha−1 and 47 kg Zn ha−1—and show the interest of selecting the adequate population according to the targeted metal.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Taxonomy of Atlantic Central African orchids 5. A new species of Angraecum sect. Conchoglossum (Orchidaceae, Angraecinae) from Gabon and Cameroon

International audienceRecent field inventories and taxonomic research in Central Africa have resulted in the discovery of many new orchid species. Five specimens of an apparently new Angraecum species were collected in Gabon and Cameroon. They stand out for their hanging habit and short zigzag stem. Morphology of leaves and habit is somewhat comparable to A. cultriforme and A. stolzii, two species from East Africa. Flowers of the novelty share the general morphology of A. pyriforme from which the new species is distinguished by being smaller and with a different lip-spur ratio. Here we show that these five specimens represent a new species, described here as Angraecum lanceolatum. The distinguishing traits include thin lanceolate leaves, convolute distally, with a rhombic lip shape. Dichotomous key to four Central African species of sect. Conchoglossum and a table of the diagnostic characters of the seven related Continental African Angraecum taxa are included here. A preliminary assessment of the conservation status of A. lanceolatum is provided, using the IUCN Red List Categories and Criteria

La phytoremédiation au service de l’agriculture urbaine en Région de Bruxelles-Capitale

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Metal concentration and metal mass of metallicolous, non metallicolous and serpentine Noccaea caerulescens populations, cultivated in different growth media

Aims: Evaluate the genetic and environmental variability of metal concentration and metal mass of Noccaea caerulescens, from metalliferous (MET), non metalliferous (NMET) and serpentine (SERP) soils. Methods: 18 populations were cultivated in 18 different growth conditions, such as a soil mine tailing, soils amended with zinc (Zn), cadmium (Cd) and nickel (Ni) salts (in mixtures or in monometallic salts) and a hydroponic solution with two Zn concentrations. Results: MET populations had Zn concentrations lower than NMET and SERP in the different soils but higher Cd mass (the product of aerial biomass and foliar metal concentration). SERP had the highest Ni concentration and Ni mass values. The addition of Cd or Ni to a Zn-contaminated soil significantly decreases Zn concentration. In hydroponics, MET and NMET had equivalent Zn concentrations but these were three times higher than those obtained in soil experiments. Zn mass of NMET was significantly lower than MET with the latter having Zn mass values largely above those obtained in mine soil. Conclusions: Results showed a large heterogeneity of responses among populations depending on the substrate used, and it was not possible to correctly assign a single population to its accurate origin with only one experiment. Finally, data on metal concentration obtained in culture soils are closer to those in field soils than those from hydroponics so that they could give a more accurate information on the accumulating capacity of Noccaea caerulescens and its use in phytoextraction of metals in field conditions. © 2013 Springer Science+Business Media Dordrecht.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

La phytoremédiation au service du développement durable

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