Michel-Pierre Faucon

Genetic architecture of zinc hyperaccumulation in Arabidopsis halleri: the essential role of QTL × environment interactions.

SUMMARY This study sought to determine the main genomic regions that control zinc (Zn) hyperaccumulation in Arabidopsis halleri and to examine genotype x environment effects on phenotypic variance. To do so, quantitative trait loci (QTLs) were mapped using an interspecific A. halleri x Arabidopsis lyrata petraea F(2) population. *The F(2) progeny as well as representatives of the parental populations were cultivated on soils at two different Zn concentrations. A linkage map was constructed using 70 markers. *In both low and high pollution treatments, zinc hyperaccumulation showed high broad-sense heritability (81.9 and 74.7%, respectively). Five significant QTLs were detected: two QTLs specific to the low pollution treatment (chromosomes 1 and 4), and three QTLs identified at both treatments (chromosomes 3, 6 and 7). These QTLs explained 50.1 and 36.5% of the phenotypic variance in low and high pollution treatments, respectively. Two QTLs identified at both treatments (chromosomes 3 and 6) showed significant QTL x environment interactions. *The QTL on chromosome 3 largely colocalized with a major QTL previously identified for Zn and cadmium (Cd) tolerance. This suggests that Zn tolerance and hyperaccumulation share, at least partially, a common genetic basis and may have simultaneously evolved on heavy metal-contaminated soils.

Soil influence on Cu and Co uptake and plant size in the cuprophytes Crepidorhopalon perennis and C. tenuis (Scrophulariaceae) in SC Africa

Cuprophytes are plants that mostly occur on Cu-rich soil in SC Africa. Crepidorhopalon perennis is endemic of a single site. C. tenuis has a broader niche, from normal to Cu-rich soil. Both have been considered as Cu-Co accumulators. We examined soil factors controlling heavy metal accumulation and plant fitness in natural populations. Plant mass and element concentrations in plants and soil were determined in 153 samples from five populations of C. tenuis on copper soil (CTC), two on normal soil (CTN) and the single population of C. perennis (CP). Soil in Cu-sites had higher concentrations of Ca, Mg, P, Mn, Zn, Cu, Co. Plants from Cu-sites were larger and had higher Cu and Co content, and lower Mg, Mn and Ca. Cu in shoots was influenced positively by Cu and Mn and negatively by Ca in the soil. Co in shoots was influenced positively by Co and negatively by Mn and Fe in the soil. Shoot mass was influenced positively by Cu and Mn (CT) or by Cu and Co (both species pooled) in the soil. The results suggest that C. tenuis and C. perennis are genuinely cuprophilous species. Large variation in metal accumulation in shoots can be accounted for by synergistic and antagonistic interactions among several heavy metals, yielding specific accumulation patterns in different populations.

Phytostabilisation of Copper-Contaminated Soil in Katanga: An Experiment with Three Native Grasses and Two Amendments

This study evaluates the feasibility of using the grass species Rendlia altera, Monocymbium ceresiiforme, Cynodon dactylon, and amendments (compost and lime) for the phytostabilisation of soils contaminated by Cu in the province of Katanga (Democratic Republic of Congo). Species were grown on control and Cu-contaminated plots (artificially contaminated with 2,500 mg kg−1 Cu) unamended (NA), amended with 4.5 kg compost m−2 or 0.2 kg lime m−2. R. altera was also grown on contaminated plots amended with 22.5 kg compost m−2 or 1 kg lime m−2. Plant survival, growth, and reproduction were monitored for two years. Cu-concentration in leaves of R. altera and M. ceresiiforme were analysed. pH and extractable Cu (0.01 M CaCl2) in soil were analysed in April 2007 and 2008. Results showed that R. altera seems to be the best candidate because of its highest survival on NA, followed by M. ceresiiforme, while liming was necessary to ensure survival of C. dactylon. Lime increased plant reproduction and reduced Cu accumulation in leaves compared to compost. However, higher survival and number of spikes of R. altera obtained in experiment 2 with 22.5 kg compost m−2 suggest that lime x compost interactions should be investigated in further studies.

Prediction of the edaphic factors influence upon the copper and cobalt accumulation in two metallophytes using copper and cobalt speciation in soils

Background and aimsAmong the unique flora on copper and cobalt rich soils, some species are able to hyperaccumulate the Cu and Co in their shoots, however, the unexplained high variations of Cu and Co concentrations in shoots have been highlighted. A good comprehension of the Cu and Co accumulation variations would go through a characterization of the Cu and Co speciation in soils. We examined the covariations of Cu and Co speciation in soils and Cu and Co concentrations in plants.MethodsPlant samples of two species and soil samples (n = 146) were collected in seven pedogeochemically contrasted sites. Cu and Co speciation in soils was modeled by WHAM 6.0.ResultsVariation in copper accumulation in plant shoots were mostly influenced by Cu adsorbed by the Mn and Fe oxides fractions, whereas Co accumulation variations were strongly influenced by Co free and Co adsorbed by the OM and Fe fractions.ConclusionsAvailability of Cu and Co seems to be species-specific and is not explained only by the free Cu and Co content in the soil solution, but also strongly by the part linked to colloidal fractions. Availability of Cu and Co is a complex mechanism, closely related to all the biogeochemical processes which occur in the rhizosphere. Future work should perform experiments in controlled conditions to examine the soil parameters that influence the Cu and Co availability.

Implication of plant-soil relationships for conservation and restoration of copper-cobalt ecosystems

BackgroundChemical soil factors play an important role in generating and maintaining plant diversity. Naturally metal-enriched habitats support highly distinctive plant communities consisting of many rare and endemic species. Species of these plant communities possess remarkable physiological adaptations and are now being considered key elements in the implementation of green technologies aimed at phytoremediation of contaminated soils and post-mined soils. Several studies have emphasised that industrial mineral extraction results in serious damage to ecosystems and serious threats to human health and leads to the extinction of metallophyte species. In the southeastern Democratic Republic of the Congo (DRC), mining activities represent a threat to the long-term persistence of communities located on metalliferous copper and cobalt outcrops and their associated endemic metallophytes, which are currently considered some of the most critically endangered plants in the world.ScopePlant diversity conservation of metal-rich soils must assess soil-plant relationships at different scales (ecosystems, communities, and populations) to define in-situ and ex-situ conservation and restoration projects. This paper proposes a review of soil-plant relationships involved in plant diversity and endemism and their implications for biodiversity conservation and restoration.

Copper and cobalt mobility in soil and accumulation in a metallophyte as influenced by experimental manipulation of soil chemical factors

The influence of Fe oxides, Mn oxides and organic matter (OM) on the Cu and Co mobility in soil and accumulation in the metallophyte Anisopappus chinensis (Ac), as compared with Helianthus annuus (Ha), was experimentally investigated. Growth and accumulation response when increasing the exchangeable Cu and Co concentrations in soil were also investigated. Plants were cultivated on soil where concentrations of Cu, Co, Fe oxides, Mn oxides and OM content were varied according to 36 treatments. The OM supply decreased the Cu mobility and increased the Co mobility, resulting in decreasing the foliar Cu of Ac and increasing the foliar Co of Ha. The Fe oxides supply could increase the Cu accumulation for Ac, but was not verified for Ha. Compared with Ha, Ac increasingly accumulated Cu and Co without negative effect on plant growth while increasing Cu and Co mobility to phytotoxic concentrations. The results revealed promising perspectives for the use of Ac in Cu-contaminated environment phytoremediation applications.

Ullmann reaction through ecocatalysis: insights from bioresource and synthetic potential

We report the elaboration of novel bio-sourced ecocatalysts for Ullmann coupling reaction. Ecocatalysis is based on the recycling of metals issued from phytoremediation or rehabilitation, and an innovative chemical valorization of the subsequent biomass in the field of catalysis. Here, we describe the efficient copper accumulation by plants via phytoextraction and rhizofiltration. These phytotechnologies were revisited to demonstrate a novel potential of these natural resources for the Green Chemistry. Taking advantage of the remarkable ability of the selected plants to accumulate Cu(II) species into their roots or leaves, these latter can be directly used for the preparation of ecocatalysts, called Eco-Cu ®. The formed Eco-Cu ® catalysts are thoroughly characterized via ICP-MS, IR study of pyridine sorption/desorption, TEM, XRD, SM and model reactions, in order to elucidate the chemical composition and catalytic activity of these new materials. Significant differences of properties and activities were observed between Eco-Cu ® and conventional Cu catalysts. Eco-Cu ® appear as highly active catalysts in Ullmann coupling reactions with lower Cu quantity compared to known copper catalysts.

Element Case Studies: Cobalt and Copper

Cobalt is economically considered a critical metal for a variety of technologies. Globally, the most important Co ore deposits occur in the Katangan Copperbelt (Democratic Republic of Congo) where a richness of Cu-Co-tolerant and accumulator plants have developed naturally. Cobalt mining there has resulted in the dissemination of large quantities of waste in the environment and is a major environmental issue. Reduction of environmental risks and Co dispersion can be performed by phytoremediation and/or agromining, using trace-element-tolerant and putative hyperaccumulator plants that originated from the biodiversity of natural Co and Cu-rich habitats. Accumulation of foliar Co to >300 μg g−1 is exceptionally rare globally, being known principally from the Copperbelt of Central Africa. This chapter highlights advances in our knowledge of Co accumulation in plants, examines potential for use of a Co-accumulator in agromining, and defines perspectives for Co agromining by designing multi-functions and services of agroecosystems.

Low Caryopsis Production of the Toothbrush Grass (Microchloa altera) from Katanga (DR Congo) Could Limit the Revegetation of Trace Metal Contaminated Lands by Seeding

1. Direct seeding can be more cost-effective than seedling planting, but the degree of benefit varies widely with many factors. 2. Tree-guarding of seedlings is generally only recommended where there is a threat of herbivory by small animals, such as rabbits. 3. If slender Banksia seedlings are planted in impoverished soils, slow-release native plant fertilizer tablets should be installed adjacent to optimize cost-effectiveness.