Douglas fir (pseudotsuga menziesii) plantlets responses to as, PB, and sb-contaminated soils from former mines

Abstract

Phytoremediation of metalloids by conifers is not widely studied although they may be relevant for several contaminated sites, especially those located in cold areas and sometimes under dry climates. Here, seeds of Douglas fir were sown in greenhouse on three soils collected in two French former mines: a gold mine (soils L1 and L2) and a lead and silver mine (soil P). These soils are highly contaminated by Pb, As, and Sb at different concentrations. Plants were harvested after ten weeks. Growth parameters, primary metabolite content, and shoot and root ionomes were determined. Douglas firs grown on the soils L1 and P had a lower biomass than controls and a higher oxidation status whereas those grown on the soil L2 exhibited a more developed root system and only slight modifications of carbon and nitrogen nutrition. Based on trace element (TE) concentrations in shoots and roots and their translocation factor (TF), Douglas fir could be a relevant candidate for As phytoextraction (0.8 g. kg(-1) dry weight in shoots and a TF of 1.1) and may be used to phytostabilize Pb and Sb (8.8 g and 127 mg. kg(-1) in roots for Pb and Sb, respectively, and TF lower than 0.1).

Effect of fertilization of a biochar and compost amended technosol: Consequence on Ailanthus altissima growth and As‐ and Pb‐specific root sorption

“…Roots can act as a physical barrier against aerial translocation of metal(loid)s through their Casparian strip, in order to restrict metal(loid)s in the roots and prevent their translocation, which indirectly protects the photosynthetic machinery from the toxic effects of As. Finally, the different washing treatments allowed to assess the quantity of metal(loid)s that is adsorbed on the root surface compared to the fraction that is really incorporated inside the root tissues (Bonet et al, 2016;Chaignon & Hinsinger, 2003). These washing treatments showed that As was proportionally more absorbed inside the roots compared to Pb that was mainly adsorbed on the root surface, probably on the cell wall, which could be a tolerance mechanism towards Pb (Macfie & Welbourn, 2000).…”

“…Finally, the different washing treatments allowed to assess the quantity of metal(loid)s that is adsorbed on the root surface compared to the fraction that is really incorporated inside the root tissues (Bonet et al., 2016; Chaignon & Hinsinger, 2003). These washing treatments showed that As was proportionally more absorbed inside the roots compared to Pb that was mainly adsorbed on the root surface, probably on the cell wall, which could be a tolerance mechanism towards Pb (Macfie & Welbourn, 2000).…”

“…For each plant, the root system was divided in two: the first half was washed with tap water and distilled water, whereas the other half was washed with either CaCl 2 (0.05 M), EDTA (20 mM, 20 min), or HCl (0.01 M) before the distilled water washing. Such treatments removed the proportion of metal(loid)s adsorbed on the root surface (Bonet et al., 2016; Chaignon & Hinsinger, 2003; Macfie & Welbourn, 2000). Following all these treatments, plant organs were dried for 72 hr at 60°C, and their dry weights were determined.…”

Efficiency of metal(loid) phytostabilization by white lupin (Lupinus albus), common vetch (Vicia sativa), and buckwheat (Fagopyrum esculentum).

“…We collected the rst 15-20 cm of soil on two French contaminated sites. The rst site is close to a former mine of lead and silver located at Pontgibaud in the Puy-de-Dôme (Pascaud et al, 2014;Bonet et al 2016;Hbaieb et al 2018). The second site is close to a former mine of tin and tungsten at Vaulry in Haute-Vienne.…”

“…The content of total free amino acid (TFAA), total free proline, total non-protein thiols (NPT) and thiobarbituric acid reactive substances (TBARS) was calculated after growing frozen organs with 10% (w/v) trichloroacetic acid containing 6.3 mM diethylenetriaminepentaacetic acid (Bonet et al 2016). TFAA and proline were quanti ed after incubation at 95°C with two different reagents containing ninhydrin.…”