Evidence of sulfur-bound reduced copper in bamboo exposed to high silicon and copper concentrations

Abstract

We examined copper (Cu) absorption, distribution and toxicity and the role of a silicon (Si) supplementation in the bamboo Phyllostachys fastuosa. Bamboos were maintained in hydroponics for 4 months and submitted to two different Cu (1.5 and 100 μm Cu(2+)) and Si (0 and 1.1 mM) concentrations. Cu and Si partitioning and Cu speciation were investigated by chemical analysis, microscopic and spectroscopic techniques. Copper was present as Cu(I) and Cu(II) depending on plant parts. Bamboo mainly coped with high Cu exposure by: (i) high Cu sequestration in the root (ii) Cu(II) binding to amino and carboxyl ligands in roots, and (iii) Cu(I) complexation with both organic and inorganic sulfur ligands in stems and leaves. Silicon supplementation decreased the visible damage induced by high Cu exposure and modified Cu speciation in the leaves where a higher proportion of Cu was present as inorganic Cu(I)S compounds, which may be less toxic.

Chromium immobilization by extraradical mycelium of arbuscular mycorrhiza contributes to plant chromium tolerance

“…elements, Cu and Zn showed different distribution patterns from Ca, K and Fe, which may be caused by their chemical properties. Cu and Zn are micronutrient elements that can be combined with organic acids for translocation through xylem (Terzano et al, 2008;Collin et al, 2014), while Ca and K are macronutrient elements that can be transported in xylem or phloem (White, 2001;Ahmad and Maathuis, 2014). Fe was mainly accumulated in the cortex, which can be explained by the previous study showing that Fe was likely chelated to the nonproteinogenic amino acid nicotianamine (NA) in the epidermal (Curie et al, 2009).…”

Silicon-Mediated Tolerance to Metal Toxicity

“…The leaf phytoliths formed in Si-treated plants might have partly contributed to tolerance by Cu immobilization and inactivation. However, contrasting results have recently been reported by Collin et al ( 2014 ) that Cu concentrations in leaves, stems or roots of bamboo grown with 100 μM Cu in a hydroponics system were not affected by Si, but the proportion of Cu adsorbed on roots was 61.5 % in the Cu plus Si treatment compared to 42 % in the Cu treatment only, suggesting that biologically active Cu was reduced by Si supplementation.…”

“…However, contrasting results have been reported (Shi et al 2005b ;Collin et al 2014 ). For instance, Collin et al ( 2014 ) have recently observed that Si supplementation decreased the visible damage in bamboo grown hydroponically with high Cu exposure (100 μΜ Cu) for 4 months, but Si was not directly involved in Cu speciation in roots, which is contrary to the fi ndings of Wang et al ( 2004 ) who associated Si-ameliorated Al toxicity in rice to the formation of HAS in the roots (Wang et al 2004 ).…”

“…Cu toxicity has been recently reported to be mitigated by the addition of Si in Arabidopsis thaliana Khandekar and Leisner 2011 ), Zinnia elegans (Frantz et al 2011 ), Erica andevalensis (Rossini et al 2011) and rice (Kim et al 2014a ). Collin et al ( 2014 ) reported that bamboo grown hydroponically with 100 mM Cu induced suffered a signifi cant growth inhibition with severe visual toxicity symptoms (i.e. chlorotic leaves and brown root coloration); the addition of 1.1 mM Si signifi cantly resorbed those symptoms.…”

“…For instance, Collin et al ( 2014 ) have recently observed that Si supplementation decreased the visible damage in bamboo grown hydroponically with high Cu exposure (100 μΜ Cu) for 4 months, but Si was not directly involved in Cu speciation in roots, which is contrary to the fi ndings of Wang et al ( 2004 ) who associated Si-ameliorated Al toxicity in rice to the formation of HAS in the roots (Wang et al 2004 ). Collin et al ( 2014 ) also showed that Si increased the proportion of Cu(I) S-ligands (organic and inorganic) in leaves of bamboo exposed to high Cu stress and may have enhanced the capacity of the plant to produce S ligand available to bind Cu, thereby increasing the Cu sequestration in a less toxic form. In an earlier report, Shi et al ( 2005b ) showed that most of the total root Cd (87 %) was localized in the symplast of rice grown hydroponically with Cd, whereas the apoplast Cd fraction accounted for only 13 % of the total Cd irrespective of Si treatment.…”