Contribution of apoplast to short-term copper uptake by wheat and mung bean roots

In this study we addressed the controversial issue of contribution of cell walls (CWs) to Cu binding in plant roots. We compared short-term Cu uptake at different solution Cu levels by mung bean (Vigna radiata (L.) R. Wilczek) and wheat (Triticum aestivum L., cv. Inna) and by root CWs isolated from either Cu-treated or non-treated plants. Twenty four hours of plant exposure to Cu affected Cu-binding capacity of mung bean root CWs but not wheat CWs. Amounts of Cu associated with CWs and roots increased with Cu concentration. The Cu accumulated in CWs could account for total Cu content of roots (except for wheat in highest Cu treatment). Pectin content of the CWs and their Cu-sorption capacity were positively correlated. The accumulation of Cu in root CWs is a principal response of wheat and mung bean plants to excess Cu, limiting symplastic Cu uptake in roots in short-term treatment. The contribution of CWs to Cu absorption by plant roots depends on Cu level in the medium and plant species.