ACCLIMATION OF TREES TO POLLUTION STRESS - CELLULAR METAL TOLERANCE TRAITS

Cell suspension cultures were established from shoot expiants of mature trees of Acer pseudoplatanus L. (sycamore) at a site contaminated by aerial deposition of copper and cadmium from metal processing industry, and from the same species at uncontaminated sites. The responses of cell cultures to elevated metal concentrations in growth media differed markedly according to site of origin. Both Cu and Cd, applied singly at concentrations of 10-15 mg 1-1, inhibited growth and were toxic to cultures originating from the uncontaminated sites, but not to cultures from the contaminated site. This metal tolerance trait in the cultures from the contaminated site was stable through repeated sub-culturing. It could also be induced in one culture originating from the reference uncontaminated site, by gradually exposing the culture to increasing concentrations of Cu. A reduced level of metal removal from the media was found in tolerant cultures, compared to non-tolerant cultures. The results of these experiments demonstrate the occurrence of an alteration of gene expression in response to pollution stress, suggesting that metal tolerance may be induced within shoot meristems in vivo. It also represents the first example of non-mycorrhizal adaptation to metal toxicity identified in woody plants. © 1992 Annals of Botany Company.