Metal resistance in red maple (Acer rubrum) callus cultures from mine and smelter sites in Canada

The response of red maple (Acer rubrum L.) to elevated heavy metal concentrations in surface soil, arising from either atmospheric deposition or mining activities, was investigated using callus tissue studies. Callus cell lines were established from shoot tips of mature red maple growing at sites in rural and industrial locations in Ontario and Quebec differing in metal contamination. At Sudbury and Rouyn-Noranda, the trees were stunted and were established before smelting operations began. Surface soil in the rooting zone of many of the trees in the industrial areas was heavily contaminated with metals, and large differences in soil metal concentration at the bases of different trees were found. A significant positive linear relationship between Ni resistance, measured as an increase in fresh weight of callus on Ni- amended media, and total extractable Ni in soil at the base of trees was identified. Resistance to Ag and Co was also significantly greater in cell lines established from trees growing in soils containing highly elevated concentrations of these metals. It appears that red maple is able to produce an adaptive response to metal exposure which is identified in cells derived from shoot tips. This metal-specific, adaptive response may be particularly crucial for the survival of trees to rapid environmental changes. [ABSTRACT FROM AUTHOR]