Toxicity of copper to Quercus robur (English Oak) seedlings from a copper-rich soil

Wisniewski, L. and Dickinson, N.M. Toxicity of copper to Quercus robur (English Oak) seedlings. ––Acorns were germinated after collection from a mature Q. robur woodland at an historic copper mine site in Cheshire, England, and from an uncontaminated reference site. Hydroponic screening trials of seedlings using 0.5 mg Cu l −1 in 25% Hoagland's solution found no growth differences between sites of origin that indicated tolerance. Copper accumulated in the roots, with restricted transport to foliage. Prolonged exposure caused gross perturbations of root morphology, reduced root and shoot growth, and leaf chlorosis. Pre-exposure of seedlings to low levels of copper and repeated exposure provided little evidence for acclimation to the metal. Damage to photosynthetic systems was reflected in altered chlorophyll ratios and carotenoid pigments, including those related to the xanthophyll cycle. Zeaxanthin biosynthesis was not a particularly sensitive or reliable indicator of plant stress. It is concluded that survival of oak seedlings in the field is related to soil or rhizosphere processes mediating copper mobility, rather than to physiological tolerance or plant acclimation.