Copper uptake, localisation and biochemical and physiological traits were studied in hydroponically-grown Erica andevalensis plants at different increasing concentrations of Cu (1 μM, 50 μM, 100 μM, 250 μM, and 500 μM). Increasing Cu concentration in the nutrient medium led to a significative reduction in plant growth rate, an increase in root Cu concentration, leaf photosynthetic pigments and root peroxidase activity. Copper accumulation followed the pattern roots>stems>leaves, a typical behaviour of metal-excluders. Copper treatments led to significant changes in the free amino acid composition in shoots and roots and the concentration of polyamines in shoots. Analysis by scanning electron microscopy coupled with elemental X-ray analysis (SEM–EDX) showed a partial restriction of upward Cu transport by root vascular tissues. In leaf tissues, Cu mostly accumulated in the abaxial epidermis, suggesting a mechanism of compartmentalization to restrict mesophyll accumulation. The toxic effects of excess Cu were avoided to a certain extent by root immobilization, tissue compartmentalization, synthesis of complexing amino acids and induction of enzymes to prevent oxidative damage are among mechanisms adopted by Erica andevalensis to thrive in acidic-metalliferous soils.

This research was supported by Spanish Ministry of Science and Education (MEC) (CGL2006-1418 and José Castillejo Program) and Ramón Areces Foundation. The authors thank Manlio Colella and Sergio Sorbo from CISME (Naples, Italy), for their technical assistance in SEM–EDX analysis and the techniques from the Greenhouse of Seville University for their technical assistance in plant cultivation.

Peer reviewed