Glutathione depletion in healthy cadmium-exposed Erica andevalensis

The effects of cadmium (0.05-50 ppm in soils) on the antioxidant mechanisms of Erica andevalensis have been investigated under laboratory-controlled conditions. E. andevalensis, an endemic metal-tolerant species from SW Iberian Peninsula, is able to colonize extreme mine environments and to survive in very acid and metal enriched soils. Cadmium was taken up and accumulated in the leaves up to 0.5 ppm in plants watered with the highest concentration of this metal. the plants exposed to cadmium showed an increase in the levels of ascorbic acid and a decrease in glutathione content. the activities of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) were enhanced whereas those of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were depleted in cadmium treated plants. Despite the fact that cadmium reached the leaves of the plant, and microscopy analysis revealed that it mainly accumulated in the photosyntetic tissue, no significant changes were observed in the chlorophyll conctents. Moreover, no damages were observed, neither visually, nor reflected in lipid peroxidation, suggesting the great effectiveness of the mechanisms of this species to cope with metals.