Study of Erica andevalensis adaptation strategies and distribution

Erica andevalensis Cabezudo & Rivera is a vulnerable edapho-endemic species of the Iberian Pyrite Belt, where it grows on acidic soils (pH 2.5-3.5) particularly contaminated with toxic metals. Its main interest, besides its taxonomic position within genus Erica, relies on its potential use for soil reclamation and landscape restoration. An interdisciplinary study has been undertaken in order to evaluate the tolerance strategies of this species to survive and colonize the mining areas of the Pyritic Belt. Major and trace element concentrations were determined in different soil samples and plant parts of Erica andevalensis growing in Riotinto mining area and different experiments under controlled conditions with different Cu, Zn and Pb concentration in a nutrient solution were carried out. In addition, SEM obervations were done to study localization of some toxic metals (Cu and Pb) at tissue levels. Erica andevalensis tolerance might be associated with preferential accumulation of metals in roots which avoids its translocation into aboveground parts and increased synthesis of organic ligands (e.g. histidine in the case of Zn and Cu exccess) and polyamines (in the case of Cu exccess). Microscopic observations showed that at root level, Pb was mainly localized in the epidermal tissues which act as an effective barrier limiting the transport throught the other tissues. At leaf level a mechanism of Cu compartimentation in the abaxial epidermis was observed that restrict its accumulation in the mesophyll. The results of soil analysis showed a wide spatial heterogeneity of element concentrations in the study area, even if the general feature is a low and/or an imbalanced content of several essential elements. This makes difficult to know which are the soil characters which may particularly affect the species geographical distribution.