Tolerance to high Zn in the metallophyte Erica andevalensis Cabezudo & Rivera

The tolerance to high Zn was studied in the metallophyte Erica andevalensis Cabezudo & Rivera grown in nutrient solutions at different Zn concentrations (5, 500, 1,000, 1,500 and 2,000 μM Zn). Plant growth and nutrient uptake were determined. Metabolic changes were assessed by the analysis of peroxidase activity, organic metabolites related to metal chelation (amino acids, organic acids (malate, citrate) or protection (polyamines). While plants tolerated up to 1,500 μM Zn, despite presenting of low growth rates, the concentration of 2,000 μM Zn was toxic producing high mortality rates. Roots accumulated high Zn concentration (11,971 mg/kg) at 1,500 μM external Zn) apparently avoiding metal transfer into shoots. After 30 days of treatment with high Zn (1,000 and 1,500 μM Zn), the leaves accumulated high levels of glutamine. Short-term treatment with 500 μM Zn, significantly increased the concentration of asparagine and glutamine in roots. Citrate concentration was also considerably increased when exposing roots to Zn excess. Metal immobilization in the root system, low interference with the uptake of nutrients and an increased production of putative organic ligands (amino acids, citrate) might have provided the Zn tolerance displayed by Erica andevalensis.