Physiological and biochemical studies on heavy metal tolerance in Festuca rubra cv. merlin

A multi-metal tolerant grass species, Festuca rubru cv. Merlin, was employed to study the mechanism of heavy metal tolerance in higher plants. Physiological studies showed that Merlin cultivar is highly tolerant to copper up to 20.0 mg l-1, in addition to its tolerance to zinc, lead and cadmium. The uptake studies demonstrated that roots may play a key role in copper resistance by accumulating most of copper (about 50 times higher than shoots) and copper uptake restriction in roots may be one of the mechanisms of copper resistance in Merlin. Biochemical studies showed that most of copper (about 90%) in the cytoplasm of roots was associated with a low molecular weight fraction (4,900 daltons), which was induced by the treatment of excess copper. A copper-binding complex (Cu-BP l) with high copper binding capacity (5.17 μmol mg-1) was purified to homogeneity through DE-52 anion exchange chromatography, FPLC Sephadex G-50 gel filtration and reverse-phase HPLC Cl8 chromatography. Amino acid analysis showed that CU-BP l consisted of only four type amino acids, e.g. His (30.9%), Ala (15.1%), Cys (6.5%) and Phe (47.5%). This result clearly indicated that Co-BP l was a novel metal-binding peptide found in plants distinct from conventional metal-binding peptides, e.g. metallothioneins and phytochelatins, which have high content of Cys (about 30%)