Cadmium Accumulation and Tolerance in Seven Ornamental Willow Genotypes

Cadmium (Cd) accumulation and tolerance in seven ornamental willow genotypes were investigated at different Cd levels (0, 5, 25, 50, and 100 µM) through hydroponic culture in a greenhouse. Severe phytotoxic symptoms in leaves and roots including leaf chlorosis and root browning were noticed when grown at ≥ 50 µM Cd. All genotypes showed high tolerance to low Cd levels (5 µM and 25 µM Cd), in contrast to high Cd levels (i.e. 50 µM and 100 µM) that severely disturbed plant growth of all genotypes. Cadmium concentrations reached 165.0-1251.0 µg g^-1 DW in leaves, 22.9-331.2 µg g^-1 in stems among the genotypes at 5-25 µM Cd, and Cd mainly accumulated in the roots. Although willow tissues can accumulate relatively high Cd concentrations under high Cd levels (≥ 50 µM), they are not suitable for phytoextraction of Cd due to poor growth.