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 mu M) 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 mu M Cd. All genotypes showed high tolerance to low Cd levels (5 mu M and 25 mu M Cd), in contrast to high Cd levels (i.e. 50 mu M and 100 mu M) that severely disturbed plant growth of all genotypes. Cadmium concentrations reached 165.0-1251.0 mu gg(-1) DW in leaves, 22.9-331.2 mu gg(-1) in stems among the genotypes at 5-25 mu M Cd, and Cd mainly accumulated in the roots. Although willow tissues can accumulate relatively high Cd concentrations under high Cd levels (50 mu M), they are not suitable for phytoextraction of Cd due to poor growth.