Viola baoshanensis, a plant that hyperaccumulates cadmium

This paper reports upon the finding of Viola baoshanensis, a cadmium (Cd) hyperaccumulator through field survey and greenhouse experiments. Average Cd concentration in the shoots and roots of V. baoshanensis growing on Baoshan lead/zinc mine in Hunan Province, China, was 1168 and 981 mg/kg, respectively, varying from 456 to 2310 mg/kg in the shoots, and from 233 to 1846 mg/kg in the roots. The ratio of Cd concentration in shoot to root (DW) and that in plant shoots to total concentration in surface soil was 1.32 and 2.38, respectively. Under nutrient solution culture, bio-mass (DW) of V. baoshanensis exposed to 0-30 mg/L Cd in solution increased with Cd supply increasing and reached a maximum at 30 mg/L Cd. Further increase of Cd concentration (40, 50 mg/L) in solution significantly reduced biomass. Cd concentration in the shoots was positively correlated with Cd concentration in the culture medium. Cd concentration in the shoots reached 4825 mg/kg at 50 mg/L Cd solution. The ratio of Cd concentration of shoots to roots in V. baoshanensis was greater than 1 at all Cd treatments, with an average of 1.67 (1.14-2.22). The results indicate that V. baoshanensis is a Cd hyperaccumulator plant.