Ecotoxicological effects of cadmium on three ornamental plants

Ecotoxicological effects of cadmium (Cd) on three ornamental plants African marigold (Tagetes erecta), scarlet sage (Salvia splendens) and sweet hibiscus (Abelmoschus manihot) were investigated. Seeds of these plants were exposed to five different concentrations of Cd (0-50 mgl(-1)). Ecotoxicological indexes based on inhibition rate (IC) of seed germination, root and shoot elongation, biomass (fresh weight and dry weight), as well as IC50 (Cd concentration when 50% plants show inhibition) and tolerance indexes (the ratio of maximum root length in an experimental group to that in a control group) were determined. The results indicated that Cd had little effects (p>0.05) on seed germination of the three plants and shoot elongation of scarlet sage (S. splendens). Cadmium had significant (p<0.05) inhibitory effects on root elongation of the three plants and shoot elongation of African marigold (T. erecta). The fresh weight biomass of scarlet sage (S. splendens) was most sensitive to Cd, while that of sweet hibiscus (A. manihot) was least sensitive. On a dry weight basis, African marigold (T. erecta) was the least sensitive, and scarlet sage (S. splendens) was the most sensitive to Cd. Based on IC50 of seed germination, sweet hibiscus (A. manihot) was the most insensitive plant with an IC50 value as high as 428.0 gl(-1). According to Cd-tolerance indexes under the same Cd concentration, sweet hibiscus (A. manihot) was the most tolerant plant whereas scarlet sage (S. splendens) was the most sensitive one.