Effect of combined pollution of chromium and benzo(a)pyrene on seed growth of Lolium perenne.

The single and joint effects of chromium (Cr) and benzo (a) pyrene (B (a) P) on the seed germination and the elongation of root and shoot of Lolium perenne were investigated. Seed germination represents the first important step to effective phytoremediation. Young seedlings may be susceptible to PAH and heavy metal contaminants. The results showed that in solution, increasing concentration of Cr could inhibit the germination rate as well as root and shoot elongation of L. perenne. Also, the increasing concentration of B (a) P (1-4 mg L(-1)) could accelerate the germination rate. The joint toxicity of Cr and B (a) P showed that increasing concentration of Cr and B (a) P had significant antagonistic effect on the germination rate of L. perenne. In the single factor experiments and joint effect tests of Cr and B (a) P on the seedling growth, the root and shoot elongation were inhibited significantly (p<0.05) for higher concentration of Cr whereas increasing concentration of B (a) P accelerated the shoot elongation. There were significant relationships between the concentration of pollutants and root and shoot elongation (p<0.05). Higher concentration of B (a) P with low concentration of Cr had significant antagonistic effect on shoot and root elongation of L. perenne in solution tests. Also, low concentration of B (a) P with increasing concentration of Cr had a significant synergistic effect on shoot elongation. The toxicity effects of Cr and B (a) P to seed germination, root and shoot elongation are-root elongation>shoot elongation>germination rate.