Earthworm mucus enhanced cadmium accumulation of tomato seedlings

A hydroponic experiment was carried out to study the effects of earthworm (Metaphire guillemi) mucus on tomato Hezuo 903 (Lycopersicon esculentum) seedlings growth and cadmium (Cd) accumulation. The experiment included three levels of Cd addition rates (0, 5 and 10 mg L(-1)), two levels of earthworm mucus addition (20 and 40 ml per pot) treatments (EML and EMH), and the control (CK). The results showed that compared with the control earthworm mucus addition significantly increased shoot and root dry weights of tomato seedling by 13.8-44.5% and 12.4-33.2%, respectively. In contrast, high earthworm mucus addition (EMH) led to a 4% shoot weights decrease at 10 mg Cd L(-1) compared with CK. Cadmium concentrations and accumulations in both shoot and root of tomato seedlings were significantly increased (p < 0.01) with increasing Cd and earthworm mucus addition levels. Cadmium concentrations and accumulations in root were much higher than those in corresponding shoot. Present study indicated that earthworm mucus could enhance tomato seedlings growth and Cd accumulation. Our work might be not only very useful for understanding how earthworms enhance plant growth and heavy metals accumulation, but also for further application of earthworms in phytoextraction.