The use of Lepidium sativum in a plant bioassay system for the detection of microcystin-LR

Toxin-producing cyanobacteria pose a worldwide health threat to humans and animals due to their increasing presence in both drinking and recreational waters. Detection of microcystins in water generally relies on specialised equipment and a delay of several days for transport and analysis. Little work has, however, been done on establishing a simple, cost-effective and sensitive plant bioassay for the detection of microcystin-LR (MCLR) in water at the WHO Tolerable Daily Intake guideline level of 1 mug/l. We investigated the effect of a MCLR extract at 1 and 10 mug/l on the growth of Lepidium sativum over 6 days. Exposure to 10 mug/l MCLR resulted in a significant decrease in root and leaf lengths and fresh weights of seedlings when compared to the controls. These results were consistent with seedlings exposed to pure MCLR at 10 mug/l. Seedlings exposed to 1 mug/l MCLR showed a significant decrease in root development from day 2 to day 6. Glutathione S-transferase and glutathione peroxidase activities were also significantly raised in plants from days 5 and 4, respectively, at both toxin levels investigated. (C) 2003 Elsevier Science Ltd. All rights reserved.