Microcystin-RR uptake and its effects on the growth of submerged macrophyte Vallisneria natans (lour.) Hara

Microcystins are hepatotoxins produced by many species of several cyanobacterial genera. Their toxic effects on animals and some terrestrial higher plants have been well studied, but their potential effects on the development of aquatic plant seedlings are not well known, and their uptake by aquatic plants is seldom reported. In our research the seeds and seedlings of the submerged macrophyte Vallisneria natans were exposed to different concentrations of microcystin-RR, which was purified with high-performance liquid chromatography (HPLC). The results indicated that microcystin-RR could accumulate differentially in the roots and leaves of V natans seedlings. Toxin accumulation in the roots and leaves was time- and dose-dependent, with higher uptake detected in the roots. Growth and development detection revealed that V natans was relatively insensitive to microcystin-RR at concentrations ranging from 0.0001 to 0.01 mg/L. However, when the toxin concentration was more than 0.01 mg/L, both the fresh weight and the longest leaf length of seedlings were significantly reduced after a 30-day treatment. The root and leaf numbers were significantly decreased when 10 mg/L of toxin was used. These results suggest that microcystin-RR can be taken up by V natans, which subsequently will retard its development. (c) 2005 Wiley Periodicals, Inc.