Investigations into the inhibitory effects of microcystins on plant growth, and the toxicity of plant tissues following exposure

The cyanobacterial toxins microcystins are known to affect a number of proc esses in plant tissues, and their presence in water used for irrigation may have considerable impact on the growth and development of crop plants. In this study, two plant bioassays were employed to investigate the phytotoxic effects of microcystins. A plant tissue culture assay revealed that the gr owth and chlorophyll content of Solanum tnberosum L. cultures was inhibited at microcystin-LR concentrations of 0.005 and 0.05 mug cm(-3), respectivel y. A previously developed bioassay was also employed to determine the effec ts of three commonly occurring microcystin variants on the growth of Synapi s alba L. seedlings. Microcystins-LR, -RR, and -LF inhibited the growth of seedlings, with GI(50) values of 1.9, 1.6 and 7.7 mug ml(-1), respectively. The growth of Phaseolus vulgaris was also examined in the presence of micr ocystin-LR. The toxin was found to have little effect on growth for up to 1 8 days, but impaired the development of the roots of exposed plants, causin g them to take up approximately 30% less growth medium than those grown in the absence of toxin. Microcystin was also detected in the tissues of expos ed plants using a commercially available ELISA kit, suggesting that the upt ake of these toxins by edible plants may have significant implications for human health. (C) 2001 Elsevier Science Ltd. All rights reserved.