Microcystin uptake inhibits growth and protein phosphatase activity in mustard (Sinapis alba L.) seedlings.

Mustard (Sinapis alba L.) seeds were cultivated for seven days on a solid nutrient medium supplemented with 040 microg microcystin-RR per ml. Microcystin-RR affected seedling growth (IC50 0.8 microg/ml) and microcystin concentrations > or =5.0 microg/ml produced malformed plants. The inhibition of protein phosphatase 1 and 2A activity correlated with the growth inhibition. The seedlings were also shown to take up 3H-dihydromicrocystin-LR derived radioactivity up to a level corresponding to ca. 80 ng toxin per mg plant protein.