Toxic effect of heavy metal terbium ion on cell membrane in horseradish

In order to understand the toxic mechanism of terbium ion (Tb(III)) on plants, the subcellular distribution of Tb(III) in horseradish, the effect of Tb(III) on the composition of the fatty acids in the cell membrane, the peroxidation of membrane lipid, the morphological character of protoplast, the cellular ultrastructure in horseradish were investigated using transmission electron microscopic autoradiography, molecular dynamics simulation, gas chromatography, scanning electron microscopy and transmission electron microscopy. The results show that Tb(III) could not enter the horseradish cell in the presence of 5 mg L−1 Tb(III) and it was distributed on the cell wall and plasma membrane. The behavior caused the decrease in the contents of unsaturated fatty acids and then the increase in the peroxidation of membrane lipid. Thereby the structure of horseradish cell was damaged. The effects of Tb(III) mentioned above were aggravated in horseradish treated with 60 mg L−1 Tb(III) because Tb(III) could enter the horseradish cell. It was a possible cytotoxic mechanism of Tb(III) on horseradish.