Cell death caused by a combination of aluminum and iron in cultured tobacco cells

The inhibition of growth of tobacco cells (Nicotiana tabacum L. cv. Samsun) after treatment with Al in medium containing high concentrations of cations requires the presence of Fe (II or III) during the treatment. We examined whether the inhibition of the post-treatment growth is due to cell death occurring during the treatment with Al and Fe. In cells at the end of Al treatment, the integrity of the plasma membrane and the integrity of the mitochondrial inner membrane were monitored by use of Evans blue staining and the cleavage of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), respectively. Time-course and dose-response experiments indicate that the inhibition of post-treatment growth is strongly related to Evans blue uptake, but not to MTT cleavage. These results suggest that the loss of integrity of the plasma membrane caused by a combination of Al and Fe directly contributes to cell death and the inhibition of post-treatment growth.