Characterization of two tobacco cell lines selected to grow in the presence of either ionic Al or insoluble Al-phosphate

A tobacco cell line tolerant to ionic A1 (AIT) was selected at a frequency of 10^-6to 10^-7by plating the wild-type cells on agar medium containing 2.5 mm AICI₃and 0.1 mM phosphate at pH 4.0. Another cell line which is able to grow with insoluble Al-phosphate as a sole source of phosphate (IPU) was also selected by subculturing the wild-type cells for more than 10 passages in suspension culture in the presence of 2 mM phosphate and 4 mM A1C1₃at pH 5.0. The IPU cell line also tolerated ionic A1 but the AIT line showed poor growth with insoluble Al-phosphate as a sole source of phosphate. Both cell lines excreted citrate into the media. The rate of citrate excretion by the IPU cell line, on a fresh weight basis, was higher than that by the AIT and wild-type cell lines.