CHARACTERISTICS OF ALUMINUM-PHOSPHATE-ADAPTED CARROT CELLS - UPTAKE AND UTILIZATION OF THE PHOSPHATE

To elucidate the mechanism responsible for the superior growth of a se lected line of carrot cells (Daucus carota L. cv MS Yonsun) in medium that contained AlPO4, kinetic studies of the uptake of phosphate and t he efficiency of utilization of phosphate were performed with the sele cted cells and the wild-type cells. When the two cell lines were grown in a medium with adequate soluble phosphate (2 mM), there was no diff erence between their growth rates. Rates of increase in fresh weight a s a function of increasing concentration of phosphate in the medium we re also identical between the cell lines, indicating that the efficien cy of utilization of phosphate by the selected cell line was similar t o that by the wild-type cells. However, rate of uptake of phosphate by the selected cells under phosphate limited conditions (20-mu-M NaH2PO 4 at pH 5.6) was about 5-fold higher than that by the wild-type cells. Apparent K(m) values for the uptake of phosphate were calculated to b e 13.6 and 9.1-mu-M for the selected and the wild-type cells, respecti vely. The V(max) value was estimated to be 88.8 nmol per g fresh weigh t per min for the selected cells and 28.2 for the wild-type cells. Thu s, the selected cells has an enhanced system for uptake of phosphate w hereby there was an increase in the rate of the uptake without any dra matic change in the affinity for phosphate ions.