Utilization of anhydrous aluminum phosphate as a sole source of phosphorous by a selected carrot cell line

Two variants of carrot (Daucus carota L. cv. MS Yonsun) cell lines, which had been selected with Al-phosphate as a sole source of phosphorous, were characterized on their mechanisms of phosphate-utilization from Al-phosphate. Both cell lines excreted citrate into the medium. The amount of citrate excretion was highly correlated with cell growth in the presence of Al-phosphate. There was about a 1 to 1 correlation between solublized-Al and excreted-citrate in the medium during cell growth. These results suggest that 1) the citrate could chelate with Al, at a 1 to 1 ratio, in Al-phosphate, 2) the citrate-chelated Al remains outside the cells, and 3) solublized phosphate from Al-phosphate is utilized for the growth of carrot cells. The characteristics of the selected cells were very stable, since the rate of citrate-excretion showed no change after subculturing 25 passages without Al-phosphate.