FIG. 3.

A P-stressed P. minimum culture was divided, and one-half was refed with inorganic P. The number of cells increased and the level of ELF-97 alkaline phosphatase activity decreased over time, reaching 0% after about 6 days in the culture to which P had been added. The level of ELF-97 labeling in the half of the culture which was not refed was consistently near 100%. The ELF-97 activity of refed (+P) cultures (solid bars), the ELF-97 activity of −P cultures (shaded bars), the +P cell number (▵), and the −P cell number (○) are shown.