The development of the relaying competence in Dictyostelium discoideum

The fraction, X2, of a population of D. discoideum cells competent to relay an aggregative signal has been measured as a function of time, t, spent in interphase. X2(t) is less than 0.I up to 5 h, increases slowly to 0.4 by 8 h 20 min, and saturates at I by 10 h. The hypothesis that cellular interactions might enhance X2(t) was tested by mixing populations of cells set into interphase at different times. No interactions were found. External stimulation did not affect X2(t).