Fig. 4. Effects of nutritional shifts on pH_i. Phluorin-expressing wild-type cells were grown to early logarithmic phase in EMM(glutamine) pH 5.5 (left) or EMM(proline) pH 5.5 (right) and mounted in the same media in the flow chamber. After a 30-60 minute equilibration time the perfusion medium was switched (t=0) to EMM(proline) pH 5.5 (left) or EMM(glutamine) pH 5.5 (right). The top panels show the mean internal pH of 20-40 cells plotted as a function of time. Error bars indicate s.d. Lower panels are scatter plots of internal pH as a function of cell length at the indicated times. Open diamonds indicate binucleate cells whereas closed diamonds indicate uni-nucleates.