Use of a pH indicator in protoplast culture medium

Abstract A pH indicator dye, bromocresol purple, has been added to Petunia inflata protoplast culture medium and found to have no detectable effect on protoplast colony-forming efficiency or [ 3 H]thymidine incorporation. A second pH indicator, BDH 4460, was found to be inhibitory. The colour of bromocresol purple in solution is very sensitive to pH in the region 5.5–6.0. Routine use of this indicator, which is stable to autoclaving, considerably simplifies aseptic pH adjustment of unbuffered liquid or viscous media as well as signifying metabolic activity of the cultured protoplasts.