Measurement of intracellular pH and aspects of its control in higher plant cells cultivated in liquid medium.

The 5,5-dimethyloxazolidine-2,4-dione (DMO) method for the determination of intracellular pH has been adapted to Acer pseudoplatanus cells cultivated in liquid medium. DMO is metabolized by these cells and this parameter has to be taken into account in the measurement of the intracellular concentration of free DMO. As the cells contain a large acidic vacuolar compartment, the intracellular pH estimated from the DMO technique is an overall pHi', the dependence of which on various cytoplasmic and vacuolar characteristics has been discussed. Important modifications of these overall pHi values under the influence of CO2 or NH4+ have been measured. These pHi modifications strongly affect the regulation of cell division through the control of the intracellular concentration of hormones of the auxin type.