Microelectrodes suitable for use in cells with high hydrostatic pressure

Microelectrodes with a 1- to 2-mum tip diameter have been made which are capable of withstanding plant cell hydrostatic pressure on impalement. Filling the electrodes with 1% agar or 5% gelatin in 2 m KCl prevents cytoplasmic contents from moving into the electrode tip on impalement and therefore prevents the irreversible increase in resistance which often occurs. The agar and gelatin electrodes were tested in two fresh water algae, Nitella translucens and Mougeotia sp., and the potentials recorded were found comparable to those recorded with standard 2 m KCl electrodes.