Effect of pH on the Membrane Potential and Electrical Resistance of Nitella flexilis in the Presence of Calcium

• Published in: Journal of Experimental Botany
• Main Authors: LEFEBVRE, J., GILLET, C.
• Format: Text
• Language: English
• Published: Oxford University Press 1973
• Subjects: Articles; Nitella flexilis
• Online Access: http://jxb.oxfordjournals.org/cgi/content/short/24/6/1024; https://doi.org/10.1093/jxb/24.6.1024

Effects of pH on the membrane potential and electrical resistance of Nitella were investigated in a bathing medium with or without calcium. The membrane potential became more negative as the external pH was raised, at a faster rate in the presence of calcium than in its absence. The value then achieved by the potential could be reversed by restoring the original pH whilst in a Ca-free medium the cell remained ‘hyperpolarized’. Tenfold changes of the external concentration of potassium brought about larger modifications of the membrane potential when the pH of the solution was high and calcium concentration low. The electrical resistance was lowest in alkaline and calcium-free solutions. We conclude that calcium prevents the mediation of some changes in the membrane structure by lowering the concentration of external H+ ions, and that the permeability of Nitella to potassium increases with rising pH.