Potassium Transport Across the Membranes of Chara: III. EFFECTS OF pH, INHIBITORS AND ILLUMINATION

Smith, J. R., Walker, N. A. and Smith, F. A. 1987. Potassiumtransport across the membranes of Chara. III. Effects of pH,inhibitors and illumination.—J. exp. Bot. 38: 778–787. The effects of several treatments, normally used to inhibitelectrogenic proton transport, upon the potassium permeability(P_k) of the membranes of Chara were examined by means of simultaneousmeasurements of the ⁴²K influx (ⁱⁿ_K) and the membrane electricalconductance (G_m). ⁱⁿ_K, P_K and G_mwere found to be substantiallyunaffected when the external pH (pH?) was varied over the range5?0 to 85. However, when pH? was increased to 11 it was foundthat, although G_m increased considerably, both P_k and ⁱⁿ_K decreasedtypically by an order of magnitude. When cells were placed intotal darkness, P_K decreased substantially only after one dayhad elapsed. For the particular experimental conditions used,the inhibitors DES, NaN₃, and La₃₊ were found to alter P_K, whereasDCCD left P_K substantially unaffected. These results suggestthat care must be taken with some common procedures used toexamine the electrical properties of the electrogenic protonpump. Key words: Potassium, pH, illumination, inhibitors