The Effect of the Hydrogen Ion and Light on the Membrane Properties of Nitella

Abstract

Using the Kitasato hypothesis as a basis, the effect of H+and light on Nitella was investigated. Upon a light to dark transition, the cell resting potential at pH 5.7 depolarized, whereas at pH 4.7 the membrane became hyperpolarized. Membrane conductance and H+ extrusion were not significantly affected by the pH change 5.7 to 4.7. Light promoted increases in both membrane conductance and H+ fluxes. All cells except those having extreme resting potential values, either high or low, were responsive to light. The action spectra for H+ flux, resting potential and membrane conductance is not the same as that for photosynthesis suggesting the possibility of another more complex mechanism(s) being involved with the light effects on Nitella.