Effect of Temperature on Punchthrough in Electrical Characteristics of the Plasmalemma of Chara coralinna

Abstract

At the punchthrough, the current required to maintain the hyperpolarized potential difference (p.d.) of the plasmalemma increases very rapidly with increasing hyperpolarization so that, in the steady state, the membrane cannot be hyperpolarized beyond a certain level. It was found that punchthrough in the plasmalemma of C. corallina occurred at more negative (i.e. at greater hyperpolarizing) potentials as the temperature was decreased, from a value of ~ -310mV at T = 32°C to ~ -420 mV at T = 5°C. Some considerations are given to the compressive stress induced in the plasmalemma due to the electric field. These stresses at the p.d. values required for punchthrough are very considerable (~ 3 x 10*6 Nm*-²), and could lead to significant strains in the membrane. The degree of electromechanical compression of the membrane would increase with increasing temperature if, as the evidence cited suggests, the elastic modulus of the membrane decreases with increasing temperature. This would account for the decrease in the absolute value of the p.d. required for punchthrough with increasing temperature.