Influence of Irradiance on H⁺ Efflux and Cl^- Influx in Chara corallina: An Investigation Aimed at Testing Two Cl^- Transport Models

Abstract

Parallel studies on the influence of irradiance on net H+ efflux and *36Cl- uptake were conducted on C. corallina. Following the dark-to-light transition, a lag period of 8-15 min was observed before net H+ efflux activity could be discerned experimentally. Decreasing the irradiance did not significantly lengthen this lag period. Studies on *36Cl- uptake revealed that a lag period of 40-60 min was required before the Cl- transport system attained maximum activity, governed by the prevailing experimental conditions. These results are discussed in relation to the Cl- transport hypotheses proposed by Spear et al. and by Smith. It would seem that the hypothesis of Spear et al., in its present form, is invalid for Chara corallina. The results were inconclusive in terms of support (or otherwise) for a Cl-/OH- antiporter. However, the Cl-/OH- antiporter hypothesis originally proposed by Smith will require significant modification, especially in terms of the energy supply.