In root-hair cells of Sinapis alba, cytosolic pH, cytosolic [Cl-], membrane potential, and membrane resistance have been measured to investigate proton-driven Cl- transport across the plasma membrane. Rapid lowering of the external pH transiently increased cytosolic [Cl-] and acidified the cytoplasm. To an abrupt increase in external [Cl-] the cells reacted with a rapid initial depolarization and a subsequent slower hyperpolarization, which was accompanied by an increase in cytosolic [Cl-] and [H+]. These results are indicative of an nH+/Cl- symport with n > 1. Simultaneous recording of the membrane potential, the proton motive force, cytosolic pH, and cytosolic [Cl-] reveals that kinetically this Cl- transport depends on the pH gradient across the plasma membrane rather than on the membrane potential.
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H. H. Felle (1994) studied this question.