Profiles of Chloride Concentration and PD in the Root ofCommelina communisL.

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Abstract
Chloride concentrations in longitudinal files of cells across the root of Commelina communis have been determined. Vacuolar sap was taken from the root using a microsampling technique and chloride concentration determined on nanolitre samples by electrometric microtitration. No radial gradient in vacuolar chloride was observed, either for roots grown in a nutrient solution containing a low level, or for those grown in a solution containing a high level, of chloride. Vacuolar electrical potentials were also determined, on attached and excised roots. The PD was found not to vary significantly across the root from epidermis to pericycle despite the PD in attached roots being 50 mV more negative than that in excised roots. These results are discussed in relation to the mechanism of ion transport across the root.