Passive anion transport through the chloroplast inner envelope membrane measured by osmotic swelling of intact chloroplasts

It has been shown that chloride channels are located in the envelope membra nes of chloroplasts [5,11]. In this report, we use the light-scattering tec hnique to measure quantitatively the rate of anion transport through the in ner envelope membrane of isolated intact chloroplasts. Our results permit t o assign the anion transport to the inner envelope of chloroplasts. The ani onic selectivity determined from the kinetics of light scattering indicates that the chloride pathway is also highly permeable for NO2- and NO3-. The sulfate and phosphate anions are impermeant. The chloride flux is not inhib ited by DIDS or NEM and is temperature-dependent. The activation energy of the transport process suggests that the Cl- flux occurs through a channel. (C) 1999 Elsevier Science B.V. All rights reserved.