XVI International Botanical Congess
Proton fluxes in rhizosphere were quantified through image analysis of root embedded agar gel containing pH indicator and different concentrations of KNO3. Under dark, proton influx (alkalization) was observed all along the root axis, which was increased with the increase of KNO3 in the gel. In contrast, under light on shoot, a localized proton efflux (acidification) was observed at middle portion of the root axis. The efflux was greatest with no nutrient in gel. This efflux enhanced with increase of light intensity and leaf area, but restricted with use of proton pump inhibitors on roots. These results suggest that the localized proton efflux was independent from ion uptake but dependent on light on shoot, and it could be resulted from local activation of proton pump in the root by photosynthesis.