Translocation: Efflux of sugars across the plasmalemma of mesophyll protoplasts [of wheat and tobacco]

During photosynthesis by mesophyll protoplasts of wheat and tobacco, a linear efflux of sucrose and hexoses to the medium was observed, with the size of the intraprotoplast sugar pools remaining constant. Efflux of metabolites labeled by 14CO2 fixation was initially low because of dilution by internal pools, but increased exponentially with time. The results have significance both in terms of the mechanism of translocation and the use of isolated protoplasts in photosynthetic studies.