Compartmentation of PO4 - Uptake and 32P Efflux in the Rhizoid Cells of Chara hispida L.

Abstract

The uptake of 32 P-orthophosphate by the rhizoid of Chara hispida has been measured by disappearance from the medium. The time course of the loss of 32 P associated radioactivity of previously “loaded” rhizoid cells was also studied. The time courses in the two experimental series are similar, and yield in both cases. three different components which have corresponding half-times for the exchange of the isotope 31 P with 32 P. In the uptake study these are 1–3 min, 28 ± 3 min and 378 ± 52 min (n = 3); for the efflux they are 2.2 ± 0.35 min 8.1 ± 0.4 min and 374 ± 77 min (n = 5). The results are consistent with a three-compartment system representing the water free space, the cytoplasm and the vacuole.