PLANT UPTAKE OF BICARBONATE AS MEASURED WITH THE C-11 ISOTOPE

11C which is cyclotron produced by14N(P, α)11C(half-life 20.1 M) was use as a tracer of bicarbonate to determine its movements from a nutrient solution through roots to stems and leaves of bush bean plants (Phaseolus vulgaris L. var. Improved Tendergreen). The short time involved and the high solution pH minimized the need for use of the Hederson Hasselbach equation for activity correction. Quantities of11C did move into roots, stems and leaves with a sharp decreasing gradient (root/stem=14.5, stems/leaves=11.7) More11C moved into plants with KHCO3 than with NaHCO3. The (NH4)2SO4 enhanced11C uptake and KNO3 than with competition indicated possibility of some uptake of HCO3-. In an experiment with Galenia pubescens (Eckl. and Zeyh.) Druce, the11C was more readily moved to stems and leaves than in bush bean indicating substantial uptake of HCO3-. © 1979 Martinus Nijhoff, The Hague/Kluwer Academic Publishers.