Sulfate Uptake and Its Regulation in Lemna paucicostata Hegelm. 6746

Abstract

The results of studies of SO₄²⁻ uptake by Lemna paucicostata are most simply interpreted by the hypothesis that at least two components are involved, one saturating and one linear, `nonsaturating.' The saturating component has a low K_m and high specificity for SO₄²⁻. Uptake by the nonsaturating component is less affected by pH and temperature than is that of the saturating system. SO₄²⁻ efflux is not quantitatively important in Lemna under standard conditions (20 micromolar SO₄²⁻) (Datko AH, SH Mudd 1980 Plant Physiol 65: 906-912). 55% of newly taken up ³⁵SO₄²⁻ enters a slowly turning over compartment (vacuole?); 45% remains in a compartment (cytoplasm?) in which it is rapidly metabolized to organic compounds.