Microautoradiographic investigations of sulfate uptake by glands and epidermal cells of water lily (Nymphaea) leaves with special reference to the effect of poly-l-lysine

Summary

The uptake of³⁵S-labelled sulfate ions into hydropote cells (densely cytoplasmic gland cells) and into epidermal cells (highly vacuolated cells) ofNymphaea leaves is dependent on metabolic energy. Only a very small fraction of the accumulated³⁵S is incorporated into organic macromolecules during the experimental period. Both cell types exhibit a hyperbolic isotherm for³⁵S uptake from labelled K₂SO₄ solutions over an external concentration range of 0 to 0.5mm. Although the gland and epidermal cells behave qualitatively similarly, the glands generally absorb about twice as much³⁵S per unit area of sections of the cells as do the epidermal cells. At 3 °C, poly-l-lysine concentrations of 10⁻⁸ m and up to 10⁻⁷ m enhance³⁵S uptake by the epidermal and gland cells for the first 7.5 hr after application of the poly-l-lysine. Samples treated with 5×10⁻⁷ m poly-l-lysine are indistinguishable from the controls over the same period. After longer periods of treatment with poly-l-lysine (7.5 to 24 hr), the rates of³⁵S uptake were reduced by all poly-l-lysine concentrations between the range 10⁻⁸ to 5×10⁻⁷ m. After 7.5 hr of³⁵S uptake, the control samples contained the smallest amount of label, but after an uptake period of 24 hr the amount of label in the controls is considerably larger than in samples treated with poly-l-lysine. The results suggest that poly-l-lysine increases the membrane permeability and alters the metabolic uptake of sulfate in both hydropotes and epidermal cells.