Light-dependent phosphate uptake of a submersed macrophyte Myriophyllum spicatum L.

The uptake kinetics of phosphate (Pi) by Myriophyllum spicatum was determined from adsorption and absorption under light and dark conditions. Pi uptake was light dependent and showed saturation following the Michaelis–Menten relation (in light: V = 16.91 × [Pi](1.335 + [Pi]), R2 = 0.90, p < 0.001; in the dark: V = 5.13 × [Pi](0.351 + [Pi]), R2 = 0.77, p < 0.001). Around 77% of the loss of Pi in the water column was absorbed into the tissue of M. spicatum, and only 23% was adsorbed on the surface of the plant shoots. Our study shows that M. spicatum shoots have a much higher affinity (in light: 3.9 μmol g−1 dw h−1 μM−1; in the dark: 3.7 μmol g−1 dw h−1 μM−1) and Vmax (maximum uptake rate, shoot light) for Pi uptake than many other aquatic macrophytes (in light: 0.002–0.23 μmol g−1 dw h−1 μM−1; in the dark: 0.002–0.19 μmol g−1 dw h−1 μM−1), which may provide a competitive advantage over other macrophytes across a wide range of Pi concentrations.

Research highlights
► We modeled uptake kinetics of phosphate in Myriophyllum spicatum under light and dark condition.
► Pi uptake was light-dependent and followed the Michaelis–Menten relation.
► Around 77% of the loss Pi in the water column was absorbed, and the rest adsorbed.
► It has a much higher affinity and Vmax for Pi-uptake than many other hydrophyte.