A comparison of caesium uptake kinetics in eight species of grass

The Michaelis–Menten kinetic parameters (Imax, Km and Cmin) of Cs uptake were estimated using a solution-depletion method, after 0, 1 and 4 d K-starvation in eight mature grass species of different relative growth rates (Bromus sterilis L., Elymus repens (L.) Gould, Poa annua L., Lolium perenne L. var. ‘Taya’, Anthoxanthum odoratum L., Festuca gigantea (L.) Vill., Festuca ovina L. and Nardus stricta L.). There were species differences in Imax and Cmin, a positive relationship between Km and RGR (r2=0.53; p=0.03), and a negative relationship between Cmin and RGR (r2=0.89; p=0.001) in 0 d K starved plants. In general, Imax increased with K starvation, as previously reported for K uptake kinetics. Km increased with K starvation, contrasting with reported studies on K, and Cmin decreased, although all species did not respond similarly