Growth Dynamics of Pistia stratiotes in Temperate Climate

In order to understand the growth dynamics of the floating macrophyte Pistia stratiotes under natural conditions in a temperate climate, and the influence of higher levels of N and P concentrations in water on the specific growth rate, m, a number of experiments were carried out in two series. Series I: 29 determinations of m in the stationary growth stage using an oligotrophic medium were carried out. The experimental data was fitted by a function which rules cyclic processes in wetlands (R = 0.93), and a maximum m of 0.0395 day^–1 over the year was calculated. Series II: several batch experiments were carried out in Osaka 34° northern latitude, and in Montevideo 34°50' southern latitude. The transitory stage of growth dynamics for plants, which were transferred to a medium with higher concentrations of N and P, was considered. In this case, the Double Monod model with double inhibition affected by a constant term adequately explains the variations in m with R = 0.85 and 0.88 at 24°C and 29°C respectively.