temperature and photoperiod are abiotic variables that directly influence aquatic macrophyte production. they also determine the geographic distribution of the species and affect community structure. the aim of this study was to evaluate the growth of pistia stratiotes in different temperature and photoperiod regimes. p. stratiotes plants were conditioned in growth chambers with controlled temperature and photoperiod. six treatments were used: 1 (15 oc/8 h photoperiod); 2 (15 oc/12 h); 3 (25 oc/8 h); 4 (25 oc/12 h); 5 (30 oc/8 h) and 6 (30 oc/12 h). the highest biomass gain occurred with treatment number 4 which showed significant differences (p<0.05) compared to treatments number 1, 5 and 6. in treatments 1, 5 and 6 the final biomass was lower than the initial biomass of p. stratiotes. the greatest biomass reduction occurred in treatment number 6 which was significantly lower than in treatments 2, 3 and 4. the highest sprout production was observed in treatments at 25 oc, while in treatments at 15 oc and 30 oc sprouting was greatly reduced. we conclude that temperature and photoperiod influence p. stratiotes growth and higher growth rates occurred at 25 oc and 12-hour photoperiod.