Seed germination characteristics of Phragmites communis:: Effects of temperature and salinity

Phragmites communis Trin. has a wide ecological and geographical amplitude in Tunisia and grows under a variety of environmental conditions. A laboratory experiment was performed to evaluate the effect of temperature and salinity on the germination of P communis. The germination response of the seeds in darkness were determined over a wide range of temperatures (between 5 degrees C and 40 degrees C) and salinity (between 0 mM and 500 mM NaCl). We analysed the responses of seeds to salinity at the optimum germination temperature. Temperatures between 10 degrees C and 30 degrees C appeared favourable for the germination of this species. The optimum temperature was 20 degrees C. To assess the effect of temperature on germination rates, the reciprocal of time to 50% germination was calculated and regressed against temperature. Based on the regression, the minimum temperature beyond which no germination is expected was 6.7 degrees C. Salt stress decreased both the germination percentage and germination speed (increase of the mean time-to-germination, MTG). The ability of R communis to maintain a germination capacity in hypersaline conditions (400 mM) showed that this species can germinate on salt-soils.