Ecology of seed dormancy and germination of Carex divisa Huds.: Effects of stratification, temperature and salinity

Carex divisa is a patrimonial rhizomatous species and acts as an important component of grazed wet permanent grassland on the French Atlantic coast. This study treated three storage regimes (wet-cold, dry-cold and dry-warm), burial in soil, fluctuating temperature and salinity on seed germination of C. divisa. The seeds were dormant at maturity. No seed germinated after 2 and 6 weeks of dry storage under laboratory conditions prior to the onset of the stratification treatment. Thus, the effect of after-ripening was not evident in C. divisa. Germination rate of 11.3% started only in the wet-cold stratification treatment after 2 months. Seeds that had been stored under wet-cold conditions for 8 months had a higher germination than seeds stored under dry-cold and dry-warm treatments for the same length of time. Seeds of C. divisa tested at 10-20 °C in light had no marked dormancy cycle, but in darkness under a fluctuating temperature regime (10-20 °C), C. divisa seems to exhibit annual dormancy cycles. There were no differences in germination between fluctuating temperatures 10-20 °C and 15-25 °C after 12 months in the wet-cold treatment. No germination occurred at fluctuating temperatures 0-10 °C. The highest percent germination was observed in distilled water, followed by 50 mM L-1 NaCl. The highest NaCl concentration (250 mM L-1) was found to inhibit seeds germination.