Abstract
Cyperus arenarius Retz. (Cyperaceae) is a low stoloniferous perennial of coastal sand dunes. We examined the effects of salinity (0, 100, 200, 300, 400 and 600 mM NaCl), temperature (10/20, 15/25, 20/30 and 25/35 degrees C) and light (12/12 h dark/light and 24 h dark) on seed germination of C. arenarius. Freshly collected seeds showed highest germination in distilled water and 100 mM NaCl at 25/35 degrees C. However, germination in 100 mM NaCl solution was about 25% slower than in distilled water. About 50% germination inhibition was observed at 200 mM NaCl and no seed germinated above 300 mM NaCl. Under optimal conditions, germination in complete darkness was about half of the 12-h photoperiod. About 50% of the un-germinated seeds from 400 and 600 mM NaCl recovered when transferred to distilled water (enforced dormancy), 35% remained un-germinated but viable (induced dormancy), while 15% were dead. Seeds from non-saline and complete dark treatment showed dark-induced dormancy (about 40%) whereas, seeds from saline conditions had about 20-25% higher salt-enforced dormancy than the 12 h photoperiod. Ecological significance of the effects of salinity, temperature, light and their interactions on seed germination and recovery of C. arenarius is discussed.