Light, temperature, dry after-ripening and salt stress effects on seed germination of Phleum sardoum (Hackel) Hackel

Phleum sardoum is an endemic psammophilous species of Sardinia, growing exclusively on coastal sandy dunes. The presence of glumes on seed germination, germination requirements at constant (5-25°C) and alternating (25/10°C) temperatures, both in the light (12/12 h) and in the dark, the effect of a dry after-ripening period (90 days at 25°C), the salt stress effect (0-600 mM NaCl) and its recovery on seed germination were evaluated. The presence of glumes reduced final germination percentages. For fresh naked seeds, high germination percentages were observed at 10°C. Dry after-ripening increased germination rate at low temperatures, but did not affect final germination percentages. NaCl determined a secondary salt-induced dormancy which recovery interrupted only partially. Our results highlighted that this species has its optimum of germination during autumn-winter when, under a Mediterranean climate, water availability is highest, the dry summer period far and soil salinity levels are minima