Effect of temperature and cold stratification on seed germination of the Mediterranean wild aromatic Clinopodium sandalioticum (Lamiaceae)

A germination study was carried out on seeds of Clinopodium sandalioticum (Bacch. & Brullo) Bacch. & Brullo ex Peruzzi & Conti (Lamiaceae), a wild aromatic plant endemic to Sardinia. Seeds were incubated at a range of constant (5-25 degrees C) and an alternating temperatures regime (25/10 degrees C), with 12 hours of irradiance per day. The results achieved at 10 degrees C were also compared with those obtained after a period of cold stratification at 5 degrees C for three months. Final seed germination ranged from ca. 28% (5 degrees C) to ca. 72% (25/10 degrees C). A base temperature for germination (T-b) of ca. 5 degrees C and a thermal constant for 50% germination (S) of 89.3 degrees Cd were identified and an optimal temperature for germination (T-o) was estimated to be comprised between 20 and 25 degrees C. Cold stratification negatively affected seed viability and germination at 10 degrees C. Although a typical Mediterranean germination syndrome, could not be detected for C. sandalioticum seeds, these results were coherent with those previously reported for other Mediterranean Lamiaceae species.