Interpopulation variation in seed germination of five Mediterranean Labiatae shrubby species

The aim of this work was to determine seed germination characteristics of different populations of five Mediterranean Labiatae species: lavender (Lavandula stoechas), oregano (Origanum vulgare), and three species of thyme (Thymus mastichina, T. vulgaris, and T. zygis). Correlations of final germination percentage of each population with seed weight and various geographic parameters (longitude, latitude, and altitude) were studied. For each species, final germination percentages were highly variable depending on the population, ranging from 16 to 95% for Lavandula stoechas, 4-95% for Thymus zygis, 13-90% for T. vulgaris, 35-95% for T mastichina, and 21-91% for Origanum vulgare. Similarly, germination rate (T-50) varied significantly. A significant relationship between seed weight and final germination percentage was identified for the populations of L. stoechas and O. vulgare. Moreover, germination percentages correlated significantly with altitude in T mastichina, and with longitude in O. vulgare. In addition, seed weight showed a significant relationship with longitude in O. vulgare and with latitude in T. mastichina.