Light and temperature requirements for germination in the Mediterranean shrub Lavandula stoechas (Lamiaceae)

Available studies are far from giving a complete figure for the germination requirements of many Mediterranean Basin species. In this study, we investigated the germination properties of Lavandula stoechas L. (Lamiaceae) in response to different light and temperature regimes. We performed comprehensive experiments to test the effect of fixed and alternating temperatures, dark versus light conditions, and thermodormancy or thermoinhibition on several germination properties in three populations of L. stoechas from southwestern Turkey. Germination patterns showed a substantial variation among populations. Germination percentage was higher in the light conditions than in the dark at most temperatures, and alternating temperatures substituted light for the germination. The requirement of L. stoechas seeds to light for germination gradually increased through lower and higher temperatures than 15 °C. High temperature (30 °C) reduced the germination percentage to zero. However, in the presence of light, seeds were able to germinate after transferring to the optimum temperature (thermoinhibition), but this was not the case in darkness (thermodormancy). Seed germination in L. stoechas was stimulated by light, suggesting that germination has a phytochrome-mediated response. Our study makes an inference to the fire-environment interactions in the germination of Mediterranean seeder species by showing that both light and alternating temperatures stimulate germination in L. stoechas, a species well-known with its fire-related germination. Comprehensive germination studies are required for a better understanding of the early life-stage adaptations of plants to Mediterranean conditions, and for developing more robust strategies for conservation and ecosystem restoration.