Determining the Dormancy Type of the Endangered Linum mulleri by Testing 7000 Seeds

Linum mulleri is an endemic taxon of southwestern Sardinia (Italy), categorised as Endangered (EN) on the IUCN Red List and included in Annexes II and IV of the Habitats Directive (92/43/EEC) as priority species for conservation. This study investigated the germination ecophysiology of L. mulleri and the possible presence of dormancy by using 7000 seeds, providing useful information for conservation strategies. The germination response of fresh seeds was evaluated under different temperatures, photoperiods, pre-treatments [cold stratification (C); warm stratification (W); W+C; C+W+C; dry after-ripening (DAR)], and different gibberellic acid (GA₃) concentrations. L. mulleri germinated under controlled conditions, particularly at 15 and 20 °C, while germination percentages (GP) never exceeded 5% at 5 and 30 °C. C and C+W+C induced secondary dormancy, delaying germination, whereas W, DAR, and GA₃ stimulate it. Light and dark incubation showed no significant differences in regards to GP. W, DAR, and 250 mg/L GA₃ effectively overcame physiological dormancy (PD), expanding the germination temperature range to below 10 and above 25 °C. These responses suggested type 3 non-deep PD, as germination temperatures extended from a moderate range to both low and high temperatures. Analyzing 7000 seeds provided crucial information regarding dormancy and germination strategies, supporting both ex situ and in situ conservation efforts.