From cone to seedling: Reproductive biology of Juniperus drupacea at its westernmost distribution limit

Abstract Juniperus drupacea is a Tertiary relict, dioecious tree, rare in Europe, found exclusively in Greece; its primary population located in Parnon Mt. (Peloponnese). In Europe, the species is considered as Endangered by the IUCN Red List, facing primary threats such as sapling grazing, timber overexploitation, fire and climate change. Data on cone/seed morphometric traits and seed viability/germination are analyzed with a focus on the implications for restoration and conservation efforts. Cones were collected in October–November of 2020–2023. The average cone mass is 3539.0 ± 95.5 mg, with each cone containing 1–5 viable seeds (mean of 2.3 seeds/cone); the average seed mass is 33.9 ± 2.6 mg. Seed germination was studied under constant (10, 15, 20 °C) and alternating (20/10, 25/15 °C) temperatures, after eight pre-chilling regimes (0, 4, 8, 12, 16, 20, 24 and 32 weeks) at 5 °C, both in continuous darkness or under light/dark (12 h photoperiod); the effect of GA 3 , with 16 weeks of pre-chilling or without pretreatment was also tested. Viability of seeds stored in a Seed Bank was assessed using the tetrazolium test (TTZ). The optimal seed germination was observed at 15 °C, while both pre-chilling (up to 16 w) and GA 3 treatment lead only to an increased germination rate. Seeds are light-indifferent, exhibit orthodox storage behavior, remaining viable for long periods (> 15 years). Seed storage within cones is more effective than in the form of exposed, ‘naked’ seeds. Based on our field observations, seedlings exhibit a high mortality rate during their first year.