Abstract
Aim of study: The purpose was to determine the type of dormancy and the optimal germination conditions of Phillyrea angustifolia (Oleaceae) seeds.Area of study: Germination requirements of P. angustifolia seeds collected from wild plants growing in the province of Ávila (Central Spain) were studied.Materials and methods: Seed water uptake was measured. Seeds with and without an endocarp were germinated at different temperatures, and several treatments were tested.Main results: The lignified endocarp interferes mechanically with the emergence of the radicle, and the treatments that achieved the highest germination percentages were the total removal of the endocarp with pliers (84%) or the immersion in liquid nitrogen for 1 min (97%). Scarification with concentrated sulphuric acid did not significantly increase germination compared to the control seeds, and treatments with dry heat or wet heat were detrimental to seed germination. The optimum temperature for germination was 15 ºC. A pre-sowing treatment of soaking in distilled water for 24 h slightly increased germination speed. Neither cold stratification at 5 ºC nor soaking in a gibberellic acid solution improved seed germination. Research highlights: Phillyrea angustifolia seeds have physiological dormancy – that is, the embryo does not have enough growth potential to overcome the mechanical restriction of the lignified endocarp. The seeds do not exhibit physical dormancy, given their water-permeable lignified endocarp. Our results suggest that the optimum germination protocol for P. angustifolia would be the total removal of the endocarp or immersion in liquid nitrogen for 1 min, followed by immersion in distilled water for 24 h and then seed incubation at 15 ºC in light or darkness.
Highlights
Plants living in Mediterranean ecosystems face serious environmental constraints
Our results suggest that the optimum germination protocol for P. angustifolia would be the total removal of the endocarp or immersion in liquid nitrogen for 1 min, followed by immersion in distilled water for 24 h and seed incubation at 15 oC in light or darkness
Seeds of P. angustifolia without an endocarp imbibed water quickly after 24 h, and seed mass increased by 47% (Figure 2)
Summary
Plants living in Mediterranean ecosystems face serious environmental constraints. These plants cope with extreme summer droughts and frequent fires that play an important role in such ecosystems (Chaves et al, 2002). (Oleaceae), narrow-leaved mock privet or evergreen privet, is a small tree that appears scattered in dense evergreen Mediterranean forests and tall shrublands. It grows in well-preserved habitats across warm and dry areas and plays an important role in post-fire ecological dynamics (Herrera et al, 1994; Vitale et al, 2007). Many of the natural and semi-natural forests in which P. angustifolia grows are under decline due to climate change and centuries of
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