Seed germination, salt-stress tolerance, and the effect of nitrate on three Tyrrhenian coastal species of the Silene mollissima aggregate (Caryophyllaceae)

The Silene mollissima (L.) Pers. aggregate is part of section Siphonomorpha Otth. and currently comprises 11 narrow endemic species of the Western Mediterranean Basin. Three of these taxa (S. velutina Pourr. ex Loisel, S. ichnusae Brullo, De Marco & De Marco f., and S. badaroi Breistr.) have a distribution range centred in the northern Tyrrhenian area and occurring in coastal habitats. Inter- and intra-specific variability in the responses to light, constant (5–25 °C) and alternating temperatures (25/10 °C), salt (NaCl, 0–600 mmol/L), and levels of nitrate (KNO3, 20 mmol/L) under salt stress, as well as recovery of seed germination were evaluated for these species to more effectively support their in-situ and ex-situ conservation. Our results highlighted that the seeds of these three taxa were nondormant, and that light significantly improved their rate of germination, which was higher (>80%) at low temperatures (5–15 °C) and under the alternating temperature regime (25/10 °C), but decreased significantly...