Chemical applications, scarification and stratification effects on seed germination of rare endemic Verbascum calycosum hausskn. ex Murb. (Scrophulariaceae)

Verbascum calycosum is an endemic plant species having considerable narrow distribution in Erzincan (Turkey) region. This species is known from only a single population and its habitats are highly threatened due to intensive human activities and soil erosion. In this study, the germination behavior of V. calycosum under different concentrations of NaCl, HCl, KNO3, GA3 (100 and 200 μM), hot-cold stratification and mechanical scarification were investigated. Seeds were exposed to a photoperiod of 8 h light/16 h dark with a 23/18 °C thermoperiod. Germination rates increased with GA3-100 μM (39%), GA3-200 μM (54.5%), mechanical scarification (34.5%) and cold stratification treatments (+4 °C, 23.25%; -20 °C, 18.25%) on the other hand, KNO3, NaCl, HCl and stratification with hot water treatments have decreased germination rates significantly when compared to the control (12.25%). Increased germination after GA3 application and mechanical scarification indicated that seeds of V. calycosum exhibited both non-deep and intermediate physiological dormancy as well as physical dormancy due to its hard seed coat. The highest speed of germination index was obtained at cold stratification of +4 °C and -20 °C (10.3). This study represents first report about seed dormancy and germination characteristics of V. calycosum. Overall, these results will provide valuable data for ex situ conservation of this rare endemic plant. © 2018 Academic Press.