Germination requirements of the endangered cliff-dwelling Primula palinuri Petagna and implications for conservation

Primula palinuri, an endangered plant species strictly confined to the coastal limestone cliffs of southern Italy, represents a key Mediterranean endemic threatened by habitat loss and environmental stressors. This study investigated the effects of temperature, salinity, water stress, and burial depth on its seed germination. Germination was favoured by cool temperatures, with an optimum at 15 °C. Rates significantly declined at both 5 °C and 25 °C. Increasing salinity markedly inhibited germination, confirming the species’ sensitivity to salt stress. Water stress experiments demonstrated that P. palinuri requires high soil moisture for successful germination, with total inhibition under moderate (- 0.4 MPa) to severe drought conditions (- 1.5 MPa). Burial depth negatively affected seedling emergence, likely due to the small seed size and light-dependency. These results underline the species’ narrow ecological requirements, emphasising the need for careful habitat selection in conservation actions, favouring moist, shady, and salt-protected microsites with shallow seed placement.