Seed germination requirements of Hypericum scruglii, an endangered medicinal plant species of Sardinia (Italy)

Hypericum scruglii is an endangered endemic plant of Sardinia and the phloroglucinol compounds identified in this species have been reported to inhibit Human Immunodeficiency Virus activity. Seed banks are a genetic repository that effectively preserve taxa of conservation interest and they hold knowledge about the biology and germination eco-physiology of the taxa they preserve. The main goals of this study were to investigate the germination requirements of H. scruglii, to evaluate the seed viability after eight years of long-term conservation and to suggest an efficient protocol for germination. Seeds stored at -25 °C in the seed bank were tested at temperatures from 5 to 30 °C and 25/10 °C. Base temperature (Tb) and thermal time (θ50) for germination were estimated. H. scruglii seeds germinated over a wide range of temperatures, responding positively to high temperatures and 25/10 °C. Tb was estimated at 4.92 °C, and θ50 was estimated at 198.27 degree days. The high viability detected in seeds of H. scruglii allows us to suggest the use of seeds stored in a seed bank when fresh material for plant propagation is scarce. Our results provide new and useful baseline information for implementing conservation and multiplication strategies for this endangered medicinal plant.