Cardinal germination temperatures of some medicinal plant species

The germination behavior of 11 medicinal plant species under different temperatures was studied. Seeds of all species were exposed to eight constant temperatures ranging from 5—40 °C. A linear model was applied to describe the germination rate-temperature relationship. Tested species showed clear differences in temperature requirements for seed germination. The highest germination percentage was observed within the ranges of 15—25 °C for Marrubium vulgare L., 15—30 °C for Origanum majorana L., 10—30 °C for Hyssopus officinalis L. and Silybum marianum L., 10—25 °C for Thymus daenensis Celak subsp. daenensis and Ocimum basilicum L. Germination of most species ceased or highly declined at temperatures of 35 °C. The highest germination rate was observed within temperature ranges of 15—30 °C for Nepeta racemosa Lam., Oenothera biennis L. and H. officinalis, 10—25 °C for O. basilicum and Salvia nemorosa L., 20—25 °C for O. majorana L. and T. daenensis and 10—30 °C for S. marianum. The lowest base temperature was observed for Salvia sclarea L., S. nemorosa, H. officinalis and Centaurea benedicta (L.) L. All medicinal species studied in this research had a low, below 5 °C, base temperature. Optimum temperature ranged from 13—24 °C, and the lowest optimum temperature belonged to C. benedicta. These germination requirements are insufficient to make a general conclusion for introducing the species into cultivation, however, these data provide basic temperature requirements for further research.