Cardinal temperatures for seed germination of six ecotypes of Plantago major

Harvesting of medicinal plants from their natural habitats, put them in danger, hence their domestication is needed. In this context, knowledge of the properties of these plants, including the cardinal germination temperatures are necessary. In order to determine the cardinal temperatures and the effect of temperature on the percentage and rate of germination in Plantago major ecotypes (Birjand, Ghaen, Torbathydarieh, Mashhad, Kalat and Bojnord) an experiment was conducted based on factorial in a completely randomized design with 9 temperature levels (5, 10, 15, 20, 25, 30, 35, 40 and 45 °C) and four replications in Crop Physiology Laboratory, Ferdowsi University of Mashhad in 2013. To determine the cardinal temperatures Intersected-Lines Model and Five-Parameters Beta Model were used. Results showed that maximum germination percentage was obtained at 30 °C while maximum germination speed achieved at 35 °C in Bojnourd and Birjand ecotypes, respectively. The highest germination percentage was observed in Birjand ecotype at the temperature range of 20 to 35 °C. Based on models fitted depending on the ecotype, cardinal temperatures  (minimum, optimum and maximum) germination were determined (6.3 to 9.8, 1.8 to 5°C) ,(31.1 to 35.9, 28.6 to 35.2°C) and (43.3 to 45.1, 45 to 45.6 °C) of Intersected-lines and Five-Parameters Beta Model, respectively. Diversity in cardinal temperature of plantago major ecotypes could be due to different environmental conditions where they were evolved and adapted