Effect of various temperatures on germination behavior of Thymus daenensis (Elam ecotype)

Thymus daenensisis endemic medicinal plant of Iran and belong to Lamiaceae family.In this study germination behavior of Elamecotype of Thymus daenensis subsp. daenensis under various temperatures was studied. Seeds were exposed to nine constant temperatures ranging from 3°C to 40°C. Analysis of variance revealed clear differences in temperature requirements for seed germination in the ecotype. To determine cardinal temperature, Germination rate-temperature relationship was considered. Two regression models; Intersected lines and Plateau were used to describe these relationships.The result was evaluated through regression coefficient (R2) and root mean square error (RMSE). The comparison results showed that the best model was plateau model. The based temperature was predicted 1.4°C, the optimum germination rate were within the ranges of 20°Cto 24.7°C and ceiling temperature 39.68°C in this ecotype.Temperature had a significant effect on germination indices such as coefficient uniformity germination, germination index, daily germination speed, mean germination timemeangermination daily and etc. Result in the present study reveals that Elam ecotype was adapted to lower temperatures in order to avoid summer drought and to benefit winter humidity.