Germination modeling of Eryngium caeruleum seeds with hydro thermal time model

This study was conducted to evaluate the effect of temperature and moisture on germination of Eryngium caeruleum seeds as factorial experiment in a completely randomized design with three replications at weed science laboratory, college of agriculture and natural resources, university of Tehran. Factors were seven temperatures (5, 10, 15, 20, 25, 30 and 35°c) and seven levels of moisture (0, -2, -4, -6, -8, -10 and -12 bar) and hydro thermal time model used for description of Eryngium caeruleum germination. Germination parameters including base temperature (Tb), optimum temperature (To), the minimum moisture needed for start of germination (Wpb), decreasing coefficient (b) and standard deviation (Sigma) were obtained 2.39, 23.52, -0.93, 0.13 and 0.34 respectively, affected by different levels of temperature and moisture by using hydro thermal time model. The results also showed that germination percentage and rate increased up to -4 bar in base temperature and these germination characteristics reached to their highest level in optimum temperature. According to the results of this study, it can be said that the seeds of Eryngium caeruleum do not have resistance to the water stress at very low and very high temperatures, and have the maximum resistance at 20°c