Determination of Cardinal Temperatures and Evaluation of Seed Germination Response of Five Seed ecotypes of (Hyoscyamus SPP.) Medicinal Plant to Temperature and Water Potential

The Henbane (Hyoscyamus SPP.) belongs to the potato genus and due to the presence of alkaloids such as atropine, hyoscyamine and scopolamine, it affects the human nervous system. Among the annual and perennial species of this genus, five of them are endemic in Iran. The aim of this study was to determine the cardinal temperatures and evaluate the germination response of five seed ecotypes (Hyoscyamus SPP.) to water temperature and potential. For this purpose, a factorial experiment was conducted in a completely randomized design with four replications. Experimental treatments were run according to eight temperature levels (5, 10, 15, 20, 25, 30, 35, and 40°c) and six water potential levels (0, -0.2, -0.3, -0.4, -0.6 and -0.9 MPa). The results showed that with decreasing water potential, the percentage and germination rate of Ecotypes decreased. Estimation of cardinal temperatures showed that the base temperature and ceiling temperature of the five studied Ecotypes were the same and were equal to 8 and about 40 ° C, respectively. Furthermore, the optimum temperature of these Ecotypes was recorded in the range of 25-35 ° C. The Dashty Ecotype had a wider optimum temperature range. According to R2 and RMSE statistics, the Dent-like model well describes the germination rate response of the studied ecotypes to temperature and water potential.