luation of cardinal temperatures and germination responses of four ecotypes of Bunium persicum under different thermal conditions

ABSTRACT: Considering the importance of germination on plants’ domestication processes, cardinal temperatures’ determinations appear to be a major step. Black cumin (Bunium persicum) is an advantageous medicinal plant which is forced into the endangered plants group because of inappropriate management practices and the lack of any published information about the cardinal temperatures effects on this species germination. In order to investigate germination response of of Black cumin to different temperatures, an experiment was conducted with four ecotypes of Bunium persicum (including, CE2, CE4, CE8, and CE9 ecotypes) from different parts of Iran at nine levels of temperature (4, 8, 12, 16, 18, 20, 24, 28, and 32 °C). Three models were fitted to determine the germination responses to temperature and comparing the efficiency of each model. Results indicated different correlations among the observed and simulated germination rate values for all ecotypes. Calculated values by the Intersected-line model (ISL) revealed the values from 0.35 to 3.33 °C for the base, 16.19 to 22.14 °C for the optimal, and 29.74 to 31.52 °C for the maximum temperatures. Fitted Quadratic Polynomial Model (QPN) showed significant correlation between the observed and simulated values for CE8 and CE9 ecotypes, but not for CE2 and CE4. According to the results of the five parameters of the beta model, cardinal temperatures for the evaluated ecotypes are similar to the calculated values with Quadratic Polynomial Model to some extent. Generally, ecotypes from the elevated habitats showed lower base, optimal, and maximum temperatures.