Document Type : Research Paper
Authors
1
Research Institute of Forests and Rangelands, Tehran, Iran
2
Natural Resources Gene Bank, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization, Tehran, Iran
3
Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran
4
Bank of Research Institute of Forests and Rangelands, Research Agricultural, Education and Extension Organization, Tehran, Iran
Abstract
To evaluate the germination characteristics and determine the cardinal germination temperatures of Thymus kotschyanus, T. daenensis and T. lancifolius, a factorial experiment was conducted in 2023, at the Seed Technology Research Laboratory of the Natural Resources Gene Bank of Iran. This experiment, designed in a completely randomized format with three replications, aimed to evaluate the germination characteristics and determine the cardinal temperatures of germination of three thyme species: Thymus kotschyanus, Thymus daenensis, and T. lancifolius. The seeds were exposed to a range of temperatures from 5 to 40°C, a crucial step in understanding their germination behavior. Three non-linear regression models, including dent-like, segmented, and beta, were employed to characterize the germination rate response of three thyme species across eight temperature levels. Statistical indices such as root mean squared error (RMSE) and coefficient of determination (R²) were utilized to compare the models. Results from this experiment demonstrated that the studied thyme species exhibited similar germination peaks due to similar initial growth rates. Based on the results, the dent-like model provided the best fit for T. lancifolius with a basic temperature of 7.58 °C, a lower optimum temperature of 15.10 °C, an upper optimum temperature of 15.65°C, and a ceiling temperature of 36.19 °C, with R² and RMSE values of 0.97 and 0.15, respectively. For T. kotschyanus, the dent-like model with a basic temperature of 5°C, lower optimum temperature of 17.47°C, upper optimum temperature of 19.73°C, and a ceiling temperature of 34.24 °C, and R² and RMSE values of 0.92 and 0.08, respectively, also showed a good fit. However, for T. daenensis, the segmented model with an essential temperature of 6°C, optimum temperature of 20°C, and ceiling temperature of 36°C, and R² and RMSE values of 0.99 and 0.06, respectively, provided the most reliable fit. Conclusively, the germination temperature range for all three thyme species was 10 to 35°C, with an optimal germination temperature of 15 to 20°C. These results emphasized the high adaptability and promising cultivation potential of the three thyme species in temperate natural resource areas, offering a significant implication for future agricultural practices.
Keywords
Main Subjects
)