Basil has many applications in industrial, cosmetic, pharmacy, foods, perfumery and culinary. Therefore, understanding of its temperature needs is necessary for its appropriate germination, growth and development. In present study three regression models (Intersected-lines model, Quadratic Polynomial model and Five-Parameters Beta model) were used for describing the relationships between germination rate and temperature in green and purple cultivars of basil.

 Temperature treatments were included of nine constant temperatures including 0, 5, 10, 15, 20, 25, 30, 35 and 40 °C. The experiment was conducted at seed research laboratory of University of Birjand, based on a completely randomized design with four replications. Germination of purple basil started from 10 °C (6%), reached to maximum at 20 °C (73%) and then decreased with increasing temperature until reached to 0% at 40 °C. The highest amount of germination rate was obtained at 25 °C (10 seed day⁻¹), followed by 20 °C treatment. Intersected-lines model was found to be the best model to predict germination rate of purple basil (R² = 0.9). Based on model output, the amounts of base temperature (T_b), optimum temperature (T_o) and maximum temperature (T_m) for germination of purple basil were 7, 24.97 and 41.84 °C, respectively. Germination of green basil was started from 10 °C (15%), followed by 60–67% in 15-30 °C and finally decreased to 7% in 40 °C. The highest values of germination rate were obtained at 25–30 °C (9.4–9.65 seed day⁻¹). Intersected-lines model showed most suitable fitness in the case of green basil (R² = 0.91). Based on the regression between germination rate and temperature, the cardinal temperatures (T_b, T_o and T_m) for green basil were 6.11, 28.97 and 43.58 °C, respectively. In addition, temperature range (T_m–T_b) for purple and green basil was obtained 34.84 and 37.47 °C, respectively. Totally, the use of the three models confirms the generally known fact that basil needs higher temperatures for germination.

Sophia
Managing Editor
Herbal Medicine: Open access journal
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