Seed Science Society of Iran Iranian Journal of Seed Science and Technology 2322-2646 6 1 2017 05 22 The Estimation of cardinal temperatures in common Marigold (Calendula officinalis L.) The Estimation of cardinal temperatures in common Marigold (Calendula officinalis L.) 39 48 113286 10.22034/ijsst.2017.113286 FA N. Khaliliaqdam Assistant Professor/ Department of Agriculture, Payame Noor University, Tehran, Iran. T. Mir-mahmoodi Assistant Professor/ Agronomy and Plant Breeding Department, Mahabad Branch, Islamic Azad University, Mahabad, Iran. Gh.R. Bakhshi Khaniaki Professor/ Department of Agriculture, Payame Noor University, Tehran, Iran. Journal Article 2016 10 25 Temperature is one of the most effective and important environmental agents on seed germination, thus interaction effect of germination with temperature is very important in prediction of germination time and modeling especially. A completely randomized design experiment performed in seed research laboratory of Islamic Azad University, Mahabad Branch with four replications which temperature treatment were 11 levels as: 3, 5, 7, 10, 15, 20, 25, 30, 35, 40 and 45 ⁰C. Three nonlinear regression models as Beta, 5-Parametric Beta and Segmented functions tested. Results revealed that temperature had a significant effects of rate, uniformity and germination percent. The highest uniformity and germination percentage were detected in 15 ⁰C, but the highest value of rate of germination obtained in 20 ⁰C.  Although, there was no significant difference between practiced models in estimation of cardinal temperatures, however, the segmented model which had the less RMSE, CV and the more R² and correlation coefficients than the others, was a better model and thus, cardinal temperatures including base, optimum and ceiling temperatures were 3.35, 20.84 and 40.94 ⁰C, respectively. Also, the maximum germination rate (r_max ) was  0.010 h-¹. Temperature is one of the most effective and important environmental agents on seed germination, thus interaction effect of germination with temperature is very important in prediction of germination time and modeling especially. A completely randomized design experiment performed in seed research laboratory of Islamic Azad University, Mahabad Branch with four replications which temperature treatment were 11 levels as: 3, 5, 7, 10, 15, 20, 25, 30, 35, 40 and 45 ⁰C. Three nonlinear regression models as Beta, 5-Parametric Beta and Segmented functions tested. Results revealed that temperature had a significant effects of rate, uniformity and germination percent. The highest uniformity and germination percentage were detected in 15 ⁰C, but the highest value of rate of germination obtained in 20 ⁰C.  Although, there was no significant difference between practiced models in estimation of cardinal temperatures, however, the segmented model which had the less RMSE, CV and the more R² and correlation coefficients than the others, was a better model and thus, cardinal temperatures including base, optimum and ceiling temperatures were 3.35, 20.84 and 40.94 ⁰C, respectively. Also, the maximum germination rate (r_max ) was  0.010 h-¹. https://ijsst.areeo.ac.ir/article_113286_8829992c3c724ce060da9a1c88d6fa9b.pdf