Quantifying cardinal temperatures and thermal time for seed germination of Papaver dubium and P. rhoeas

ABSTRACT Background Temperature plays a key role in plants distribution. Cardinal temperatures are important parameters for plant population dynamics models. Aims This study was conducted to estimate the cardinal temperatures and other parameters in relation to temperature using three non-linear regression models (segmented, dent-like and beta) to project the germination rate and temperature relation of Papaver dubium and P. rhoeas. Methods An optimisation method was used to fit the models and their statistical parameters. Their efficiency was compared with the coefficient of determination (R2), root mean square error (RMSE) and the Akaike Information Criterion. Results Calculated cardinal temperatures differed for different germination percentiles (10, 30, 50%). The time required to 50% germination of both P. dubium and P. rhoaes was more accurate than the time required to 10% and 30% germination between observed and predicted values. According to the outputs of the segmented model, base, optimum and maximum temperatures of P. rhoeas were 1.9°C, 22.4°C and 39.6°C, respectively. The corresponding values for P. dubium were 2.1°C, 22.1°C and 39.1°C. Conclusions The parameters related to temperature provide the basic information to determine the time needed for germination and to project potentially suitable areas for invasion. The segmented model is appropriate for the estimation of the cardinal temperatures of both Papaver species.