evaluation of nonlinear regeression models in quantifying germination rate of medicinal pumpkin (cucurbita pepo l. subsp. pepo. convar. pepo var. styriaca greb), borago (borago officinalis l.) and black cumin (nigella sativa l.) to temperature

selection of an appropriate model is important for quantifying response of germination rate to temperature and determination of cardinal temperatures. this study was done to evaluate different nonlinear regression models to describe response of germination rate to temperature in medicinal pumpkin, borago and black cumin. the regression models were dent-like, segmented, beta, curvilinear, quadratic and cubic. root mean square of error, coefficient of determination, correlation coefficient and regression of predicted values versus observed ones were used to find the appropriate model(s). dent-like and beta models were superior compared to other models in medicinal pumkin and black cumin. in borago, dent-like, beta and curvilinear models were superior. it was concluded that these models can be used to quantify response of medicinal pumpkin, borago and black cumin germination to temperature and to obtain cardinal temperature of germination. these parameters are required to predict medicinal pumpkin, borago and black cumin germination and emergence.