Quantification of the response of germination rate to temperature in sesame (Sesamum indicum)

The main objective of this study was to develop and introduce an appropriate model(s) to quantify the response of germination rate (GR) to temperature (T) and to determine the cardinal temperatures and physiological hours (f(o)) required for seed germination to occur. Dent-like and segmented models were used to describe the relationship between GR and T. Results indicate that the response of sesame GR to T can be satisfactorily described by either model. Estimates for the cardinal temperatures using the dent-like model were 13.5 degrees C for base temperature (T-b), 35.8 degrees C for the lower optimum temperature, 39.4 degrees C for the upper optimum temperature and 47.0 degrees C for the ceiling temperature (T-c) with f(o) estimated as 6.61 hour(-1) (R-2 = 0.98, RMSE = 3.08 hour(-1)). For the segmented model estimates were 13.5, 36.8, 48.5 degrees C and 6.34 hour(-1) for T-b, optimum temperature, T-c and f(o), respectively (R-2 = 0.97, RMSE = 3.52 hour(-1)). Using both models, the thermal time [TT = (T-o1 - T-b)f(o)] required to reach 50% maximum germination was 6.3 degrees C days.