Determination of cardinal temperatures of germination in three species of pigweed (Amaranthus sp.)

This study was carried out to evaluate the cardinal temperatures of germination of three Amaranth species (Amaranthus retrouflexus L.), (Amaranthus viridis L). and (Amaranthus blitoides S. Watson). The experiment was conducted as a completely randomized design with nine temperatures (5, 10, 15, 20, 25, 30, 35, 40 and 45) and four replications at Weed Science Research Laboratory of Ferdowsi University of Mashhad. Sseed germination percentage and rate was calculated and regression models were used to evaluate the results and determine cardinal temperatures. Based on the results, among the nonlinear regression models, the intersected lines and quadratic polynomial models with respect to the highest coefficient of determination (R2) showed the best fitting of germination rate of seeds. Accordingly, the intersected lines model was more preferred. generally over the minimum temperature, optimum temperature and maximum temperature using intersected-lines model for green pigweed of 4.86, 25.56 and 45.76 ° C, respectively. Red root pigweed was calculated 6.65, 30.56 and 51.6 ° C, respectively, and was estimated to be 9.22, 34.39 and 50.66 ° C for prostrate pigweed, respectively. The results of this study showed that sow seed germination was carried out over a wide range. All three species were able to germinate between 10 and 45 ° C.