The effect of temperature on some germination index of invasive plant of Centaurea balsamita and determination of its germination cardinal temperatures.
In order to evaluate the germination characteristics and cardinals temperatures in invasive plant of Centaurea balsamita, a laboratory experiment as a completely randomized design with four replications was conducted in Weed Research Laboratory, Faculty of Agriculture Ferdowsi University of Mashhad in 2014. Treatments consisted of 8 constant temperatures (1, 5, 10, 15, 20, 25, 30, 35 and 40°C). The characteristics such as percentage of seed germination, seedling vigour index, rate of seed germination, dry weight of radicle and plumule and plumule, radicle length were recorded. The seeds of Centaurea balsamita were monitored for variability in germination criteria based on two regression models namely Quadratic Polynomial Model and Intersected-Lines models. The highest germination percentage and germination rate was obtained in 20°C. The highest root length, shoot length, root and shoot dry matter was obtained in 25°C. Based on the regression between germination rate and temperature in Centaurea balsamita, the cardinal temperatures (Tbase, Topt and Tmax) were (1.44, 1.26), (22.8, 19.8) and (38.4, 38.2)°C. The results showed that Quadratic Polynomial Model was estimated better than Intersected-Lines model in terms of cardinal temperature.