Estimation of Cardinal Temperatures of (Echium amoenum) with Application of Regression Models

In order to investigate the germination characteristics and cardinals temperatures of Echium amoenum, a laboratory experiment was conducted in Faculty of Agriculture Ferdowsi University of Mashhad in 2009. The layout of experiment was a completely randomized design with 6 replications. Treatments consisted of 8 constant temperatures (5, 10, 15, 20, 25, 30, 35 and 40 oC). The characteristics such as percentage of seed germination, rate of seed germination, dry weight of radicle and plumule and plumule, radicle length were recorded. The seeds of Echium amoenum were monitored for variability in germination criteria based on two regression models namely: Five- parameters Beta (FPB) and Intersected-Lines (ISL) models. The effect of temperature on germination percentage and germination rate, dry weight of radicle and plumule, and plumule, radicle length were significant. The highest germination percentage and germination rate were obtained in 25 0C. Based on the regression between germination rate and temperature in Echium amoenum, the cardinal temperatures (Tbase, Topt and Tmax) were: 4.99-5.66, 23-29.23 and 39.12-40.36 0C. The results showed that the Five-parameters Beta model was estimated better than Intersected-Lines model in terms of cardinal temperature.