Cardinal temperatures and thermal requirements for germination of cineraria seed

Effects of temperature on the rate of germination, measured as the reciproc al of the time taken for half the population to germinate, were studied in cineraria cvs Cindy Blue and Cindy Dark Red. The base, optimum and maximum temperatures for germination were derived respectively as 1.6, 24.8 and 37. 8 degrees C in cv. Cindy Blue, close to T-b = 1.9, T-o = 24.5 and T-m = 38. 4 degrees C in cv. Cindy Dark Red. All seeds of each cultivar had a common base temperature but needed different thermal times to germinate. Seed of c v. Cindy Dark Red began to germinate after ca. 30 degrees Cd compared with 35 degrees Cd required by cv. Cindy Blue. A thermal time of ca. 50 degrees Cd was required for half the population to germinate in each cultivar and t he thermal requirement for germination fraction >0.5 was similar in both cu ltivars. The base and maximum temperatures for germination were similar to those determined previously for leaf initiation and flower development.