Temperature is an important environmental factor controlling seed germination. The temperature response of D. cordata seeds was assessed on a thermal time basis in order to evaluate this model describing germination behavior of the seeds under different thermal regimes. Seed response to light was also tested, and the results led to the conclusion that germination was promoted by white light. Base, optima and ceiling temperatures for germination of D. cordata were, respectively, 17.1 ºC, 26 ºC and 33.4 ºC. Since germination rate was linearly related to temperature, the thermal time model can be used to assess temperature dependence of seed germination in D.cordata. Possible acquisition of seed dormancy during imbibition may not allow a good fit of cumulative germination under some temperature regimes, and other models must be used.
photoblastic reaction; temperature; thermal time; weed
