MODELLING CARDINAL TEMPERATURES OF COMMON LAMBSQUARTERS GERMINATION BY THERMAL TIME APPROACH

In order to determine the effect of temperature on germination response and cardinal temperatures of common lambsquarters (Chenopodium album), germination of common lambsquarters seeds was modelled by the concept of thermal time. Seeds of C. album, were incubated to 6 constant temperatures (7, 12, 17, 22, 27 and 32 ºC). Results showed that the temperatures had highly significant on seed germination rate (P < 0.01). Among three nonlinear nested sigmoidal regression models (statistical distributions) used in estimate (3 and 4-parameter sigmoidal models and 4-parameter bounded Wibull function), the 4-parameter bounded Wibull model was found to be accurate to describe time course of the cumulative germination of C.album seeds at various sub- and super-optimal temperatures. In addition, among three non-linear regression models were fitted to germination rate data in cardinal temperatures of common lambsquarters assessment (triangular, dent-like and beta), the dent-like and beta models resulted the worst fit (with high RMSE amount: 0.0038, 0.0058 and low R2 values: 0.91, 0.85) respectively. Unlike, triangular model gave the better fit to germinated data ((with less RMSE 0.0028 and high R2 0.92) and non signifcant obtained F- observed= 0.98 from models comparison [triangular versus: dent-like]). Basic temperature of seed germination for common lambsquarters was estimated at 4.58 ºC. Also, the optimum temperature for mid germination rate was found at 20.94 ºC. At the end, ceiling temperature and biological time for 50% common lambsquarters seed germination was determined at 40 ºC and 47.70 hour, respectively.

MODELLING CARDINAL TEMPERATURES OF COMMON LAMBSQUARTERS GERMINATION BY THERMAL TIME APPROACH Keywords:

Ceiling temperature , dent-like model , triangular model , biological time , mid germination rate , wibull function