DEVELOPMENTAL BASE TEMPERATURE IN DIFFERENT PHENOLOGICAL PHASES OF WHEAT (TRITICUM-AESTIVUM)

The linear relationship between temperature and development rate has been widely recognized and it has been suggested that thermal units (the summation of daily mean temperature above a base temperature) can predict the phenological development of a crop. The aim of this paper was to determine the base temperature for different phenological phases of wheat. Two mediterranean wheat cultivars and five sowing dates were used to obtain different mean temperatures during development and different developmental rates. The linear regression of development rate against mean temperatures for each period indicated that there were no unique base temperatures for all stages of the life span and values close to 4-degrees-C and to 9.5-degrees-C were found to be best fits for base temperatures before and after the terminal spikelet stage of both cultivars. A model to predict wheat development was validated with another data set, which included different wheat cultivars and sowing dates. Estimates of the error in developmental prediction by using a single base temperature of 0-degrees-C is discussed as a function of separate development stages.