Temperature affects germination indices of safflower (carthamus tinctorius l.)

Seed germination based on temperature experience extensive deviation and considered as one of the earliest phenotypic expressions of the plants. Accurate assessment of the germination time under prevailing thermic regulations leads to optimized plant populations. Studying genotypic differences and microclimate during the early life are key indicators for specie recruitment. The research was carried out to quantify the impact of different temperatures on safflower genotypes. The seeds of five safflower genotypes (PI-16308, PI-16309, PI-16315, PI-26744 and PI-26748) were tested for germination at six constant temperatures (10,15,20,25,30 and 35 degrees C). Individual and coupled response of genotypes and temperatures revealed significant variation for germination percentage and germination index. Thermal regulation of germination percentage, germination index, mean germination rate, mean germination time, coefficient of velocity of germination, coefficient of variation of germination time, uncertainty of germination process and synchronization index were found highly sensitive to different temperatures. The maximum efficiency of above indices was recorded at temperature range of 15-20 degrees C. Based on these results it is concluded that temperature range between 15-20 degrees C is best suited for safflower planting to get the optimum plant population.