evaluation the effect of temperature and photoperiod on growth and development periods of two canola cultivars

in order to study the effect of temperature and photoperiod (pp) on development rate of different vegetative and reproductive stages of canola, an experiment was conducted at agricultural research station of gonbad during 2005-2007. the experiment was a randomized complete block design arranged in a split-plot in two conditions, for example supplemental irrigation and rainfed. there were different regression equations between mean temperature and duration of development periods, i.e. a negative power equation for periods from planting to emergence and from emergence to beginning of budding, a quadratic equation for periods from beginning of budding to beginning of flowering and beginning of flowering to beginning of seed filling, and a negative linear equation for period from beginning of seed filling to physiological maturity. the decrease in seed filling period with increase in temperature was considerably higher in hyola401 hybrid than rgs003 cultivar, indicating that the response of hyola 401 development to temperature was more than rgs003. there was a positive linear relationship between mean pp from emergence to beginning of flowering with cumulative thermal time during this period, explaining 68 and 74 percent of the variation for hyola401 and rgs003 cultivars, respectively, showing the positive effect of pp on canola development from emergence to beginning of flowering. canola development was affected by pp and temperature during emergence to beginning of flowering, and temperature during beginning of flowering to physiological maturity.