estimation of base temperature and the investigation of germination and field emergence trend of monogerm sugar beet under various temperatures

to determine suitable planting date and predicting emergence time in field conditions of iranian sugar beet cultivars we need some information including base temperature (t base) and heat units (hu). in this research germination tests were conducted on the seed of seven iranian monogerm sugar beet cultivars at various temperatures (3 to 36 ºc) with 3 ºc intervals. also field emergence was evaluated in two years (2003-2004) with two planting dates in each year. this study determined optimum temperature and tbase for germination and meangermination time (mgt) at various temperature in laboratory and also mean emergence time and hu requirement in each planting date under field condition. results showed that t base for germination in different cultivars is varied between 2 to 3 ºc  with mean 2.6 ºc. the maximum germination percentage was in temperature between 12 to 27 ºc, but optimum temperature for germination was 24 to 27 ºc that there was maximum rate of germination in this range of temperature. required hu was 51 ºcd for germination and 154 ºcd for emergence under field condition.