investigation of laboratory freeze tolerance of field grown fennel (fueniculum vulgar ) ecotypes

abstract in order to investigate the freezing tolerance of field grown fennel (fueniculum vulgare mill) under controlled conditions, a factorial experiment based on completely randomized design was conducted with three replications in agricultural college, ferdowsi university of mashhad in 2004. treatments were two fennel ecotypes (khorasan and kerman), two planting dates (oct 8th and 29th ) and six temperatures (0,-3,-6,-9,-12,-15°c). plants were harvested from the field on des 7th in controlled conditions exposed to the freezing temperature. plant survival percentage and re growth after 21 days under the greenhouse and plant necrosis degree after the six days under the lab condition were evaluated. greenhouse results showed that there wasn’t significantly different between khorasan and kerman ecotypes for survival percentage, height and number of nod but kerman ecotype had the higher leaf number than khorasan ecotypes. planting date had significantly effect on survival percentage, height, number of leaf, number of nod and percentage of plant dry weight. so 29 october planting date was higher than 8 october in the entire measured criteria. with lowering the temperature, survival percentage, height, number of leaf, number of node and dry weight had decreased trend. there was significantly different between planting dates on plant necrosis degree of plant in 6th day under the lab conditions. necrosis degree for 29 october and 8 october. planting date was 3.4 and 2.8% respectively. the highest necrosis degree was shown in -150c freezing treatment that it was twice than necrosis degree in 00c .