effect of temperature on germination and cardinal temperatures for upper d and lower set up seeds of (rapistrum rugosum.)

in order to determine cardinal temperatures and some germination characteristics for type one seed (upper segment) and type two seed (lower segment) of rapistrum rugosum, an experiment was conducted on two type seed and10 levels of temperatures (3, 5, 10, 15, 20, 25, 30, 35, 40 and 45 °c) in completely randomized design with four replications in factorial experimental arrangement in weeds research laboratory, faculty of agriculture, ferdowsi university of mashhad in 2012. results indicated that the cardinal temperatures for type one seed (min, opt and max) were 0.7, 35.8 and 45.4c° and for type two seed were 1.3, 31.7 and 48.5, respectively. the highest germination percentage for type one seed (upper segment) was in temperature range 10-35°c and for type two (lower segment) was in 5-35°c. germination percentage in type two seed (81%) was more than type one (41%). there was significant different between length of plumule and radical of type one and two seed in 10°c (p≤0.05). as length of plumule and radical of type one was more than type two seed.