studying the effect of drought and freezing on tuberous root germination of lesser cleandine ( ranunculus ficaria)

abstract r. ficaria is an invasive perennial and tuberous roots weed. the most important means of its reproduction and dispersion are tubers. in order to study the effect of droughty and freezing on germination of lesser celandine tubers, two experiments were conducted at weed science laboratory of faculty of agriculture ferdowsi university of mashhad in 2008. the experiment was a completely randomized design with factorial arrangement of treatments and four replications. in freezing experiment, factors included of time of exposure to freezing(12,24,48 and 96 hours) and freezing temperature (0,-5,-10 and -15 ˚c). to examine the effect of desiccation on ficaria tubers, factors included of , five levels of temperature(5,10,15,20, and 25 ˚c), four levels of osmotic potential(0,-5,-10 and -15 bar) and two tuber sizes [big(>0.2g) and small(<0.05g)]. in freezing experiment factors and their interactions had significant effect on germination of tubers. decreasing the temperatures and increasing the storage time in freezing experiment, decreased the germination of tubers. germination not occurred in tubers which had been stored at -10˚c and -15˚c for beyound 48 hours. results showed that drought stress had significant effect on germination of tubers. increasing the osmotic potential and temperature decreased the germination of ficaria tubers. in osmotic potential -15 bar, germination was zero in all of temperatures. no significant difference was observed among big and small tubers. in all temperature, osmotic potential and tubers size decreasing the tuber weight were significant. keyword: ranunculus ficaria, germination, tuberous root, freezing, drought