evaluation of nacl salinity stress using three different laboratory methods

to investigate the effects of different salinity levels of nacl on germination of safflower (cv. esfahan 24) seeds under three different incubation methods, a factorial experiment was carried out based on a complete randomize design with three replications. salinity levels were 0, 5, 10, 15 and 20 dsm-1 (nacl) and incubation methods were sandwich method, and using petri dishes with open or closed doors. the results showed that among investigated traits, including germination percentage and rate, length, fresh and dry weight of root and shoot, salinity had the highest negative correlation with germination percentage. there was not a significant difference in germination percentage between 5 dsm-1 and control, but increasing salinity levels to 10, 15 and 20 dsm-1 led to 13, 23.50 and 39.74 % reduction in germination percentage, respectively, compared to control (p<0.01). root growth was more sensitive to salinity than shoot growth. the reason of increase in root and shoot lengths and fresh and dry weights in sandwich method compared to petri dishes with close and open doors was lack of limitation for seedling growth and higher germination rate. in higher salinity levels, root length reduction in petri dishes with open door was lower than petri dishes with close door. it seems that in closed petri dishes, increase of seedling respiration in response to osmotic potential limits seed germination and therefore this method is not appear a suitable method to study in vitro germination behavior of safflower in response to salinity.