evaluation of freezing tolerance of english daisy (bellis perennis) under controlled conditions

abstract the aim of this experiment was the study of freezing tolerance of bellis perennis under controlled conditions and were arranged in a completely randomized design with three replications. plants after sowing and grow in the bed, at the middle of autumn (after hardening in natural conditions), in the 7-8 leaf stage put on the thermogradiant freezer with the 12 freezing temperatures (0,-2,-4,-6,-8,-10,-12,-14,-16,-18,-20,-22 oc). cell membrane stability was measured through electrolyte leakage (el) and survival percentage and regrowth of the plants after 3 weeks in cold frame were measured, by counting the number of plants and determining their proportional with the number of plants before freezing and measuring the dry matter, number of flowers and fully developed leaves. with decreasing the temperature el increased significantly (p<0.05) and reach to the maximum at -180c. survival percentage of plants did not affect until -16 but all the plants were died in other sever freezing. dry matter of the plants was significantly (p<0.05) decreased by lowering the temperature from -60c. lethal temperature 50 (lt50) of samples according to the el and survival were -15.2 and -17.0, respectively.