Lancelot plantain (Plantago lanceolata L.) is a perennial herb from Europe, temperate Asia and North Africa [1]. It has been used for various medicinal purposes for centuries in Europe [2] and only more recently as a forage plant [3]. In order to evaluating freezing tolerance of this species conducted one experiment in 2011-12 under controlled conditions. Five ecotypes of Lancelot plantain (Bojnord, Kalat, Mashhad, Ghayen and Birjand) after 3 mounts growth and hardening in natural environment exposed to 8 freezing temperatures (0, - 3, -6, -9, -12, -15, -18 and -21°C). Electrolyte leakage percentage (EL%) and lethal temperature for 50% of plants according to EL (LT50el) determined for assessing plasma membrane stability. Plant re-growth determined 4 weeks after freezing treatment based on survival percentage (SU%), lethal temperature 50 percentage according to survival (LT50su), number of leaf, leaf area, leaf dry weight and reduced dry matter temperature 50 (RDMT50). Results showed that Mashhad and Birjand ecotypes had the least and the most EL% respectively. At the case of LT50el, Mashhad ecotype was the most tolerant and Kalat and Birjand ecotypes were the most sensitive ecotypes. Mashhad ecotype had more SU% than other ecotypes. In addition LT50su in Mashhad ecotype was 5.3°C lower than Birjand ecotype. Kalat and Birjand ecotypes had the highest and the lowest leaf area respectively. Mashhad and Birjand ecotypes were produced the highest and the lowest number of leaf and leaf dry weight, respectively. RDMT50 for Bojnord ecotype is 3°C lower than Birjand ecotype. Pearson correlation coefficient of EL% with SU% and leaf dry weight of plants in recovery period was negative and significant (-0.702** and -0.537* respectively). In addition there was positive and significant correlation between LT50el and LT50su (0.526*) and RDMT50 was exhibited negative and significant correlation only with SU% (-0.529*). According to these findings, Mashhad, Bojnord and Ghayen ecotypes exhibit suitable freezing tolerance. However for better understanding of Lancelot plantain responses to freezing stress there is needed doing more studies under field and controlled conditions.

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