Evaluation of freezing tolerance in lancelot plantain (Plantago lanceolata L.) by electrolytes leakage index

In order to evaluate cold tolerance of Lancelot Plantain plant a Factorial experiment based on completely randomized design with three replications was conducted under controlled conditions in faculty of agriculture، Ferdowsi University of Mashhad. Experimental factors include plantain ecotypes (Bojnord، Kalat، Mashhad، Ghayen and Birjand) and freezing temperatures (0، -3، -6، -9، -12، -15، -18 and -21°C). Plantain plants after 3 months growth and hardening in natural environment for applying of freezing temperatures were transferred to a Thermo gradient freezer on January20، 2012. In order to assess plasma membrane stability، electrolyte leakage percentage (EL %) and the lethal temperature 50% of plants according to the EL% (LT50el) was determined. Plant survival assessed four weeks after freezing treatment by measuring survival percentage and the lethal temperature 50% of plant according to the survival% (LT50su). Results showed that at the case of LT50el، Mashhad ecotype was the most tolerant and Kalat and Birjand ecotypes were the most sensitive ecotypes. Ecotype and temperature interactions had noticeable effects on EL and Survival percentage، so in -12 °C، Bojnord and Birjand ecotypes had the least and the most EL% respectively. In the same treatment Mashhad ecotype with 94. 4 % and Birjand ecotype with 25. 4% exhibited the most and the least survival percentage. The value of LT50su for Mashhad ecotype was 5. 3°C lower than Birjand ecotype. There was high and negative correlation between EL% and survival percentage (r=-0. 70**) in this survey. Moreover there was significant and positive correlation between LT50el and LT50su (r= 0. 53*). According to these findings، Mashhad and Bojnord ecotypes exhibited suitable freeze tolerance than Birjand ecotype.