Effect of short and long terms cold acclimation on biochemical characteristics of spring and winter wheat (Triricum aestivum L.) cultivars

To evaluate the effect of short and long term cold acclimation on biochemical characteristics of spring and winter wheat (Triricum aestivum L.) cultivars، an experiment was conducted in completely randomized design with three replications in greenhouses of the University of Tehran in 2009. The quantity of some antioxidant enzymes، reducing sugars، chlorophyll and carotenoids contents in two wheat winter (Norstar) and spring (Koohdasht) cultivars were measured and recorded، when seedling were acclimated at 3°C for 0، 3، 6، 12، 24 hours and two weeks. Results of LT50 showed that only Norstar winter cultivar was able to tolerate 12°C after two weeks of cold acclimation. In most cases the activities of enzymes were increased during the short term and then decreased after long term of cold acclimation. The increase of enzymes in the initial phases of cold acclimation represented that reactive oxygen species were rapidly detoxified during the short term cold acclimation. Since chlorophylls are the source of production of reactive oxygen species، the decrease in chlorophyll content in Norstar showed that this attribute، during cold acclimation، can be involved in freezing tolerance. In conclusion، results of this experiment indicated that both short-and long-term cold acclimation are important، however some metabolites are effective during the short term while others are effective during long term.