physiological responses of different wheat genotypes to cold stress

in order to determine yield and physiological response of different wheat genotypes to low temperature, many pot and field experiments were conducted in 2007-2008 at the plant physiology laboratory, university of kurdistan, and ghamlo dryland agricultural research station in kurdistan province. in both experiments, the experimental design was a randomized complete block in a split plot arrangement with three replications. experiment was carried out in 2007. corresponding to three field sowing dates, oct 1th, oct 16th and nov 5th, three pot treatments were performed. pot treatments were conducted at following temperatures: 20 (control), 10 and 5 °c. temperature treatments were considered in main plot and twelve genotypes of dryland wheat were assigned to the sub-plots. both in pot and field experiments, leaf chlorophyll and sugar contents, fatty acids, polyamines and leaf water were significantly affected by treatments. when protein, spermine and oleic acid were measured, no differences were evident among genotypes. cold stress and genotype had significant effects on the lethal temperature 50 (lt50) and electrolyte leakage. among the genotypes, ogosta exhibited the highest cold resistance (lt50), and the lowest electrolyte leakage. also, sardari and ogosta had the greatest grain yield (1178-1210 kg.ha-1), chlorophyll a, chlorophyll b, soluble sugars, protein, putrescine, spermine, spermidine, linolenic acid and oleic acid.