اثر دماي پايين بر جوانه زني بذر و ويژگي هاي فيزيولوژيك گياهچه سه رقم گندم زمستانه

The effects of low temperature on seed germination and seedling physiological traits in three winter wheat cultivars

To understand some physiological aspects of low temperature tolerance in wheat, in two separate glasshouse experiments the effects of low temperature on seed germination (Exp. I) and seedling physiological traits (exp.II) in three wheat genotypes were studied. A split plot design with four replications in which different temperatures (5,10 and 20 C°, exp. I, and 10, and 20 C°, exp.II) and three genotypes (Bezostaya, Boolani, and line 518, with different degrees of cold resistance) were considered as main and sub plots respectively. Decline in temperature from 20 C° (control) to 10 and 5C° resulted in a significant increase in time to 50% germination and a significant reduction in coleoptile and radicle length, dry weight and water content. At lower temperature, dry weight and length of radicle and coleoptile were greater in Bezostaya than those in Boolani and Line5I8. In Bezostaya seedlings, soluble sugars and chlorophyll content were higher, while leaf and crown water content were lower compared to other genotypes. Decline in temperature caused a grater increase in crown sugar content of Bezostaya compared to the two genotypes and greater increase in chlorophyll a in Bezostaya and Boolani than in Line518. These results confirmed that trait such as those measured in this study, which may guaranty a rapid emergence and establishment of seedlings at low temperature and their survival at freezing temperatures, can be considered as parts of cold tolerance mechanisms and thus may be used in breeding programs for cold climates.