واكنش فيزيولوژيكي گياهچه هاي گندم به دماهاي پايين

Physiological Responses of Wheat Seedlings to Low Temperatures

The aim of this study was to identify physiological traits related to low temperature resistance .Three wheat genotypes (Bezostaya, Boolani and Lines 18) differing in cold resistance were germinated and grown at 20 and 10 °C and were subjected to chilling (2 "C) and then freezing (-10 °C) stress at four- leaf stage. A split plot design with four replications in which growth temperature and genotypes were considered as main and sub plot. respectively. was employed. Measurements were taken before and after exposure to chilling and also after exposure to freezing. Plants germinated and grown at low temperature (10 "C) ( LT) showed higher soluble carbohydrate (SC) content and lower tissue water percentage (WP) at all measurement stages and higher chlorophyl (CHL) content only at prehardening measurement as compared to those grown at higher temperature(Con.)(20C). The highest SC and WP were observed in Bezostaya (resitant) and Line518 (sensitive), respectively. Exposure to chilling increased leaf SC and CHL contents of plants grown at both 10 "C and 20 C. Interaction effects between growth temperature and genotypes were observed For SC and CHL before and after exposure to chilling. It was also appeared that chilling induced increase in SC was more pronounced in plants grown at LT than those grown at Con. condition. Exposure to freezing, resulted in increased SC and decreasd leaf water potential, the highest reduction in WP and highest increase in SC being observed in Bezostaya. Damage to cell membrane, measured by solute leakage, due to freezing stress was greater in Line 518 than in Bezostaya. Traits measured in these experiments appeared to be correlated with cold resistance in the field condition.