| Differential thermal analysis (DTA) associated with viability tests, electrolyte leakage (EL) and tetrazolium chloride (TTC), were conducted to determine cold hardiness of three pecan cultivars, 'Desirable' 'Jackson' and 'Owens.' Fatty acids were identified by gas chromatography (GC). Critical temperature was estimated from the point where 50% electrolyte leakage occurred by regression.; Seasonal changes of cold hardiness have been observed in December and January for all cultivars. Pecan started to acclimate in the second week of September and reached maximum hardiness in January. All cultivars lost hardiness or deacclimated in February.; The predominate fatty acids in pecan stems were palmatic (16:0), stearic (16:0), oleic (18:1), linolenic (18:2), and linolenic (18:3). Seasonal variations of fatty acid composition were found during acclimation and deacclimation. The level of unsaturated fatty acids increased in winter while saturated fatty acids decreased. The increase of linolenic acid during acclimation caused an increase in the ratio of unsaturated fatty acids. Alteration in the proportion of fatty acids during cold acclimation may be associated with an increase in freezing tolerance. Fluctuations in the ratio of monounsaturated acid may be due to changes in enzyme activity. |
