Increase in linolenic Acid is not a prerequisite for development of freezing tolerance in wheat.

Seedlings of winter wheat (Triticum aestivum L. cv. Kharkov) were acclimated at 2 C in the dark in the presence of two inhibitors of linolenic acid synthesis, 4-chloro-5(dimethylamino)-2-phenyl-3(2H)pyridazinone-(BASF 13-338) and 4-chloro-5(dimethylamino)-2-(alpha,alpha,alpha-trifluoro-m-tolyl)- 3(2H)pyridazinone (Sandoz 6706). Although the increase in the proportion of linolenic acid generally observed at low temperature was completely inhibited, the development of freezing tolerance was unaffected. These results demonstrated that an enrichment in linolenic acid is not a prerequisite for low temperature acclimation.

Relative insensitivity of mitochondria in hardened and nonhardened rye coleoptile cells to freezing in situ.

Mitochondria were isolated from excised coleoptiles of hardened and nonhardened winter rye (Secale cereale L. cv. Puma) seedlings which had been frozen extracellularly to different temperatures. No significant differences in the respiratory functions (ADP/O and respiratory control) were observed between mitochondria isolated from nonlethally and lethally frozen cells of both the hardened and nonhardened rye. These results suggest that mitochondria in situ can retain their normal function even after the cell was killed by the dehydrative stresses of extracellular freezing. Presumably, a different level of sensitivity to freezing stresses exists between mitochondrial and other membranous elements in the cell.