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.