Hardened and nonhardened whole plants of three potato species, Solanum tuberosum L., S. acaule Bitt., and S. commersonii Dun., and one interspecific cross, `Alaska Frostless' (S. tuberosum x S. acaule) were placed in a low-temperature chamber capable of maintaining -4 ± 0.5C for 6 or 12 hours. The chamber was designed to control the root temperature independently from the rest of the plant. Cold acclimation did not affect the ability of any of the potatoes tested to undercool (supercool). Solanum tuberosum and `Alaska Frostless' did not undercool for the times and temperatures tested and in all cases were killed. Whole plants of S. acaule and S. commersonii undercooled, in some cases, for up to 12 hours. When plants of S. acaule froze, they were severely injured, although their hardiness levels were reported to be lower than the temperature to which they were exposed in this study. Whenever leaves and stems of S. commersonii were frozen they were not injured. Once the soil was allowed to freeze, all plants, in all cases, were frozen.
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