Malek L, Bewley J D
Department of Biology, University of Calgary, Alberta, Canada T2N 1N4.
Plant Physiol. 1978 Mar;61(3):334-8. doi: 10.1104/pp.61.3.334.
The response of the drought-tolerant moss Tortula ruralis ([Hedw.] Gaertn., Meyer, Scherb.) to freezing and thawing at controlled rates has been studied. Slow freezing (at 3 C per hour to -30 C) of hydrated T. ruralis leads to only temporary, reversible changes in metabolism. These changes can be considered to result from desiccation due to extracellular ice formation. In contrast, rapid freezing in liquid N(2) and thawing in 20 C water leads to deterioration in all aspects of metabolism studied: ribosome, protein, and ATP levels decrease, and in vivo and in vitro protein synthetic activity is lost rapidly. Such changes probably result from intracellular ice formation. Following freezing and thawing at an intermediate rate (60 C per hour), only ATP levels and in vivo protein synthesis are reduced. The protein-synthesizing apparatus (the polyribosomes) remains intact and active in an in vitro protein-synthesizing system even 24 hours after one 60 C per hour freeze-thaw cycle. These metabolic responses are discussed in terms of the two-factor hypothesis of Mazur et al. (1972 Exp. Cell Res. 71: 345-355).
已对耐旱藓类植物扭口藓（[ Hedw.] Gaertn., Meyer, Scherb.）在可控速率下的冻融反应进行了研究。对含水的扭口藓进行缓慢冷冻（每小时3℃至-30℃）只会导致新陈代谢出现暂时的、可逆的变化。这些变化可被认为是细胞外结冰导致脱水的结果。相比之下，在液氮中快速冷冻并在20℃水中解冻会导致所研究的新陈代谢各个方面恶化：核糖体、蛋白质和ATP水平下降，体内和体外蛋白质合成活性迅速丧失。此类变化可能是细胞内结冰所致。以中等速率（每小时60℃）进行冻融后，只有ATP水平和体内蛋白质合成会降低。即使在每小时60℃的冻融循环一次24小时后，蛋白质合成装置（多核糖体）在体外蛋白质合成系统中仍保持完整且活跃。根据Mazur等人（1972年，《实验细胞研究》71: 345 - 355）的双因素假说对这些代谢反应进行了讨论。
