Plant Science Division, Research School of Biology, The Centre for Advanced Microscopy, The Australian National University, Canberra, Australia.
Plant Cell Environ. 2010 Oct;33(10):1731-41. doi: 10.1111/j.1365-3040.2010.02178.x.
Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water-filled hydroid cells cavitated and were embolized at -4 °C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ∼ 20% of their original volume at a nadir temperature of -20 °C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20 °C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ∼-12 °C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20 °C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes.
使用冷冻扫描电子显微镜和能量色散 X 射线光谱技术，研究了苔藓 Ceratodon purpureus（Hedw.）Brid. 的基本结构和机械性能与耐冷冻温度的关系。与更复杂的植物不同，在冷冻过程中，苔藓内部没有积累冰。外部冰诱导干燥，其响应是细胞类型的函数；充满水的水螅细胞在-4°C时空化并栓塞，而内皮层的薄壁细胞发生细胞崩解，在最低温度-20°C时降至原始体积的约 20%。叶绿素荧光表明，这些冬季适应的苔藓在从-20°C 解冻后没有显示出损伤的迹象，而 GCMS 表明，糖浓度不足以赋予这种程度的耐冻性。此外，差示扫描量热法显示，在水合苔藓中内部冰核在约-12°C时形成，而干燥的苔藓在最低温度降至-20°C时没有显示出任何冻结的迹象。因此，苔藓的快速脱水为解决冻结问题提供了一个简洁的解决方案；去除冻结的部分。
