Abstract The desiccation tolerant (DT) fern species Crepidomanes inopinatum and Loxogramme abyssinica often grow together in the understory of KwaZulu-Natal Afromontane forests. Crepidomanes inopinatum is a “filmy” fern that dries rapidly because it lacks a cuticle; by contrast L. abyssinica possesses a cuticle, and therefore dries slowly. It was predicted that because C. inopinatum dries quickly, this species would have little time available to induce DT mechanisms, and therefore mainly relies on constitutive mechanisms. By comparison, the slow-drying L. abyssinica has time to put DT mechanism in place, and therefore may depend more on inducible mechanisms. Here we tested whether a drying-rehydration cycle induces two mechanisms often suggested to contribute DT, specifically increases in the activity of two reactive oxygen species (ROS) scavenging enzymes and the concentration of soluble sugars. Measurement of chlorophyll fluorescence parameters showed that both species recover rapidly during rehydration after desiccation, confirming that both are genuinely poikilohydric. In both species slow desiccation increased the activity of the ROS scavenging enzyme superoxide dismutase (SOD), and the concentrations of soluble sugars. Desiccation had little effect on the activity of the (ROS) scavenging enzyme peroxidases (POX) in either species, suggesting that maintenance of POX activity is a constitutive DT mechanism. However, the main difference between the two species was that de-acclimation occurred in the filmy fern; moist storage under cool dim light for a week reduced DT. By contrast, in the fern with a cuticle no de-acclimation occurred. However, overall, results suggest that counter to our original hypothesis, inducible DT mechanisms occur even in filmy ferns that desiccate rapidly.

中文翻译：

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干燥耐受机制的诱导发生在快干薄膜蕨类植物 Crepidomanes inopinatum 和慢干蕨类植物 Loxogramme abyssinica 中

摘要 耐旱(DT) 蕨类植物Crepidomanes inopinatum 和Loxogramme abyssinica 经常一起生长在夸祖鲁-纳塔尔非洲山地森林的林下。Crepidomanes inopinatum 是一种“薄膜”蕨类植物，由于缺乏角质层，因此会迅速干燥；相比之下，L. abyssinica 具有角质层，因此干燥缓慢。据预测，由于 C. inopinatum 干燥快，该物种几乎没有时间诱导 DT 机制，因此主要依赖于组成机制。相比之下，慢干 L. abyssinica 有时间将 DT 机制落实到位，因此可能更多地依赖于诱导机制。在这里，我们测试了干燥-再水化循环是否会诱导两种通常被认为有助于 DT 的机制，特别是增加了两种活性氧 (ROS) 清除酶的活性和可溶性糖的浓度。叶绿素荧光参数的测量表明，这两个物种在干燥后的再水化过程中迅速恢复，证实两者都是真正的变水体。在这两个物种中，缓慢干燥都增加了 ROS 清除酶超氧化物歧化酶 (SOD) 的活性和可溶性糖的浓度。干燥对任一物种中 (ROS) 清除酶过氧化物酶 (POX) 的活性几乎没有影响，这表明维持 POX 活性是一种组成型 DT 机制。然而，这两个物种之间的主要区别是在薄膜蕨类植物中发生了去驯化；在凉爽昏暗的光线下潮湿储存一周会降低 DT。相比之下，在带有角质层的蕨类植物中没有发生去驯化。然而，总的来说，结果表明，与我们最初的假设相反，即使在迅速干燥的薄膜蕨类植物中也会发生诱导型 DT 机制。