Exploring the High Variability of Vegetative Desiccation Tolerance in Pteridophytes

Abstract

In the context of plant evolution, pteridophytes, which is comprised of lycophytes and ferns, occupy an intermediate position between bryophytes and seed plants, sharing characteristics with both groups. Pteridophytes is a highly diverse group of plant species that occupy a wide range of habitats including ecosystems with extreme climatic conditions. There is a significant number of pteridophytes that can tolerate desiccation by temporarily arresting their metabolism in the dry state and reactivating it upon rehydration. Desiccation-tolerant pteridophytes exhibit a strategy that appears to be intermediate between the constitutive and inducible desiccation tolerance (DT) mechanisms observed in bryophytes and angiosperms, respectively. In this review, we first describe the incidence and anatomical diversity of desiccation-tolerant pteridophytes and discuss recent advances on the origin of DT in vascular plants. Then, we summarize the highly diverse adaptations and mechanisms exhibited by this group and describe how some of these plants could exhibit tolerance to multiple types of abiotic stress. Research on the evolution and regulation of DT in different lineages is crucial to understand how plants have adapted to extreme environments. Thus, in the current scenario of climate change, the knowledge of the whole landscape of DT strategies is of vital importance as a potential basis to improve plant abiotic stress tolerance.

Keywords: Selaginella; desiccation tolerance; ferns; protection mechanisms; pteridophytes.

Figure 1

Desiccation tolerance strategies exhibited by land plants. The most common and widespread strategies for vegetative desiccation tolerance (VDT) in the major groups of land plants are indicated. Some additional desiccation related characteristics such as natural rehydration and estimated incidence of VDT in each group are also described. Clades with desiccation-tolerant members are indicated in bold and asterisks.

Figure 2

Common habitats for desiccation-tolerant pteridophytes. Photograph of an ecosystem with rock formations in the national park Sierra de Órganos, Mex. (A), and a close-up of a representative community of desiccation-tolerant organisms (including several ferns and mosses, Selaginella sp., lichens) growing on a rock outcrop (B). Resurrection plants can occupy rock crevices and shallow depressions where they experience periodic dryness, which represent inadequate sites for the establishment of desiccation-sensitive plants. Examples of desiccation-tolerant pteridophytes growing at these types of sites: the fern Myriopteris aurea (C) and the lycophyte Selaginella pilifera (D). All photographs were taken during the rainy season.

Figure 3

Overview of the intermediate vegetative desiccation tolerance strategy exhibited by pteridophytes. Desiccation-tolerant pteridophyte species can display a dominant strategy that is either constitutive (orange) or inducible (blue). A summary of the main characteristics and responses associated with each strategy are indicated. Some additional factors that can regulate desiccation tolerance capacity are indicated by discontinuous lines.