Structural and ultrastructural characterization of Selaginella lepidophylla, a desiccation-tolerant plant, during the rehydration process

Selaginella lepidophylla is a pteridophyte resurrection plant from Central America deserts that has been studied hitherto only for microphyll ultrastructure and photosynthetic activity during rehydration. With the present work the anatomy and cell ultrastructures have been examined during progressive rehydration. Light microscope observations clearly showed the maintenance in the dry condition of chloroplasts although in a crushed form, of chlorophyll content, and the restoration of the normal anatomical structures in stem and microphylls after the complete rehydration process. Electron microscope analyses permitted us to observe a gradual reorganization in the different cells of stem and microphylls of all the cytoplasmic components including the membrane systems present either in the protoplasm or in the organelles. In particular, the chloroplasts appeared to be able to newly accumulate starch, and then to recover the normal photosynthetic capacity. Therefore, it is possible to say that S. lepidophylla retains in the dry condition the cell structures in a well conserved state or, at least, in a functional state by protective mechanisms that permit a total reorganization of the cells after rehydration. This statement is further supported by the absence of any structural disruption effects in the rehydrated cells of S. lepidophylla.