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The dispersal of diaspores is a key process for successful reproduction, survival and evolution of plants. To model the dispersal of biological propagules (e.g., spores, pollen) it is necessary to measure their terminal velocity (Vt) in air. In this study, we used a new method based on video image analysis to measure Vt of spores of seven fern taxa. The average Vt of fern spores was 7.0 cm s−1, but varied among species from 1.6 to 11.3 cm s−1. Similar values were reported previously for airborne particles of mosses and seed plants. Spores of Danaea nodosa and Lophosoria quadripinnata had a lower Vt than other spores of similar size, perhaps owing to their surface ornamentation that increases their drag coefficient, or an air cavity, which diminishes their density. The reliability of the video image analysis method used here on fern spores was verified by comparing observed and theoretically calculated Vt of glass beads of known diameter and density. This method also allows the observation of spore behavior (e.g., rotation) as they move through the air. Because the method is relatively easy and inexpensive, it can promote future aerobiological research on other biological airborne particles as well.
As part of a revision of Selaginella subg. Heterostachys in Central and South America, S. hyalogramma Valdespino is described as a new species and illustrated with a line drawing, as well as with scanning electron microscope (SEM) images of leaves, sporophylls, and megaspores. This new species is characterized by non-articulate stems, heteromorphic vegetative leaves with idioblasts on their upper and lower surfaces that are also present on sporophylls, as well as dorsiventral, resupinate strobili and a laminar flap on lower surfaces of dorsal sporophylls. These characters serve to compare it to morphologically similar taxa. In addition, the presence of stomata along basiscopic leaf margins and basiscopic submarginal short or tooth-like hairs on upper surfaces of lateral leaves of this species are reported and discussed. Finally, S. hyalogramma is only known from a single collection made in the State of Táchira, Venezuela, where it grows as an epipetric plant on mossy sandstone areas that may be severely deforested and, hence, it is tentatively considered Critically Endangered (CR) according to IUCN categories and criteria.
We describe, discuss, and illustrate four new species of the fern genus Adiantum (Pteridaceae): one from Guyana (A. cremersii Boudrie & J. Prado) and two from French Guiana (A. granvilleanum Boudrie & J. Prado and A. latipinnulum Boudrie & J. Prado), and A. rivularis Boudrie & J. Prado that occurs in Guyana and French Guiana. The typification and application of the name A. oyapokense Jenman are also discussed.
Resurrection plants of the Selaginellaceae are renowned for their ability to tolerate desiccation as well as the small size of their nuclear genomes. These traits position Selaginella as a promising model system to understand many aspects of plant evolution. However, there is not an established method for the laboratory cultivation of resurrection species of Selaginella. We explored methods of in vitro propagation for resurrection species of Selaginella and identified a set of successful techniques. Our in vitro propagation system included two main steps: surface-sterilized megaspores were cultured alone on C-Fern agar medium for three weeks, followed by the addition of surface-sterilized microspores to the germinated megaspore cultures for co-culture. Sporelings of Selaginella eremophila and S. rupincola were observed after 2–5 weeks of co-culture, and all sporelings survived. Our methods aim to further the interest and use of resurrection species of Selaginella for manipulative studies to better understand the biology of desiccation tolerance and their unique genome architecture.