From Plant Press, Vol. 22, No. 2, April 2019.
This past fall members of the Department of Botany teamed up with Education & Outreach to hold an after-school class for 18 local teenagers called "Pterrific Pteridophyte Ptuesdays." Liz Zimmer, Peter Schafran, W. Carl Taylor, Gabe Johnson, Shruti Dube, Eric Schuettpelz, Steven Canty, Erika Gardner, and Juan Pablo Hurtado Padilla introduced students to collections-based research of plants over four consecutive Tuesdays in October and November. On the first night, the students received a tour of the US National Herbarium led by Gardner, which featured the fern collection and mounting rooms. Afterwards the students constructed growth chambers with aluminum foil and milk creates in which to incubate petri dishes of Ceratopteris spores that they learned to sow using aseptic technique.
Spores of Cyathea divergens and Cyathea myosuroides. Students learned to differentiate species based on spore ornamentation characters, such as differentiating perforate versus foveolate depressions. (photo by Juan Pablo Hurtado Padilla)
The following week, the students observed the germination of the gametophyte from the spore and then attended a special lecture by Schuettpelz on his career in pteridology and current research on the evolution of fern epiphytism.
The students spent the third class learning to identify potted fern specimens with a dichotomous key and then pressed frond specimens collected from the Smithsonian Gardens’ Urban Bird Habitat (west side of the museum). Students learned how to identify key morphological features of leaf dissection and indusia and sori. In addition to macromorphology, the students learned to describe a diversity of fern spores under light and electron microscopes. Padilla assisted the students in creating stunning 3D SEM images of spores that they used in a spore-based plant identification matching game.
Water was added to their sexually mature gametophyte cultures to precipitate the release of free-swimming sperm under the microscope. Students identified male and female gametangia and the spiral, multi-flagellated swimming patterns of sperm. With this knowledge of gametophyte fertilization, student groups then created an experiment where a serial dilutions of a pollutant, such as bleach, 409 degreaser, Ajax, or motor oil, were applied to a set of gametophyte cultures. The viability and fertilization rates of the cultures treated with various concentrations of pollution were then compared to that of control plates in which water was added to initiate fertilization. Apparently 409 spray does not kill C. richardii gametophytes, but has a relatively long-lasting inhibitory effect on fertilization. Overall, the students were very indusiastic to learn about ferns and were sori to say good-bye on the last night.
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