Anatomical Features of the Tubercle and Young Sporophyte of the Annual Fern Anogramma chaerophylla Growing in the Punta Lara Natural Reserve (Buenos Aires, Argentina)

LUNA, M. L.; RAMOS GIACOSA, J. P.; YAÑEZ, A.; GIUDICE, G. E.

AMERICAN FERN JOURNAL

AMER FERN SOC INC

Año: 2017 vol. 106 p. 231 - 241

0002-8444

The fern genus Anogramma is characterized by the presence of annual sporophytesand tubercles that persist through dry periods. Tubercles may host embryos that develop whenclimatic conditions are more favorable. As information on the structure of the tubercle andsporophyte of Anogramma chaerophylla is incomplete, the objective of this work was to analyzeanatomical characteristics during development and deepen knowledge of the adaptive strategies ofthis species. Spores were grown in-vitro and different stages of tubercle development andembryonic sporophytes were fixed in FAA, embedded in Paraplast and analyzed using lightmicroscopy. Initially, the green gametophyte developed antheridia and archegonia in its thickenedportion, where later bisexual tubercles differentiated. Embryos developed only from the archegonialocated in the tubercles, with one embryo developing per tubercule. During sporophyte growth thereserves accumulated in the tubercle were consumed. Oversized cells were observed at thejunction between the green gametophyte and the tubercle, suggesting a possible role intranslocation of substances. The young sporophyte consisted of a short shoot and a prominentfoot. The placenta comprised the foot cells and the adjacent tubercle cells. The first leavesprotruded soon and developed early as photosynthetic organs. Sporophytes remained attached tothe tubercles until advanced stages of development. Vegetative propagation was documented insmaller tubercles that did not develop gametangia. Because few sporophytes were observed in vivo,it is likely that natural populations are maintained through vegetative propagation of thegametophyte until favorable conditions encourage development of sporophytes.