Gametophyte Development and Antheridiogen Activity in Thelypteris ovata var. lindheimeri

Abstract

Gametophyte development was studied in Thelypteris ovata var. lindheimeri from spore germination to 48 days. Spores were sown aseptically onto the surface of agar-solidified mineral medium in multispore cultures. Germination began four days after spore sowing. Game- tophytes were spatulate in morphology at six days and terminal meristems were initiated at ten days. Antheridia were observed at 19 days, archegonia at 21 days. At 28 days, gametophytes were antheridiate (smaller, 0.6-1.0 mm in width), archegoniate (larger, 1.3-2.3 mm in width) or asexual (variable, 0.5-1.5 mm in width). Gametophytes remained unisexual at 48 days. The presence of an antheridiogen system was investigated using culture media extracts of T ovata gametophytes. Young gametophytes of T. ovata and Onoclea sensibilis L. form antheridia prematurely when exposed to partially purified culture media extracts. Two bands of biological activity were present after thin-layer chromatography, indicating the presence of at least two biologically active com- pounds. Studies of gametophyte growth and development play an important role in identifying new species of ferns with antheridiogen systems. Antheridiogens influence growth and development of gametophytes and their sexual mor- phology. They are synthesized by fern gametophytes and cause premature an- theridia formation in developing gametophytes. Antheridiogen systems have been described in several genera of ferns, including Anemia, Ceratopteris, Ly- godium, Onoclea, and Pteridium (reviews by Naf et al., 1975; Raghavan, 1989). In the schizaeaceous ferns, Anemia and Lygodium, antheridiogens also can substitute for the light requirement for spore germination. Morphological char- acteristics of fern gametophytes have been suggested to be of value in the classification of some fern groups (Stokey, 1951; Atkinson and Stokey, 1964). These morphological characteristics are obtained by studies involving growth and development of fern gametophytes from spore germination to reproductive maturity. Unfortunately, these studies are few considering the number of fern