Studies on ontogeny and reproductive behaviour of Lepisorus nudus (Hook.) Ching (Polypodiaceae)

In-vitro studies of the ontogeny and mating system of the gametophytes of Lepisorus nudus were carried out through multispore and isolate cultures lasting 23 weeks. Spore germination begins early, on day 5-6. Spore germination pattern was Vittaria type and the germination percentage reached 82.69% (± 3.20%). Filamentous gametophyte did not branch and never produce separate prothalli. Occasionally the branching and separate prothalli were produced from mature and cordate gametophytes. Prothallial development was Drynaria type (cordate gametophytes with notched apex) contrary to other known species of Lepisorus, where gametophyte development was Kaulinia type (strap gametophytes without apical notch). Gametophyte production in multispore cultures reached up-to 75.6% (± 18.85%). All isolates initially produced archegonia and antheridia only after a prolonged cessation of production in archegonia. In contrast, only 37.2% (±12.63%) of individuals in multispore culture exhibited the same pattern with 29.8% (±7.56%) developing as males that did not produce archegonia by the end of the study. Only 37.2% (±12.63%) of archegoniate gametophytes developed antheridia by the end of the study and only once archegonia had degenerated; i.e., a temporal gap existed in expression of female and male gametangia. In multispore culture, only 26.21% (±5.70%) sporophytes developed on 160th day by fusion of female and male gametes that were derived from matings between sib gametophytes. In contrast, isolated gametophytes did not produce sporophytes. In isolate gametophytes, mature archegonia could not take delivery of male gametangia because antheridia were produced sequentially. This study suggests that the sequential expression of gametangia and absence of the intragametophytic selfing may also be a possible cause of reproductive barriers. Lepisorus nudus promotes inter-gametophytic selfing as an adaptive mechanism for reproductive success in multispore culture. This study presents a detailed account on reproductive biology of the taxa whose population is decreasing at distressing rate.