RESEARCHES CONCERNING THE IN VITRO DIFFERENTIATION OF THE FERN PHEGOPTERIS CONNECTILIS (MICHX.) WATT

Phegopteris connectilis is an apogamous species, endangered in certain regions. The ex situ conservation, through the in vitro production of the gametophyte, as well as the embryos and the plants, followed by their cryo-stocking, is necessary for ensuring the survival of the endangered species, while at pace with international methodology. The differentiation of the gametophyte is characteristic of the leptosporangiate ferns, passing through the following stages: prothallic filament, prothallic blade, cordate prothallus. The uni- or pluri-serial branchings formed on the gametophytes constitute the initial differentiation stage of a new prothallus. One-cell trichomes are differentiated on the gametophyte, which produce wax, protective against de-hydration. The in vitro culture has evinced the fast life cycle of this species, as the apogamous embryo is formed in the course of only seven weeks after culture inception. The first protophylles are formed out of the apogamous embryo and the initial stem cell is differentiated between the first two. In very few cases, however, it was noticed, at the base of the first leaf, the differentiation of the first root; the latter is formed at a stage when the young sporophyte already has two to three protophylles, as rhizogenesis is favoured by the addition of AIA and Kin in the medium. The plants thus obtained can be utilized for re-establishing the natural populations in the regions where the species is endangered.