Developmental Characteristics Of Gametophytes In Some Species Of Cheilanthoid Ferns And Their Systematic Implications

Cheilanthoid ferns are a complex fern group in family relationship, the taxonomy problem were puzzling botanists in long term. Recently, molecular studies had great influence on its taxonomy system, but still need more evidences. Gametophyte period are playing great roles in fern’s life, and its feature will provide important evidence to its taxonomy studies. But there is little study about the Chinese cheilanthoid ferns.In order to understand the phylogenetic significance of farina in gametophytes of fern, the gametophyte development of 9 species of cheilanthoid ferns:Aleuritopteris anceps、A. argentea、A. ageantea var. obscura、A. squamosa、A. kuhnii (Leptolepidium kuhnii)、Gymnopteris marantae、 G. vestita、Pellaea connectens and Cheilanthes nudiuscula(Notholaena hirsuta) and 3 relative species Cryptogramma raddeana、Coniogramme merrillii and Onychium japonicum were observed. The process on shape, hairs, sexual organ, excretion, and embryo were carefully studied. This study aims to solve the phylogeny of Chinese cheilanthoid ferns. It will provide important scientific basis for the phylogeny studies on this fern group. At the same time, the research is also helpful to our comprehension of their adaptive evolution.Conclusion:1. The gametophyte development and the characters of young sporophyte of Aleuritopteris, Leptolepidium, and Gymnopteris have no significant differences, but the characters of young sporophyte of Coniogramme merrillii, Cryptogramma raddeana, and Onychium japonicum are different from the above cheilanthoid ferns, supporting the taxonomy of separating them from Cheilanthoids.2. The farina on gametophyte of Aleuritopteris squamosa, supporting the opinion of this gametophytic character is not a synapomorphy for the notholaenoids. As the farinose gametophyte now observed in two of the four clades of cheilanthoid ferns, it was postulated that the farinose gametophyte would be derived independently at least twice in the evolution of the cheilanthoid ferns. The fact that the farina is produced exclusively in female gametophytes implies that the occurring of the farina would be relevant to the gender differentiation and the embryo formation in cheilanthoid ferns.3. Cheilanthes nudiuscula (Notholaena hirsuta), which is a strict apogamy species, is greatly different from other Chinese cheilanthoid ferns. The special species may represent a different line of evolution.