Reproductive Biology Research Of Sevearl Species In Adiantum

Adiantum is Pteridaceae plant, with more than 200 species. Distributed in cold temperate zone to tropics, most in South America. There are 34 species in China, including 16 endemic. The researches about Pteridaceae have developed to multidisciplinary studies. But the studies of Adiantum are mostly concentrated in phylogeny, physiology and biochemistry, and less in reproductive studies. In recent years, there are many new species and hybrids found in this genus, especially in once-pinnate Adiantum. At present, reproduction studies on once-pinnate Adiantum in China, only the gametophyte development of A. malesianum and spore morphology of several species have been reported. In this paper we selected once-pinnate Adiantum as research materials to analysis the phylogenetic study based on 5 plastid genes by Maximum parsimony(MP), Maximum likelihood(ML), and Bayesian inference(BI). On the basis of a clear genetic relationship between species, we studied the reproductive biology of this group, including spore morphology evolution, gametophyte development and mode of reproduction, by using scanning electron microscope, spore artificial propagation, flow cytometry and other methods. The results as follow:In once-pinnate Adiantum, A. capillus-junonis is the basal group. A. menglianense and A. philippense are separate species as sisters. A. soboliferum is closest to A. menglianense and A. philippense and more evolutive than them. A. zollingeri from Thailand is identified as a sister species to A. caudatum in China. Ser. Gravesiana is closest to A. edgewothii.Spores of Adiantum are trilete and radial symmetry. The spores’ ornamentation are complex and diverse, and formed by the perispore. Spore surfaces could be divided into five types based on the surface ornamentation: psilate, scabrate, granulate, verrucate, and tuberculate the ancestor of once-pinnate Adiantum spores was polymorphic and the most probable plesiomorphic ornamentation was the tuberculate ornamentation.In this study, we observed gametophyte development of 6 representative species include A. philippense, A. juxtapositum, A. caudatum, A. malesianum, A. sinicum and A. gravesii. The types of their spore germination are Vittaria-type, except A. malesianum belonging to Osmunda-type. The types of their gametophyte development are Adiantum-type, except A. philippense, because of its special development.A. philippense, A. juxtapositum and A. malesianum can be developed vegetative propagation under sterile culture. One gametophyte can grow out a dozen or more daughter prothalli, also with archegonia and antheridia. Daughter prothalli can continue to vegetative propagate. The daughter prothalli of A. juxtapositum and A. malesianum begin to grow out rhizoid in later development. Daughter prothalli can absciss without scathe form mother prothalli and independent survival. The gametophyte of A. philippense can develop cluster between protonema and prothallium. The vegetative propagation of gametophyte can be regarded as vivipary like sporophyte.A. philippense and A. caudatum are apogamous. Two kinds color scales mature before the first leaf. Outer reddish brown scales develop into base of the petiole scales. Inner green scales develop into the scales and hairs of petiole and blade. They two species not grow out rhizoid in early development. A. philippense have “shaft structure” occasionally without hairs besides the first leaf. The order of sporophyte development is scales, leaves, roots. To determine if species is apogamous, we should combine with morphology, spore numbers in per sporangium and cell ploidy.Reproduction biology research of Adiantum not only provides the necessary evidence for evolution of complex family and formation of hybrid species, but also can provide a theoretical basis and technical support for the conservation and breeding.