Comparative Observation On Sexual Generation And Embryonic Development Of Sphaeropteris Brunoniana And Alsophila Costularis

The Cyatheaceae is the only woody fern in existence.It is extremely valuable.It is called the national treasure and is ranked as the two grade protected plant by the state.However,the related research in China is late,and only limited to the community,artificial propagation and cultivation,medicinal ingredients of Cyatheaceae.The observation of the morphological and structural processes of spore germination,gametophyte development,sexual organ differentiation and embryo formation can provide experimental basis for the study of the internal mechanism of sporogenesis and theoretical basis and technical support for the breeding of Cyatheaceae.In this paper,two representative species of two different genera in the ancient relict plant Cyatheaceae are selected as the research materials.Through aseptic culture and soil culture,the sexual generation and the embryo development different structural characteristics of the two species of Cyatheaceae were observed and compared.The continuous development of antheridium,archegonium and embryo was observed by paraffin section.At the same time,the cultivation conditions of two Cyatheaceae plants in the breeding process were explored.By comparing the reproductive development of the two genera of Cyatheaceae,we can understand the phylogenetic relationship of the two genera from the microcosmic point of view,and provide basic data for the study of reproductive biology of Cyatheaceae.In terms of sexual generation,the spores of Sphaeropteris brunoniana and Alsophila costularis are all tetrahedral and radiation symmetric,and the spores are brown in color.The prothallus special mother cells begin to germinate at the three cracks.At the same time,the germination time of Sphaeropteris brunoniana is shorter than that of Alsophila costularis.There are no trichomes in the development of both species of Cyatheaceae,which accords with the characteristics of primitive ferns.In the process of nutritive cell development,Alsophila costularis is more likely to develop into necrotic cells,so it is more difficult to cultivate Alsophila costularis,that is to say,the habitat of Alsophila costularis is more demanding.The mature gametophyte of both Cyatheaceae species can develop into two different forms,the typical heart-shaped gametophyte and barred gametophyte.The sexual organ of Sphaeropteris brunoniana and Alsophila costularis are basically the same.The antheridium,the male reproductive organ,is composed of the canopy cell,the ring cell and the basal cell from the top to the bottom.The development of spermatogonia originated from the surface of gametophyte,but the maturation time of antheridium of Sphaeropteris brunoniana was much shorter than that of Alsophila costularis.The female reproductive organs of two species of Cyatheaceae,archegonium,are similar in shape,size and development process.The growth site is just below the ventral side of gametophyte growth point.In the process of development,both horizontal and vertical divisions were carried out simultaneously.The embryo development process of Sphaeropteris brunoniana and Alsophila costularis is basically similar.The results of their developmental patterns showed that the first division of zygote was carried out along the X surface,forming two equal volume cells.The pattern of embryonic development can be determined as XZY-type,and there is no difference in the development process.Therefore,the characteristics in the process of embryo development can not be used as the basis for the classification of Sphaeropteris brunoniana and Alsophila costularis,but they are the same in the characteristics of embryo development of Cyatheaceae.In this study,it was found that both Sphaeropteris brunoniana and Alsophila costularis had higher requirements for growth environment,and the disease necrosis occurred during gametophyte development.In the experiment of sporophyte induction,it was found that the best medium of Sphaeropteris brunoniana and Alsophila costularis was 1/2MS and 10g/L sucrose medium,but the sporophyte transformation rate of Sphaeropteris brunoniana was significantly higher than that of Alsophila costularis.In the study of single factor control experiment on four environmental factors of temperature,light,pH and sowing density in the reproduction process of two kinds of Cyatheaceae plants,it was found that the most suitable conditions for the cultivation of Sphaeropteris brunoniana and Alsophila costularis were 25?,150?mol·m^-2·s^-1of light intensity and pH6.5.In the experiment of comparing the reproductive ability of Sphaeropteris brunoniana and Alsophila costularis under the most suitable growth conditions,it was found that the spore germination time,the appearance time of filaments,prothallial formation time and gametophyte formation time of Sphaeropteris brunoniana were earlier than that of Alsophila costularis.Finally,it takes about 40 days for Sphaeropteris brunoniana to form gametophyte,and about 50 days for Alsophila costularis.It can be determined that the reproductive capacity of Sphaeropteris brunoniana is stronger than that of Alsophila costularis.