野雉尾金粉蕨配子体发育及其系统学意义

野雉尾金粉蕨为中国蕨科金粉蕨属植物,而金粉蕨属的系统位置一直存在争议。该研究用原生境腐殖土和改良克诺普氏(Knop’s)营养液对野雉尾金粉蕨的孢子进行培养,培养条件为温度25℃、光照强度2 500 lx、光照12 h/d,在光学显微镜下观察记录其孢子萌发和配子体发育过程。结果表明:野雉尾金粉蕨的孢子为黄褐色,四面体型,三裂缝,赤道面观为扇形,具周壁,外壁表面具网状纹饰。孢子培养7 d后开始萌发,孢子萌发类型为书带蕨型(Vittaria-type)。孢子萌发后,配子体原始细胞经多次横向分裂形成3~9个细胞的丝状体,丝状体细胞呈圆筒形,壁薄,侧壁向外鼓起,含有颗粒较大且数量较多的叶绿体。15 d左右发育为片状体,片状体多为匙状。25 d左右形成幼原叶体,幼原叶体不对称,配子体发育类型为水蕨型(Ceratopteris-type)。在原叶体发育过程中分枝丝状体非常发达,配子体呈丛状生长,整个发育过程没有毛状体产生。野雉尾金粉蕨的假根为单细胞管状,偶有分支,内无叶绿体。45 d左右精子器开始出现,精子器顶面观近圆形,侧面观为近椭圆形或短柱状。精子器成熟时,盖细胞裂开,精子逸出。60 d左右颈卵器出现,颈卵器比较大,基部略大于顶部,侧面观呈烟囱状,顶面观为铜钱状,颈部由四列细胞构成。90 d左右发育出肉眼可见的幼孢子体。从研究结果看,其配子体发育的特征与凤尾蕨科(Pteridaceae)凤尾蕨属(Pteris L.)相似,支持金粉蕨属归于凤尾蕨科的观点。该研究结果为野雉尾金粉蕨系统学研究提供了配子体发育方面的证据。

Gametophyte development in Onychium japonicum and its systematic significance

Onychium japonicum falls into the category of Onychium Kaulf. of Sinopteridaceae;however, the alliance of Ony-chiumremains controversial. In this study, the spores of O. japonicum were artificially cultured in the original habitat humus soil and improved Knop′s nutrient solution in a constant temperature of 25℃ with 12 h of light and dark respectively per day and 2 500 lx of light intensity. Spore germination and gametophyte development were observed and recorded at every stage under the microscope. The results indicated that mature spores were tawny,tetrahedral,3-colporate,with fan-shaped e-quatorial view,perispore and reticulation on the surface of the exine. The germination procedure was Vittaria-type while the gametophyte development was Ceratopteris-type. The spores cultivated in either of the two substrates began to germinate a-bout 7 d and their germination shared the same Vittaria-type. With multiple transverse fission,the original gametophyte cell gradually turned into 3-9 protonemata with cylindrical shape, thin perispore,lumpy lateral exine and numerous granular chloroplasts. After about 15 d,the spores developed into prothallial plates and most of prothallial plates appeare spatulate.And 25 d later, young prothalliums were formed but they were not symmetrical;meanwhile, the gametophytes developed were Ceratopteris-type. When the prothalliums were developing, branching protonemata were flourishing and gametophytes were becoming fasciculate without any trichome. The rhizoids of O. japonicum, occasionally branching and lacking chloro-plasts, were unicellular and tubular. After about 45 d,antheridium, composed of a cap cell, a ring cell and a basal cell, e-merged from the edge of several irregular prothalliums. When the antheridium became mature, the cap cell split and sperm spilt. The antheridium looked like a circle from the top and an oval or a short column from the side. About 60 d later, a large archegonium was clearly visible. Its base was bigger than the top. It looked like a coin from the top and a chimney from the side. Its neck consisted of four rows of cells. When the archegonium was fully developed, sperm entered and fertilized the egg cell inside. Half a month later, a young embryo could be clearly seen. About 90 d after sowing,the spores developed into juvenile sporophytes which were visible to the naked eye. It could be concluded from the findings that O. japonicum shared similar characteristics with Pteris of Pteridaceae in terms of gametophyte development. Therefore, O. japonicum could be classified into the Pteridaceae family. The study would provide evidence for the phylogenetic study of O. japonicum from the perspective of gametophyte development.