马先蒿属花冠无喙类的花器官发生

对花冠无喙类密穗马先蒿(Pedicularis densispica)和大王马先蒿(P．rex)的花器官电镜扫描发现，两种不同花冠型(无齿和具齿)的马先蒿花部器官发生和发育初期十分相似，表现为明显的单轴对称。2个萼片原基首先发生于花顶的近轴侧位，然后沿花顶边缘向远轴端发育形成--马蹄形结构。密穗马先蒿在近轴中部又出现1枚萼片原基，随后马蹄形结构分化出4枚萼片，并与近轴中部的原基愈合后构成5齿萼片；而大王马先蒿的2齿萼片直接由马蹄形结构发育而成。5枚独立的花瓣原基随后发生，但发育相对滞后；除近轴中部位置1枚空缺外，4枚雄蕊原基与花瓣原基位置呈交互发生；2个心皮原基同时在拱形花顶的近轴和远轴端发生，剩余的花顶形成中间的隔膜，并与2个心皮形成中轴胎座。对马先蒿与金鱼草(Antirrhinum majus)和毛地黄(Digitalis purpurea)花器官发生和发育初期的特征进行了比较，讨论了马先蒿属花冠对称性变化的意义。

Floral Organogenesis of Pedicularis (Orobanchaceae) with Erostrate Corolla

This paper presents the first report of floral organogenesis in Pedicularis Linn.(Orobanchaceae).Two species with erostrate corolla,P.densispica Franch.ex Maxim.(corolla with short tube,erostrate without teeth) and P.rex C.B.Clarke ex Maxim.(corolla with short tube,erostrate with teeth),were observed using scanning electron microscopy (SEM).They shared many similarities in floral organogenesis.The floral apex is subtended from the bract.A pair of sepal primordia is initiated from the lateral-adaxial floral apex,which forms a horseshoe-shaped meristem.A central-adaxial sepal primordium arises in P.densispica,and a fused horseshoe-shaped meristem develops four lobes sequentially.The central-adaxial sepal primordium and the horseshoe-shaped meristem fuse and develop into the 5-lobed sepals.In P.rex,the 2-lobed sepal develops from the horseshoe-shaped meristem directly.Initiation of the five petal primordia were observed only in P.densispica.In this species,two pairs of stamens arise alternate to the petal primordia,except the adaxial position,and their development is more rapid than that of the petals.Two carpels initiate simultaneously from a bulged floral apex abaxially and adaxially;the rest of this bulged apex contributes to the septum.The floral organogenesis of Pedicularis was compared with similar studies in Antirrhinum majus and Digitalis purpurea.Floral symmetry in Pedicularis and its significance were discussed.