眼子菜的花器官发生(英文)

Floral organogenesis of Potamogeton distinctus A.Benn.(Potamogetonaceae)

运用扫描电镜观察了眼子菜的花器官发生过程。结果表明 :花原基从花序轴的基部开始以三数交互轮状的方式发生 ,在花原基发生的早期具有明显的苞片原基形成。花器官是以向心的方式发生的 ,二枚侧方花被片原基首先形成 ,紧接着产生二枚中间花被片。四枚雄蕊分两轮分别在与侧方花被和中间花被相对的位置发生 ,四枚雄蕊原基在发生时均呈长条形。上述四轮花被和雄蕊虽然在时间上以二数轮状的方式发生 ,但在空间上花被片和雄蕊各自分别排成一轮。最后 ,二个心皮原基在花原基顶端略偏于一侧并与雄蕊相间的位置同时发生。有些花的二枚心皮原基发生后其中一枚很早即停止生长或仅有一枚心皮原基形成。本文结果支持了眼子菜属心皮数目逐渐向简化的方向演化的观点。在花原基早期发育的过程中苞片原基的存在表明眼子菜属植物成熟花中缺乏苞片是简化的结果。

The floral organogenesis of Potamogeton distinctus A. Benn. was observed under the scanning electron microscope (SEM). The floral buds are first initiated on the lower portion of inflorescence in alternating whorls of three. Each of the floral buds is subtended by a bract primordium during the early stages. The primordia of the floral appendages arise on the floral bud acropetally. Two lateral tepals are first initiated and then two median ones soon after. Stamens are normally initiated as elongate primordia opposite the tepals, with the two lateral stamens preceding the median ones. The two carpel primordia arise alternating with the stamens. In some flowers, one of the two gynoecial primordia becomes inactive soon after they are initiated, or only one carpel primordium is initiated. The present observation of the gynoecial development supports the viewpoint that the evolution of flower in Potamogeton involves a reduction in number of parts. The existence of bract primordium during the early stages in many species of Potamogeton indicates that the absence of bract in mature flowers should be the result of reduction.