商陆属中五基数花起源于三基数花的新证据——非洲商陆的花器官发生

Pentamerous flowers in the genus Phytolacca have been derived from trimerous flowers-New evidence from the floral organogenesis of Phytolacca dodecandra

运用扫描电镜和石蜡切片方法对非洲商陆PhytolaccadodecandraL′Her.的花器官发生过程及花器官各部分的位置排列进行了观察。结果表明 :非洲商陆萼片 5枚 ,以螺旋向心方式发生 ;没有观察到花瓣原基的发生 ;雄蕊为螺旋离心方式发生 ,前 4枚雄蕊分 2对出现在对萼位置 ,但此后发生的雄蕊的发生顺序明显区别于其他种 ;心皮 4- 5枚 ,与内部雄蕊互生。本文探讨了时空因素对花器官发生的影响 ,基于对非洲商陆花器官发生的观察 ,否定了“商陆属源于二轮雄蕊样式”的假说 ,并为商陆属中“五基数花起源于三基数花”

The floral organogenesis of Phytolacca dodecandra L'Her. (Phytolaccaceae) has been observed under both scanning electron microscope (SEM) and light microscope. The primordia of the floral appendage are arranged according to a pentamerous pattern and acropetal succession. Five sepal primordia arise in a 2/5 sequence, and no petal primordia have been observed. The stamen primordia arise centrifugally. The first two pairs arise successively opposite sepal one and two. In the subsequent initiation of inner and outer stamens, P. dodecandra differs from other species in the genus Phytolacca. The four or five carpel primordia arise in rapid succession, usually equal in number and alternating with the inner stamens. The effects of temporal and spatial factors during the floral organogenesis of P. dodecandra are discussed. The data on the androecial ontogeny in P. dodecandra refute the existence of diplostemony in Phytolaccaceae, in which P. dodecandra occupies a pivotal systematic position. The androecial ontogeny in P. dodecandra supports the viewpoint that in the genus Phytolacca pentamerous flowers have been derived from trimerous flowers.