宽叶泽苔草的花器官发生

通过扫描电镜观察了宽叶泽苔草Caldesia grandisSamuel.的花器官发生。宽叶泽苔草 的萼片3枚，逆时针螺旋向心发生 ；花瓣3枚，呈一轮近同时发生，未观察到花瓣_雄蕊复合原基；雄蕊、心皮原基皆轮状向心 发生，最先近同时发生的6枚原基全部发育成雄蕊，随后发生的6枚原基早期并无差别，在发 育过程中逐渐出现形态差异，直至其中1－4枚发育成心皮，其余的发育成雄蕊；而后的几轮 心皮原基，6枚一轮，陆续向心相间发生。本文揭示了3枚萼片螺旋状的发生方式，并推测这种螺旋方式是泽泻科植物进化过程中保留下来

Floral organogenesis of Caldesia grandis Samuel.(Alismataceae)

The floral organogenesis of Caldesia grandis Samuel. was observed under scanning electron microscope (SEM). The primordia of the floral appendage were arranged according to a trimerous plan and in acropetal succession. Three sepal primordia were first initiated in anti-clockwise direction spirally, and a whorl of three alternisepalous petal primordia arose nearly simultaneously after the initiation of sepal primordia. The petal and stamen primordia were initiated separately, and no petal-stamen complex was observed. The stamen and carpel primordia all arose in whorl. The first six stamens arose alternately with the petal primordia. There were six organogenetic sites alternating with, and above, the first six stamens. These sites might initiate either a stamen or a carpel primordium. The following whorls of carpel primordia arose above and alternately with the previous whorls, and six primordia were maintained in every whorl. The evolutionary significance of the spiral development of corolla and the phenomenon of stamens sharing one whorl with carpels are discussed.