We analysed gynostemium development and morphology of 13 species of Spiranthinae to understand the structure and homology of this organ. Flowers and flower buds in different developmental stages were examined with scanning electron and light microscopy. Gynostemium ontogeny is similar in the early stages among the analysed species, and most of the differences arose at later developmental stages. Gynostemium development starts with the appearance of the anther primordium, followed by the median carpel and finally by the lateral carpel apices. The last emerges as two congenitally united, crescent-shaped prominences located between the median carpel apex and the labellum, eventually forming a rim of tissue on the proximal margin of the stigma. The rim can be receptive or not. The base of the median carpel apex contributes mostly to the receptive stigmatic zone and its apical region develops into the viscidium. The entrance of the stylar canal is located between the two partially non-receptive lateral carpel apices and the receptive base of the median carpel apex, refuting the idea that in Sarcoglottis it is located above the stigmatic area. There are no staminodal primordia, and the membranaceous appendages at each side of the column apex represent extensions of the clinandrium margins.

中文翻译：

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Spiranthinae (Cranichideae, Orchidaceae) 亚族绞股蓝的结构和发育

我们分析了 13 种Spiranthinae 的绞股蓝发育和形态，以了解该器官的结构和同源性。用扫描电子显微镜和光学显微镜检查不同发育阶段的花和花蕾。Gynostemium个体发育在所分析物种的早期阶段相似，并且大部分差异出现在后期发育阶段。Gynostemium 的发育从花药原基的出现开始，然后是中间心皮，最后是外侧心皮顶端。最后一个出现为两个先天结合的新月形突起，位于中心皮顶点和唇缘之间，最终在柱头的近端边缘形成组织边缘。轮辋可以接受或不接受。中央心皮先端的基部主要用于接受柱头区，其顶端区域发展为内膜。花柱管的入口位于两个部分不接受的外侧心皮顶点和中间心皮顶点的接受基部之间，驳斥了在 Sarcoglottis 中它位于柱头区域上方的想法。无雄蕊原基，柱尖两侧的膜状附属物代表前缘的延伸。