凤仙花属棒凤仙亚属(凤仙花科)植物花粉形态的分类学意义

Taxonomic significance of the pollen morphology of subg. Clavicarpa (Impatiens, Balsaminaceae)

关键词:  凤仙花科, 凤仙花属, 棒凤仙亚属, 花粉形态, 分类学, 扫描电镜

Key words:  Balsaminaceae, Impatiens, subg. Clavicarpa, pollen morphology, systematics, SEM

摘要:

棒凤仙亚属代表着凤仙花属最先分化出的一支,以多年生草本,多于5朵花的总状花序,侧生萼片4枚,3沟花粉,心皮四室且每室具1枚种子,果实棒锤状,种子椭圆形以及三沟花粉其极面观为三角形而区别于其它种类。该亚属主要分布于中国南部,少数种类辐射分布至华中和中南半岛地区。已有报道证实花粉的形态特征对凤仙花属植物的属下分类具有重要意义,但对棒凤仙亚属的种类少有涉及。为了进一步探讨该亚属花粉的形态特征及其分类学价值,该研究应用扫描电镜技术对国产棒凤仙亚属植物的14种以及凤仙花亚属的窄萼凤仙花的花粉进行了观察。结果表明:棒凤仙亚属的花粉以单粒存在,具3条萌发沟,辐射对称,极面观为三角形或三角状圆形,花粉粒外壁具均匀的网状纹饰,网脊平滑或具波状边缘,网眼中具不同密度的颗粒状突起。棒凤仙亚属的花粉形态与水角属的花粉形态相似,表现出了其原始性; 其花粉形态特征与花部形态性状等相关性差,对该亚属的组级分类意义较小,但对于该亚属的种间界定具有重要意义; 而其花粉的极面观形状、赤道面观形状以及网状纹饰等变异相对稳定,对于界定该亚属具有重要的分类学价值。

Abstract:

Subg. Clavicarpa, the earliest basal taxa of Impatiens, are characterized by perennial herb, more than 5-flowered racemose inflorescence, 4 lateral sepals, hammer-shaped capsule, 4-carpellated ovary with one seed per loculus and 3-colpated pollen grain with trianger polar view. The majority of the subgenus occurred in South China with a few outliers radiated to central China and Indo-China Peninsula. Previous studies indicated that the morphological characters of pollen were valuable in the subdivision of Impatiens but few species involved in subg. Clavicarpa. In this study, pollen grains of 14 species from subg. Clavicarpa were employed and investigated under scanning electron microscope aimed at elucidating their taxomonic value. The results showed that pollen grains of subg. Clavicarpa presented as 3-colpate single grain and triangular or triangular-subcircular in polar view. The exine of pollen was reticulate ornamentation and muri of reticulate ornamentation were smooth or sinuolate towards margin. There were granules in the lumina with different densities. The pollen characters of subg. Clavicarpa were similar to that of Hydrocera. Moreover, morphological traits of pollen were poor in variation pattern and also lack of correlation with gross morphological characters. Therefore, the pollen grain traits could provide limited value in the further division of subg. Clavicarpa but with valuable evidences in circumscription of species. While some characters of pollen grains, eg. triangle in polar view and three germinal apertures are diagnostic characters to circumscribe subg. Clavicarpa.