凤仙花属总状花序组的花粉形态及其分类学意义

Taxonomic significance of the pollen morphology of sect. Racemosae (Impatiens)

关键词:  凤仙花科，凤仙花属，总状花序组，花粉形态，分类学，扫描电镜

Key words:  Balsaminaceae,Impatiens,sect. Racemosae,pollen morphology,systematics,SEM

摘要:

总状花序组隶属于凤仙花亚属凤仙花属，以具多花的总状花序、侧生萼片2枚、子房5室、果实为线状圆柱形、种子多数、迈卵形、种皮表面具指状突起等特征区别于该亚属的其他类群。前人对凤仙花花粉形态的研究表明凤仙花属的花粉形态对于属下分类及种间界定具有重要的分类学价值。而对于总状花序组来说，有关花粉形态方面的研究少有报道，为了进一步探讨该组花粉S的形态特征及其分类学意义，该研究应用扫描电镜技术对总状花序组的21种植物的花粉进行了观察。结果表明：总状花序组植物的花粉粒均具4条萌发沟，两侧对称，极面观为矩圆形、长矩圆形或近方形；长赤道面观多为椭圆形至矩圆形，短赤道面观为椭圆形；长、短赤道轴比值多在1.4~2.4范围内；表面具网状纹饰，网眼在花粉粒表面均匀分布或赤道面的网眼较极面观的小，网脊边缘光滑或具波状突起，网眼内具不同密度的颗粒状突起。该组的花粉形态与宏观形态性状相关性较小，但花粉极面观形状、长短赤道轴的比值、网眼的分布、网脊边缘形状、网眼内颗粒物密度等特征具有种水平上的稳定性和特异性，对该组植物种间界定具有重要的意义。

Abstract:

Section of Racemosae Hook. f. et Thomson, blonging to subg. Impatiens, Impatiens, Balsaminaceae, most of them distributed in South China and with a part of species radiated to southern slope of Himalaya and Europe. The species of this section are characterized by racemose inflorescences with many flowers, 2 lateral sepals, 5-carpellated ovary, linear capsule fruits with multiple seeds, subobovoid, and surface of seed with finger-like protuberance appendages, which well circumscribe this section from others of Impatiens. Pollen studies in previous works indicated that morphological characters of pollen grains were of valuable in subdivision of Impatiens and circumscription of Impatiens species. However, the species carried out pollen studies in sect. Racemosae are few concerned. In order to study the pollen grain characters and clarify their taxonomic significance of pollen morphology characters, 21 species from sect. Racemosae were sampled and investigated under Scanning Electron Microscope in this study. The observation results indicated that the species of sect. Racemosae were characteristic of 4-colpate pollen grain, zygomorphic, and oblong, long-oblong or sub-quadrate in polar view. The long equatorial view of pollen grain were elliptic to oblong, short equatorial view of pollen grains were elliptic; and the ratio of length of long equatorial axis to short one were mostly between 1.4-2.4. The exine of pollen grains were of reticulate ornamentation with lumina even in polar view or uneven equatorial view. The muri of lumen were smooth or sinuate towards margin. There were granules in the lumina with different densities. The pollen morphology characters of sect. Racemosae showed little correlation with the gross morphological characters within this section. However, variation in the aspects of pollen shapes in polar view, the ratio between long equatorial axis and short equatorial axis, distribution of lumen, muri of lumen smooth or sinuate and the density of granules in the lumina and so on, were consensus within species expressed the taxonomical value in circumscription of species within sect. Racemosae.