木莲属(木兰科)5种植物的花粉形态

Pollen Morphology of Five Species of Manglietia (Magnoliaceae)

光学显微镜下观察的木莲属(Manglietia)5种植物的花粉形态相似。长赤道轴大于45μm,属于大的花粉。扫描电镜下观察,花粉外壁均为小穴状雕纹,但毛桃木莲(Manglietiamoto)和厚叶木莲(M.pachyphylla)略为粗糙。透射电镜下观察,5种植物花粉外壁均可分为覆盖层、柱状层和基层。覆盖层不连续,有小穿孔。在远极面萌发沟区域,外壁逐渐减薄,最后覆盖层和柱状层消失,仅残留基层。柱状层内空间较密实,内部空隙小,多由颗粒构成,处于小柱发育的初级阶段。孢粉学资料证明木莲属是木兰科最原始的类群。

Pollen morphology in five species of Manglietia is similar. Pollen grains are large with the longest axis more than 45μm. Foveolate sculpture is observed on exine surface in all the five species except Manglietiamoto and M. pachyphylla which have slightly coarse exine. The exine of all species can be distinguished by itstectum, baculum and foot-layer. The perforation in tectum is clear. The colpus membrane consists of a thin foot-layer and intine, while the sexine elements (tectum and baculum) are reduced gradually. Spherical granules are frequently observed in baculum with small intraexinous spaces, which is at initial developmental stage. This study supports that genus Manglietia is the most primitive group in Magnoliaceae.