摘要
本文报道水杉(Metasequoia glyptostroboides Hu et Cheng)花粉外壁透射电镜资料,与杉科各属花粉特征做了比较。根据透射电镜观察表明,水杉花粉外壁由外壁外层和外壁内层组成。外壁外层由紧密联结的颗粒层和分布稀少的乌氏体组成。后者表面具小刺及不明显的纵向小沟。外壁内层具十分清楚的片层状结构,由10—15片组成。全部片层均具三层型结构,最外面(靠近外层)的几片,三层型结构特别清楚、明晰。有的三层型结构层中间的白线松散,形成三根极细的白线。
Metasequoia is endemic to China.Present study deals with ultrastructure of pollen exine of M.glyprostroboides Hu et Cheng,and in comparision with other genera of the family. Pollen grains of Metasequoia are spheroidal or subsphoroidal and 27.8(24.3—32.3)μm in dia- meter.There is a papilla in the distal face.The papilla is wide at the base,3.5—5.2 μm high, with pointed and circular end and the base crooked toward one s-ide.Exine is about 1.5 μm thick,layers distinct,Nexine is as thick as sexlne.Surface weakly granulate. According to observation by SEM,exine is cevered with fine granules and rather coarse tuberculae.The former can be easily separated from the latter.The loose and uneven tube- rculae are provided with minute spinules on the surface and generally fall off after acetolysis. The fine.and dense granulae,however,remain intact after acetolysis. The study by TEM shows that ektexine is made of granules densely arranged and connected, with each other.In addition,sparse Ubisch bodes are unevenly distributed on granular layer with gemmate surface.The thick endexine,is Composed of 10—15 lamellae.It is worthy to: note that all lamellae possess tripartite structure.But lamellae of endexine in other genera of Taxodiaceae have no tripartite structure except the lamella near ektexine.Number of lamella and thickness ot endexine in Metasequoia differ from those of other genera in Taxodiaceae; for example endexine with 8—10 lamellae in Taxodiurn,8—9 lamellae in Sequoia,6—7 lamel- lae in Glyptostrobus,6—8 lamellae in Cunningharnia,about 16 lamellae in Cryptomeria etc.
