Abstract: Abstract The pollen morphology and ultrastructure of pollen wall of Pinus yunnanensis Franch. were examined with light microscope, scanning electron mi-croscope and transmission electron microscope. The pollen grains have sacci on both sides of body. The sacci are reticulate under LM and SEM. The exine surface contains tuberculate ornamentation under SEM. TEM examination reveals that the pollen wall from top to bottom includes sexine, nexine, incomplete outer intine, inner intine. Sexine is composed of tectum, baculum and foot layer. Nexine is homogeneous in structure and dark in colour. Exine and sacci are made of sporo-pollenin. The incomplete outer intine is composed of callose. The PAS action of the inner intine is positive. It is interesting to note that intine of the pollens kept for one year has changed in structure. Adhesion of the pollen mother cells, tetrad and pollen grains were described and analysed. The pollen morphology and size were various. Heteromorphic pollen grains without saccus, with one saccus, two abnormal sacci, three sacci and four sacci w.ere observed. These sacci are also reticulate under LM and SEM. The rate of the heteromorphic pollen grains is about five percent. The corpora of some heteromorphic pollen grains are larger than that of normal pollen grains. They are maybe polyploid. According to the observations, one of the reasons causing the heteromorphic pollen grains is probably the abnormal development and fusion of PMCs and tetrads.

Key words: Pinus yunnanensis

摘要： 在云南松(Pinus yunnanensis Fr．)小孢子发生发育过程中，花粉母细胞、四分孢子及花粉粒均见有粘连现象。花粉气囊的形态、大小变化复杂多样。除一般具两个正常气囊的花粉粒外，还观察到气囊不发育、具一个气囊、二个异形气囊、三个气囊和四个气囊的花粉粒。成熟花粉壁从外至内可分为外壁外层、外壁内层、内壁外层和内壁内层，它们的构成成分及形态均有明显差别。贮存后花粉的内壁结构发生了明显变化。

关键词: 云南松, 花粉形态, 超微结构