鹅掌楸属花粉的超微结构研究及系统学意义

POLLEN ULTRASTRUCTURE OF LIRIODENDRON AND ITS SYSTEMATIC SIGNIFICANCE

Exine sculpture of pollen grains is the distinctive and reliable character to classify the two species of Liriodendron L.i.e., L. chinense with foveolate-reticulate sculpture and L. tulipifera with rugulate-verrucate sculpture. According to the evolution of pollen sculpture, the foveolate?reticulate pollen of L. chinense is more primitive than the rugulate-verrucate pollen of L. tulipifera. Ultrastructure of pollen wall shows that the tectate-columellae pollen of Liriodendron is rarer structure type within Magnoliaceae and is more advanced than the atectate type and tectate-granular structural type of most taxa of Magnoliaceae. Palynology supports to treat the genus Liriodendron as a subfamily.