槭树科花粉形态及其系统学意义

报道了槭树科(Aceraceae)槭属21组33种和金钱槭属2种植物的花粉形态。本科花粉近球形至长球形，极面观为三裂圆形。从花粉萌发孔类型看，金钱槭属Dipteronia具三孔沟，槭属（Acer)除4组具三孔沟外，其余均为三沟。从花粉外壁纹饰看，金钱槭属2个种和槭属的大多数种为条纹状，罕为细条纹－拟网状和皱波状。通过花粉形态分析，并结合其它方向的证据，我们认为：（1）Sect.Palmata,Sect.Spicata和Sect.Microcarpa可能是槭属中与金钱槭属关系最密切的类群；（2）A.distalum和A.nipponicum代表了近缘的两个单种组；（3）A.pseudoplatanus不同于Sect.Acer的其它4个种而与A.saccharum可能存在更为密切的关系；（4）Sect.Carpinifolia(细条纹－拟网状外壁纹饰）和Sect.Negundo(皱波状外壁纹饰）则可能代表了槭属中最特化的类群；（5）按槭树科花粉三孔沟到三沟的演化规律，Dipteronia较Acer原始。

Pollen Morphology of Aceraceae and Its Systematic Implication

Pollen gains of 33 species in 21 sections of Acer,together with two species of Dipteronia were observed by light microscope(LM) and scanning electronic microscope (SEM). The shape of pollen grains in this family varies from subspheroidal to prolate in equatorial view and is 3-lobed circular in the poilar view. The aperture types of both species in Dipteronia are tricolporate. This type can also be found in 4 sections of Acer, but most species in Acer are tricolpate. As for the pollen exine sculpture, both species in Dipteronia and most spcies in Acer are striate, but two sections in Acer are finely striate-reticulatoid or regulate. By the studies of pollen morphology and other evidence, it is inferred that :(1)Sect.Palmata, Sect.Spicata and Sect.Microcarpa may be the closest groups in Acer to Dipteronia; (2) A. distalum and A. nipponicum represent two related monotypic sections; (3) The pollen of A. pseudoplatanus, which is different from other four species in Sect. Acer,is similar to that of A. saccharum. It therefore indicates that these two species have a close relationship; (4) Sect. Carpinifolia ,which has finely striate-reticulatoid exine sculpture, and Sect. Negundo, which has regulate exine sculpture, may be the most specialized sections in Acer; (5) Variation from tricolporate to tricolpate is regarded as an evolutionary trend in Aceraceae. The genus Dipteronia, therefore,is more primitive than the genus Acer.