四种番荔枝科植物花粉形态

利用扫描和透射电子显微镜,观察了番荔枝科(Annonaceae)4属4种植物的花粉形态与结构.刺果番荔枝(Annona muricata)和金钩花(Pseuduvaria trimera)为四合花粉,有四角形、偏菱形、T-型、十字形和四面体形.前者花粉表面具小穿孔,后者为皱波状纹饰.蕉木(Oncodostigma hainanense)和那大紫玉盘(Uvaria macclurei)为单花粉,前者表面为皱波状纹饰,后者为粗褶皱状纹饰.透射电子显微镜下,蕉木和那大紫玉盘覆盖层较厚、连续.蕉木覆盖下层较薄,偶尔可见颗粒状物质或不规则小柱,为过渡型覆盖下层；那大紫玉盘覆盖下层颗粒状.基层分为内外两层,外层较厚,平或呈波浪状,内层具有2～4片层结构.在不同属或同属不同种之间,花粉特征差异较大,多样性非常丰富.金钩花具有四合花粉、覆盖下层小柱状等进化特征,同时又具有花粉粒小、覆盖层无穿孔等较原始特征.

Pollen Morphology of Four Selected Species in the Annonaceae

Pollen grains of four species representing four genera of Annonaceae were examined by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The pollen grains are tetrads in Annona muricata and Pseuduvaria trimera under SEM. The type of tetrad is various, being tetragonal, rhomboidal, T-shaped, decus- sate and tetrahedral. The sculpture of pollen in A. muricata is psilate and foveolate, but rugulate in P. trimera. The pollen grains are monad in Oncodostigma hainanense and Uvaria macclurei. In the former species, the ornamentation is rugulate, and in the latter it is coarsely folded. Under TEM, the rectum is thick and continuous in O. hainanense and U. macclurei. The materials from infratectal layer are less accumulated. There is an intermediate infratectal layer in O. hainanense, for some irregular columellae and sparse granules are both observed, but there is a granular infratec- tal layer in U. macclurei. Basal layer consists of an outer layer and a foliated inner layer. The outer layer is thick, and flat or tluctuant. The inner layer is composed of two to four foliations. The morphological differences are great among different genera or different species in the same genus, indicating a high diversity of pollen morphology in Annonaceae. There are both primitive and derived characters in O. hainanense or P. trimera. Such as in P. trimera, small size pollen grain and imperforate rectum are primitive characters, but tetrad and columellar infratecal layer are derived.