我国西南地区独活属花粉形态及其系统学意义

POLIEN MORPHOLOGY OF THE GENUS HERACLEUM FROM SOUTH-WESTERN CHINA AND ITS SYSTEMATIC SIGNIFICANCE

我国西南的横断山区是独活属(Heracleum)在世界上的两个分布中心之一。本文对该地区16种具代表性独活属植物花粉进行了光学显微镜和扫描电镜观察。结果表明本属花粉为三棱长球形,超长球形或稀为椭圆球形;3孔沟,边孔;外壁2层,层次分明,基柱明显。根据花粉形态可归为:矩形、赤道收缩形二个花粉类型。其演化趋势为矩形型→赤道收缩型。花粉形态研究支持了O.Drude (1898)等关于独活属在伞形科中为一个自然的且较进化的类群的观点。本文从孢粉学角度对属下系统进行了讨论;结合花粉与外部形态分析,少管组应为该属较原始的类群,而与I.P.Mandenova(1951)将该组作为本属中较进化的类群的观点不一致。

The genus Heracleum (Umbelliferae) consists of over 70 species. So far, 26 species and 3 varieties of them are found in China; about 25 species and 1 variety distributed in Sorth -westen China. Hengduan Mountains is one of the another centers of distribution in the world. In the present paper, pollen morphology of 16 species of the genus Heracleum from this area was investigated. Pollen grains of all the species were examined by LM, SEM. Among them 14 species were palynologically reported here for the first time. The study showed that pollen grains of Heracleum in vary shape. Their framework was trigonal in solid form, tricolporate, pleurotreme and exine 2-lauered. The stratification of exine was clear and columellae usually were distinct. According to the characteristics of the pollen grains in Heracleum, it may be divided into clearly distinguished types: Rectangular type andEquatorially-constricted type. The evolutionary trends of pollen types were as follows: rectangular type→equtorial-constricted type. Pollen information supports that O. Drude (1898) etc. treated Heracleum as an advanced and nutural taxon in Umbelliferae. According to pollen information, Sect. Wendtia should be a comparatively primitive taxon, and Sect. Millefolia shorld be an advanced taxon in this genus.