北京7种鬼针草属植物果实微形态特征及其系统学意义

Fruit Micromorphological Features of Seven Species of Bidens L.in Beijing and Its Systematical Significance

采用扫描电镜方法对北京地区鬼针草属植物7个种的果实微形态特征进行了观察、比较。结果表明:(1)7种鬼针草属植物瘦果的果体形状、表面棱的数目、芒刺(冠毛)数目及其上倒刺数目和生长位置等特征可以作为鉴定各种的重要形态学依据。(2)根据果皮在扫描电镜下表面纹饰类型及表皮细胞形状等特征,可将7种鬼针草分为两类:一类果皮表面为典型的网纹纹饰,表皮细胞呈不规则多边形,细胞界限明显;另一类果皮表面为条状网纹或纵条纹纹饰,表皮细胞呈长圆形或长条形,细胞界限不明显。由于7个种的果皮表面纹饰有着明显的差异和各自的特点,并与根据叶形、地理分布及分子等证据得出的系统亲缘关系结果基本相符,表明这一特征可能具有一定的系统学意义。

In this paper,the micromorphological features of the fruits of seven species of Bidens L.in Beijing were examined and compared under scanning electronic microscope（SEM） for the first time.The results showed that：（1）the shape of achenes,the number of pericarp surface edge,the number of pappi,and the number and position of retrorsely barbed awns on pappi,can be used as important morphological characters for identifying the seven species of Bidens;（2）The seven species can be divided into two groups based on the sculpture patterns and cell shape of pericarp.One group is characterized by typical reticulate sculpture and irregularly polugonal cells with obvious boundary,and the other is characterized by lathlike reticulate or striped sculptures and long round or stripe cells with unobvious boundary.The relationship analysis between some species based on pericarp sculptures is almost consistent with the result from leaf characters,geographical distribution and molecular data,indicating that this micromorphological feature probably has certain systematical significance.