为研究苜蓿属(Medicago L.)与胡卢巴属(Trigonella L.)间的亲缘关系,寻找两属间的分属依据,解决中间过渡类群的分类归属问题,对苜蓿属与胡卢巴属种类的种皮结构和花粉形态特征进行了观察和测量,并以苜蓿属和胡卢巴属植物的 40 个形态性状为依据、应用数量分类方法对供试的 16 个种类进行了聚类分析(UPGMA)和主成分分析(PCA)。 此外,还根据具有重要分类学意义的形态性状,编写了供试的苜蓿属和胡卢巴属 16 个种类的分类检索表。 观察结果表明,供试的两属植物(11 种)的种皮结构基本相同,均由栅栏组织细胞、厚壁细胞和薄壁细胞组成,但胡卢巴属种皮的帽状结构和栅栏组织的厚度均小于苜蓿属。 供试的两属植物(9 种)花粉形态特征相似,均为椭球形或近球形,赤道面观为椭圆形,极面观为三裂圆形;极轴和赤道轴长分别为 22. 67 ~ 34. 67 μm 和 17. 34 ~ 31. 60μm;花粉表面纹饰较简单,呈小穴状。 种皮结构和花粉特征显示两属的亲缘关系较近,仅种皮结构中的帽状结构差异具有一定的属间分类学意义。 聚类分析结果表明,在欧氏距离 10. 85 处,供试的苜蓿属(11 种)和胡卢巴属(5种)的 16 个种类被划分为 2 组,A 组均由胡卢巴属种类组成,B 组均由苜蓿属种类组成;在欧氏距离 9. 32 处,B 组可被进一步划分为 3 个亚组,所包含的种类分别为苜蓿属的阔荚亚属( Subgen. Platycarpos D. F. Cui)、镰荚亚属(Subgen. Medicago Tutin)和天蓝苜蓿亚属(Subgen. Lupulina Gressh.)的种类。 主成分分析结果表明,前 3 个主成分的累积贡献率较低,仅 57. 50% ;在前 3 个主成分中,果实和小叶的长宽比、花萼长和被毛状况、茎和小叶的被毛状况、小叶尖形状、花序长等相关性状的绝对权重值均在 0. 6 以上,具有重要的分类学意义;基于前 2 个主成分所做的二维散点图中供试的 16 个种类组成 4 个表征类群,与聚类分析结果一致。

In order to research the relationship between two genera of Medicago L. and Trigonella L., to find evidences for generic division and to solve the classification problem of transition taxa, testa structure characters and pollen morphological characters of two genera were observed and measured, and based on 40 morphological characters, cluster analysis ( UPGMA) and principal component analysis ( PCA) of sixteen species of two genera were conducted. Furthermore, the key to the sixteen species was compiled according to some morphological characters with important taxonomic significance. The observation results show that testa structure of two genera (11 species) is almost same, which is composed with palisade tissue, sclerenchymatous and parenchyma cells. But the thickness of cap-structure and palisade tissue of testa of Trigonella species is thinner than that of Medicago species. The pollen morphological characters of two genera (9 species) are similar and as follows: ellipsoidal or nearly spherical with elliptical in equatorial view and 3-lobed circular in polar view, the length of polar axis and equatorial axis is 22. 67- 34. 67 μm and 17. 34-31. 60 μm respectively and the ornamentation of pollen surface is relatively simple with little cave-shaped. The testa structure and pollen morphological characters indicate the close elationship between the two genera, but the difference of the cap-structure in testa between two genera has a certain taxonomic significance. The cluster analysis results show that sixteen species of Medicago (11 species) and Trigonella (5 species ) are divided into two groups at Euclidean distance of 10. 85, Group A consists of Trigonella species and Group B does of Medicago species. And Group B can be further divided into three sub-groups at Euclidean distance of 9. 32, which consists of three subgenus species belonging to Subgen. Platycarpos D. F. Cui, Subgen. Medicago Tutin and Subgen. Lupulina Gressh., respectively. The principal component analysis results show that the accumulated contribution rate of the first three principal components is lower with only 57. 50% . In the first three principal components, absolute weight values of length-width ratio of fruit and leaflet, length and hairy feature of calyx, the hairy feature of stem and leaflet, leaflet apex shape and inflorescence length are all more than 0. 6, showing that these characters have important taxonomic significance. In two-dimensional scatter diagram based on the first two principal components, sixteen species of the two genera are composed of four phenetic taxa, which are consistent with the cluster analysis result.