中国紫草科天芥菜亚科花粉形态及其系统学意义

Pollen morphology of Heliotropioideae in Boraginaceae from China and its systematic significance

为了深入研究紫草科Boraginaceae的分类问题,用光学显微镜和扫描电子显微镜观察了中国紫草科天芥菜亚科Heliotropioideae天芥菜属Heliotropium 6种,砂引草属Messerschmidia 2种和紫丹属Tournefortia 1种植物的花粉形态。它们的花粉为长球形,赤道面观为椭圆形,极面观为六裂圆形或八裂圆形,少数为三角形。萌发孔有三种类型:(1)三孔沟与三假沟交替排列;(2)四孔沟和四假沟交替排列;(3)三孔沟。外壁表面具微弱的小穿孔,皱波状纹饰或表面近光滑。上述结果表明天芥菜亚科三个属之间有密切的亲缘关系。花粉特征表明紫丹属在天芥菜亚科中可能是比较原始的,天芥菜属的演化水平比紫丹属和砂引草属要高,而砂引草属介于其他两个属之间。花粉形态特征显示天芥菜亚科是厚壳树亚科Ehretioideae到紫草亚科Boraginaceae的过渡类型。紫丹属的花粉具三孔沟的萌发孔类型表明天芥菜亚科与破布木亚科Cordioideae有一定的亲缘关系。

In order to study the taxonomy of Boraginaceae further, pollen morphology of six species in Heliotropium, two species in Messerschmidia, and one species in Tournefortia from the subfamily Heliotropioideae was examined by light and scanning electron microscopy. Pollen grains are prolate. They are elliptic from the equatorial view, and 6-lobate circular, 8-lobate circular or rarely triangular from the polar view. There are three aperture types in the subfamily Heliotropioideae, namely： （1） 3-colporate alternated with 3-pseudocolpate type, （2） 4-colporate alternated with 4-pseudocolpate type, and （3） 3-colporate type. The exine surface is faintly perforated, rugous decorative, or rarely psilate. The results showed that the three genera in the subfamily Heliotropioideae of Boraginaceae are closely related. Based on pollen features, the genus Tournefortia might be basal in Helio- tropioideae of Boraginaceae. Heliotropium seems to represent a more derived lineage than both Tournefortia and Messerschmidia, and the genus Messerschmidia lies between Heliotropium and Tournefortia. Pollen morphological features suggested that the subfamily Heliotropioideae is a transitional type from Ehretioideae to Boraginoideae. Pollen grains in the genus Tournefortia of the Heliotropioideae are of 3-colporate aperture, implying a possible close relationship between Heliotropioideae and Cordioideae.