中国紫草科厚壳树亚科的花粉形态及其系统学意义

为探讨厚壳树亚科在紫草科中的系统位置，用扫描电子显微镜研究了国产厚壳树亚科Ehretioideae的厚壳树属Ehretia、轮冠木属Rotula和基及树属 Carmona 3属12种植物的花粉形态，其扫描电镜资料属首次报道。从本文并结合文献报道的双柱紫草属 Coldenia的花粉资料，可得知该亚科花粉为长球形 、近球形，稀球形,赤道部位具有不同程度的膨大；萌发孔类型为三孔沟和三拟假沟二者交替排列，稀具三孔；外壁表面具微弱的小穿孔，稀光滑或皱波状纹饰。厚壳树亚科Ehretioideae与破布木亚科

Pollen morphology of the subfamily Ehretioideae in the Boraginaceae from China and its systematic significance

Pollen morphology in ten species of Ehretia and each one species in Rotula and Carmona of the Ehretioideae, Boraginaceae, was observed under scanning electron microscope (SEM). Pollen grains are prolate or subspheroidal, rarely spheroidal, more or less enlarged in the equatorial region, elliptic to subrhombic in equatorial view, and hexalobate-circular or obtuse-triangular in polar view; the apertures are 3-colporate alternated with 3 pseudocolpoids, and rarely 3-porate; the exine is faintly microperforate, rugulate or psilate. The results show that the subfamily Ehretioideae is distinctly different from the subfamily Cordioideae in pollen morphological features, such as the pollen shape, the aperture number and type, and hence support the treatment of them as two independent subfamilies. Some pollen morphological features, such as the rather large size of pollen grains and the equatorial region not being constracted, suggest that both Ehretioideae and Cordioideae might be primitive groups in the Boraginaceae, although the pollen grains in Ehretioideae seem to be of a higher evolutionary level than those in Cordioideae as shown by their shape and aperture features, and thus indicate that the former subfamily might be more advanced than the latter. Pollen grains in the genus Rotula in Ehretioideae are 3-porate, implying the possible close relationship between Ehretioideae and Cordioideae.