Abstract

Pollen wall development of Illicium floridanum and Schisandra chinensis have been studied and compared. Both species have a similar reticulate exine, but their similarity occurred to be only superficial. At early tetrad stage of both species the plasma membrane acquires a regularly invaginative profile, the distribution pattern of invaginations on the microspore surface corresponds to the future reticulate exine pattern. In the invaginative sites of the plasma membrane of both species fibrillar strands appear which are the auxiliary (phantom) structures. Further developmental process is different in both species. In Illicium sporopollenin accumulates around the auxiliary strands, localized in plasma membrane invaginations, resulting in the appearance of the reticulate sculpture of hollow tunnels on the surface of a microspore; this reticulate pattern becomes concave after lifting of the invaginated portions of the plasma membrane. In Schisandra, on the contrary, sporopollenin never accumulates in the location of the auxiliary fibrillar strands (these are sites of future lumina), but sporopollenin accumulations concentrate on the elements of the glycocalyx on the evaginated top (protruding sites) of plasma membrane. The latter are sites for columellae formation, and muri are constructed from the rows of columallae covered by tectum. Hence, the development of the exine in both species is different, and the inner structure of reticulate exine in Illicium differs from that of Schisandra - in spite of the very similar sculpture.

中文摘要

多花八角(Illicium floridanum) 與中華五味子(Schisandra chinensis) 花粉壁的發育過程在本文中加以研究並比較。兩種植物花粉都具有相似的網紋外壁，但它們的相似處 僅在表面。在小孢子發育過程中四分小孢子時期的早期，原生質膜上都有一種具規則性凹陷的外表輪廓，這個表面凹陷的分佈型態與未來的花粉網紋外壁形態具一致性。而兩種植物的小孢子在原生質膜凹陷的位置內都會出現一種備用的(幻像般) 纖維束構造，但在花粉外壁進一步的發育過程中逐漸出現了差異。多花八角花藥中孢粉素會圍繞著原生質膜凹陷處的纖維束沈積，導致小孢子表面形成中空隧道般的網紋雕刻，這種網紋形態在原生質膜凹陷部分隆起後卻變成凹陷狀。相反的，在中華五味子花藥中孢粉素不曾堆積在纖維束周圍(這個位置將會形成未來的網目中)，堆積卻集中在原生質膜上臘梅糖所形成的凸起頂端(突起的位置上)。後者為圓柱體形成的位置，由於多列的圓柱體會被蓋頂層所覆蓋，而形成了網格。雖然多花八角與中華五味子具有相似的網紋外壁，但內部結構卻有差異，因此可見兩種植物的花粉外壁發育過程是不盡相同的。

Keyword: Exine patterns, Auxiliary structures, Illicium floridanum, Schisandra chinensis