Comparative Study of the Pollen Wall Development in Illicium floridanum (Illiciaceae) and Schisandra chinensis (Schisandraceae)

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