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

Ultrastructure and development during meiosis and the tetrad period of sporogenesis in the leptosporangiate fern Alsophila setosa (Cyatheaceae) compared with corresponding stages in Psilotum nudum (Psilotaceae)

The pre-meiotic, meiotic and tetrad stages of development in microsporangia of Alsophila setosa were studied with particular emphasis on the early establishment of patterning in the microspore wall and the subsequent development of the sporoderm. The data obtained were compared with corresponding ontogenetic stages of Psilotum nudum. Tapetal behaviour was also examined. During the tetrad period, only one layer, a thin undulating sheet, appeared alongside the plasma membrane of the tetraspores, and this was evidently formed on a pre-patterned structure - a fibrillar layer, corresponding to a kind of primexine matrix. The early free microspores had a wavy plasma membrane with a parallel, sinusoidal, thin initial sporoderm layer. The proximal apertural fold was observed to be an extended outgrowth of this initial spore envelope. Sporoderm ontogeny during the tetrad period in Alsophila and Psilotum show some common points, but also fundamental differences, mainly in the relative timing of events: in Alsophila the end of the tetrad period is the starting point for exospore development, whereas in Psilotum the exospore is already complete at this stage. Considerable differences were also observed in the tapetum of the two species.Fil: Gabarayeva, Nina I.. Russian Academy of Sciences; RusiaFil: Grigorjeva, Valentina V.. Russian Academy of Sciences; RusiaFil: Marquez, Gonzalo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata; Argentin

The Effect of 4-Methylmorpholine N-oxide Monohydrate (MMNO.H2O) on Pollen and Spore Exines

Seven species of Cyatheaceae are native to Taiwan. Sphaeropteris lepifera, Alsophila denticulata, A. metteniana, and A. podophylla produced 64 spores per sporangium, whereas A. loheri, A. spinulosa, and A. fenicis produced 16 spores per sporangium. Spore germination was Cyathea-type, except in A. denticulata and A. metteniana. In these two species, the rhizoid formation was delayed. Gametophytes of all seven species usually underwent Drynaria-type development, but a few gametophytes of all seven species exhibited Adiantum-type development. Multicellular, scale-like hairs on the dorsal and ventral surfaces of the midrib cushion increased in size and changed shape with age. These scale-like hairs distinguish Cyatheaceae gametophytes from the gametophytes of other fern families. The first three or four fronds of young sporophytes lacked midribs. Uniseriate to multiseriate and club-shaped pluricellular hairs were intermingled on the fronds of juvenile sporophytes of all six species of Alsophila. The lacking of club-shaped pluricellular hairs on Juvenile sporophytes of S. lepifera supports the taxonomic separation of Sphaeropteris from Alsophila. The presence of 16- and 64-spored sporangia suggests two evolutionary events within Alsophila