Abstract
Palynology of six fern species belonging to the family Aspleniaceae from Saudi Arabia are investigated by light microscope (LM). These are: Asplenium aethiopicum, Asplenium trichomanes, Asplenium adiantum-nigrum, Asplenium sp.1, Asplenium sp.2 and Ceterach officinarum. All studied spores are oblate-spheroidal in shape class, with 11 - 50 μm in equatorial diameter and with 12 - 49 μm in polar diameter. Two types of spores are recognized: monolete spores in Asplenium aethiopicum, Asplenium trichomanes, Asplenium adiantum-nigrum, Asplenium sp.2 and trilete spores in Asplenium sp.1 and Ceterach officinarum. The exospore (perine) is homogeneous and apparently double-layered in all the studied spores. The perispore is single or double-layered with a microlacunouse structure. The perispore layers can be distinguished by their different contrast, structure and thickness. The exospore sculpture varies from cristates-ridged (Asplenium aethiopicum), cristates granulate (Asplenium adiantum-nigrum), cristates scabrate (Asplenium trichomanes), regulate-scabrates (Asplenium sp.1 and Ceterach officinarum) to papillate or tuberculate sculpture (Asplenium sp.2). Comparison between the earlier studies of some species from Saudi Arabia is given. General characteristics like spore type, ornamentation and laesurae features as well as the number of exospore layers could be useful for taxonomy of Aspleniaceae.
Highlights
The Aspleniaceae is a family of ferns, included in the order Polypodiales or in some classifications as the only family in the order Aspleniales
Palynology of six fern species belonging to the family Aspleniaceae from Saudi Arabia are investigated by light microscope (LM)
General characteristics like spore type, ornamentation and laesurae features as well as the number of exospore layers could be useful for taxonomy of Aspleniaceae
Summary
The Aspleniaceae (spleenworts) is a family of ferns, included in the order Polypodiales or in some classifications as the only family in the order Aspleniales. Many groups of species have been separated from Asplenium as segregate genera These include Ceterach, Phyllitis, and Tarachia, but these species can form hybrids with other Asplenium species and because of this are usually included in a more broadly defined Asplenium [4,5]. Asplenium is one of the largest fern genera, of about 700 species, distributed worldwide from Greenland and Europe to South America and New Zealand [6]. It occurs in a wide variety of exposed or partly shaded habitats, e.g., on rocks, in low-altitude semi-deciduous woodland, wet evergreen forest and (sub) Montana rain forest.
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