MUSSELMAN, LYTTON JOHN. Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266. - Surface Features of Quillwort (Isoetes, Isoetaceae, Lycophyta) Microspores.
Surface Features of Quillwort (Isoetes, Isoetaceae, Lycophyta)
Microspores Lytton John Musselman, Department of Biological
Sciences, Old Dominion University, Norfolk, Virginia 23529-0266
Traditionally, the surface features of Isoetes megaspores have
provided the foundation for determining species. Microspores, on the
other hand, have been largely neglected in taxonomic schemes and no
descriptors for ornamentation have been widely used other than
spinulose, papillate, tuberculate, and smooth. Using species from
Africa, Asia, Australia, Europe, and North and South America, I
examined microspore ornamentation with the scanning electron
microscope. Ornamentation and sculpturing of microspores are more
diverse than previously reported. Aculate, cristate, echinate,
rugulate, and verrucate macro-ornamentation were found in different
taxa. Bacillate and fimbriate micro-ornamentation characterize a
diversity of species. Surface features vary on the three faces of the
microspore (two proximal, one distal surface, and the single ridge).
Based on this limited sampling, species with higher ploidy level have
larger microspores but no clear relationship between microspore
ornamentation and ploidy level was established nor were any
geographical or ecological trends clear. Species with unornamented or
psilate microspores are few and reports of this trait could be due to
examination of immature spores. Like megaspores, microspores of
hybrids are polymorphic, varying both in size and sculpturing.