Developmental and Structural Section
Mickle, James , Barone Lumaga, Maria Rosaria , Moretti, Aldo , De Luca, Paolo .
Systematic Implications of Cuticular Micromorphology of Microcycas (Cycadales).
Microcycas (Miquel) A. DeCandolle (Cycadales) is a rare, monotypic cycad genus endemic to western Cuba. Whole leaf and isolated cuticle specimens from Microcycas calocoma were examined using SEM for external and inner surface features and three-dimensional stomatal complex structure, taxonomically useful characteristics. Samples from the middle of leaflets from the midregion of mature leaves of plants were obtained from the University of Naples (Italy) Botanical Garden greenhouse. Samples were fixed in FAA, and cuticles isolated using 20% CrO3 to study inner surfaces. Characteristics of M. calocoma include hypostomy, abaxial and adaxial cells arranged parallel to the leaflet long axis. Adaxial exterior cuticle is smooth but with fine striations parallel to the cell long axis. Adaxial interna lepidermal cells are elongate with a granular internal surface; intercellular flanges are low and indistinct with irregular files of cells displaying higher,more distinct flanges. Stomatal complexes are diperigenous, oriented parallel to veins and in loosely arranged rows on ridges parallel between veins. Stomata are shallowly sunken. Aperture between guard cells possesses a thick flange and extend the entire length of the stomatal complex. Prominent polar extensions are evident. Guard cell walls are rugose laterally. Abaxial epidermal cells are elongate with a granular cuticular surface internally. The external abaxial surface shows fine striations on the cuticular surface. There are marked rings around stomatal openings. Microcycas shows its greatest overall similarity in cuticular micromorphology to other membersof the Zamiaceae, with marked similarities in cuticular micromorphology to Zamia and Ceratozamia. Recent molecular studies have suggested that the monotypic genus Stangeria is a sister group to Ceratozamia, within a grouping that also includes Microcycas, Chigua, and Zamia. Microcycas is used here as an example of the grouping into which Stangeria has been placed by these recent molecular studies. Stangeria shows a number of cuticular microphorphological features, such as distinct striations extending from stomatal poles and hair bases, and a unique stomatal complex surrounded by a cuticular flange with a serrate margin that are not observed in other cycads. Because these cuticular micromorphological characters are useful phylogenetically, and these features clearly show marked differences between Microcycas and Stangeria, cuticular micromorphology does not support the close relationship suggested by recent studies and reinforces morphological studies that places Microcycas as a sister group to Zamia and places Stangeria as a unique genus within the cycads.
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1 - North Carolina State University, Plant Biology, Campus Box 7612, 2115 Gardner Hall, Raleigh, NC, 27695-7612, USA
2 - Universita' di Napoli Federico II, Orto Botanico, via Foria, 223, Napoli, 80139, Italy
3 - Universita' di Napoli Federico II, Scienze Biologiche, Sez. di Biologia Vegetale, via Foria, 223, Napoli, 80139, Italy
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM