Browsing by Subject "pollen"

Now showing 1 - 4 of 4
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    (Vol. 03, 2000-12) Phylogenetic Implications of Pollen Morphology and Ultrastructure in the Barnadesioideae (Asteraceae)
    (2000-12) Zhao, Zaiming; Skvarla, John J.; Jansen, Robert K.; DeVore, Melanie L.
    The subfamily Barnadesioideae of the Asteraceae consists of nine genera and approximately 90 species. Both molecular and morphological phylogenies indicate that this subfamily is sister to the rest of the family. We have used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study pollen of 41 species from all genera of the Barnadesioideae. Three general pollen types are described in the subfamily: Barnadesia-type (Barnadesia, Huarpea), Chuquiraga- type (Chuquiraga, Doniophyton, Duseniella, Fulcaldea) and Dasyphyllum-type (Dasyphyllum and Schlechtendalia). A fourth type, Arnaldoa-type, consisting solely of Arnaldoa, is intermediate between the Chuquiraga- and Dasyphyllum-types. These types parallel and confirm findings from previous studies. Psilolophate grains are found only in the Barnadesia-type. Pollen with a cavity (cavea) between pollen wall units in each of the three interapertural regions is present in Barnadesia (Barnadesiatype), Dasyphyllum (Dasyphyllum-type) and Arnaldoa (Arnaldoa-type). The Chuquiraga-type does not have cavate pollen. Intercolpar concavities occur only in the Dasyphyllum- and Arnaldoa-types. In the latter, intercolpar regions are accompanied by pairs of indentations flanking the colpi. The presence of intercolpar concavities in Dasyphyllum and Schlechtendalia, often cited as a synapomorphy for the Barnadesioideae and Calycedceae, has apparently evolved independently within the subfamily. Chuquiraga pollen exhibits the least derived palynological features in the subfamily. Palynological characters, when placed in the context of current phylogenies for the Barnadesioideae, suggest additional phylogenetic analyses are needed to re-evaluate intergeneric relationships within the subfamily.
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    (Vol. 09, 2006-12) Mutisieae (Asteraceae) Pollen Ultrastructure Atlas
    (2006-12) Zhao, Zaiming; Skvarla, John J.; Jansen, Robert K.
    The tribe Mutisieae (excluding Barnadesieae) traditionally comprises 84 genera and approximately 900 species in three subtribes: Gochnatiinae, Mutisiinae, and Nassauviinae. We examined whole and fractured pollen grains of 51 genera from these subtribes by scanning electron microscopy (SEM) and light microscopy (LM). Additionally, we also examined 11 genera (Adenocaulon, Berardia, Brachylaeana, Cratystylis, Dipterocome, Eriachaenium, Gymnarrhena, Hesperomannia, Hoplophyllum, Tarchonanthus, and Warionia) whose tribal positions have been controversial. We present detailed tables of pollen characters for each taxon and 13 plates of SEM photos ofrepresentative taxa. We also provide limited discussion of pollen variation in the subbribes Gochnatiinae, Mutisiinae, and assauviinae and the tribal and subfamilial placement of the 11 problematic genera.
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    (Vol.10, 2007-12) Pollen Morphology and Ultrastructure of Calyceraceae
    (2007-12) DeVore, Melanie L.; Zhao, Zaiming; Jansen, Robert K.; Skvarla, John J.
    Pollen morphology of 13 species from all six genera of Calyceraceae (Acicarpha, Boopis, Calycera, Gamocarpha, Moschopsis, and Nastanthus) and representatives of the Campanulaceae and Goodeniaceae is examined with light (LM), scanning (SEM), and transmission (TEM) electron microscopy. Acicarpha, Calycera, and Nastanthus pollen grains are distinguished by angulaperturate apertures, colpar ledges and surface depressions between colpi known as intercolpar concavities (IC). Pollen of Gamocarpha and Moschopsis is tricolporate rather than angulaperturate and without an IC. Some species of Boopis are similar to the preceding genera (e.g., B. graminea), while others (e.g., B. gracilis) are angulaperturate with ICs. Structural features derived from fractured pollen in SEM and sections in TEM show pollen walls composed of prominent columellae ca. 0.55–1.1 mm high and ,0.25 mm wide. The columellae terminate distally into a complex of shortened columellae ca. 1.5 mm in length and are separated by an illdefined irregular internal tectum layer. This structural complex is well known in several tribes of the Asteraceae and referred to as the Anthemoid type. In those grains with an IC, the structure consists of essentially short (ca. 1 mm), unbranched columellae, similar to those found within the Asteraceae subfamily Barnadesioideae (Dasyphyllum and Schlechtendalia). Goodeniaceae (including Brunonia) pollen has angulaperturate apertures, spinules (i.e., minute spines), problematic IC and some structural similarity to Calyceraceae pollen. The tendency within Calyceraceae to develop colpar ledges, ektexine bridges, and ICs may be a synapomorphy uniting the family with Goodeniaceae. If the ancestral pollen type for the Calyceraceae, Asteraceae, and Goodeniaceae clade is the Gamocarpha type (convex intercolpar regions; no colpar ledges and no ektexine bridges), then the appearance of these structures within each family may be a synapomorphy supporting their close phylogenetic relationship suggested by molecular analyses.