@article {5612,
	title = {Octad pollen formation in Cymbopetalum (Annonaceae): the binding mechanism},
	journal = {Plant Systematics and EvolutionPlant Systematics and Evolution},
	volume = {263},
	number = {1-2},
	year = {2007},
	month = {Jan},
	pages = {13-23},
	abstract = {Our recent study of tetrad pollen formation in Annona (Annonaceae) revealed that after meiosis the callose-cellulose envelope forms a special conjugation with individual microspores and the forthcoming callose digestion is incomplete. The undigested part forms a central binder holding the four microspores of the tetrad together. This process causes the microspores to rotate 180 degrees. In this paper we describe pollen formation in another annonaceous genus, Cymbopetalum, in which the pollen is shed in octads, through use of light microscopy, epifluorescence microscopy, and TEM. In Cymbopetalum, two meiocytes, connected by abundant cytomictic channels, are produced in each sporangium. Octad pollen formation in Cymbopetalum is shown to be comparable to the synchronized formation of two connected Annona tetrads, which then integrate into a single octad. Unique features of Annona polyad formation, e.g. special binding between the callose-cellulose envelopes and microspores, incomplete callose digestion, and microspore rotation, also occur in Cymbopetalum. In addition, formation of the Cymbopetalum octad involves development of a cushion-like structure that binds the distal pronexine of all eight microspores, and there is the production of intine protrusions. The evolutionary origin of the callose-cellulose binding mechanism within the family is discussed.},
	keywords = {angiosperms, Annona, Annonaceae, ASIMINA-TRILOBA ANNONACEAE, CALLOSE DISSOLUTION, callosic envelope, compound pollen, Cymbopetalum, DEVELOPMENTAL, EVENTS, EVOLUTION, GENERA, microspore rotation, octad pollen, SPORODERM DEVELOPMENT, TAPETUM, TETRADS},
	isbn = {0378-2697},
	author = {Tsou, C. H. and Fu, Y. L.}
}
@article {5041,
	title = {Significance of palynology for phylogeny of Annonaceae: Experiments with removal of pollen characters},
	journal = {Plant Systematics and EvolutionPlant Systematics and Evolution},
	volume = {206},
	number = {1-4},
	year = {1997},
	pages = {133-159},
	abstract = {Phylogenetic analyses based on morphology place Anaxagorea and other taxa with granular monosulcate pollen, as in other Magnoliales, at the base of Annonaceae. Taxa with columellar tetrads, granular tetrads, and inaperturate monads form a derived clade. To test the systematic importance of palynology, we analyzed the data set with pollen characters removed. The result was lower resolution and a different rooting of the family, between Uvariopsis and other groups with columellar tetrads. Anaxagorea and other monosulcates are higher in the tree, implying that granular monosulcate pollen, laminar stamens, and irregular endosperm ruminations are reversals. This rooting is highly unparsimonious when pollen characters are included, and only weakly supported over the Anaxagorea rooting when pollen is excluded. Together with preliminary molecular analyses, these experiments confirm the special value of palynology in systematics of Annonaceae.},
	keywords = {Annonaceae, cladistics, EVOLUTION, GENERA, Magnoliales, palynology, phylogeny, SYSTEMATICS, ULTRASTRUCTURE},
	author = {Doyle, J. A. and LeThomas, A.}
}
