@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 {669,
	title = {Evolution and phylogenetic significance of pollen in Annonaceae},
	journal = {Botanical Journal of the Linnean Society},
	volume = {169},
	number = {1},
	year = {2012},
	pages = {190-221},
	publisher = {Blackwell Publishing Ltd},
	abstract = {The remarkable diversity of pollen morphology in Annonaceae has attracted systematic attention since the 1970s. Optimization of pollen characters on a molecular tree confirms that granular monosulcate pollen, as in Anaxagorea and subfamily Ambavioideae, was ancestral in the family. However, granular structure is derived for angiosperms as a whole, and exine characters are highly homoplastic in Annonaceae. Because columellar taxa (Annickia, Bocageeae) diverged earlier than previously thought, columellae may have re-originated in the common ancestor of Malmeoideae and Annonoideae, which make up most of the family, with several later reversals to granular structure. In Malmeoideae, loss of the sulcus and origin of a verrucate tectum occurred in the tribe Miliuseae, followed by an uncertain number of origins of disulculate pollen. Tetrads arose several times in Annonoideae, but reverted to monads in Isolona and probably Uvarieae. Recognition that microspores rotate during development in Annona and Cymbopetalum suggests that the proximal thin area in these taxa is a modified distal sulcus, but rotation does not occur in all tetrad groups; a broader survey is needed to evaluate this phenomenon.~{\textcopyright} 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 190{\textendash}221.},
	keywords = {angiosperms, Magnoliales, morphology, palynology, phylogeny, SYSTEMATICS},
	isbn = {1095-8339},
	url = {http://dx.doi.org/10.1111/j.1095-8339.2012.01241.x},
	author = {Doyle, James A. and Le Thomas, Annick}
}
