@article {5611,
	title = {Tetrad pollen formation in Annona (Annonaceae): Proexine formation and binding mechanism},
	journal = {American Journal of BotanyAmerican Journal of Botany},
	volume = {89},
	number = {5},
	year = {2002},
	month = {May},
	pages = {734-747},
	abstract = {Meiotic tetrads of Annona glabra and A. montana build up a well-developed proexine (protectum, probaculum, and pronexine) at the proximal side but only a thin pronexine at the distal side during the tetrad stage. The callosic envelope is only partially digested by the end of tetrad stage. The remaining, undigested part is composed of the intersporal mass and thin peripheral layers, and the latter is conjunct with the distal pronexine of the microspore. In this remaining callosic structure celluloses are also present. Later on, due to the continuous slow decomposition of this callose-cellulose structure and microspore expansion, microspores break up the callose-cellulose envelope. Because all the four microspores are bound together by the callose-cellulose structure, they move out of the chamber in rotation. Eventually the thin pronexine is pulled toward the center of the tetrad and the well-developed proexine becomes the distal wall. These descriptions of the partial digestion of callosic envelope, the transformation from a callose-cellulose structure to the binding system of tetrad pollen, and microspore rotation in Annona are unusual in the angiosperms.},
	author = {Tsou, C. H. and Fu, Y. L.}
}
@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 {5613,
	title = {Comparative development of aseptate and septate anthers of Annonaceae},
	journal = {American Journal of BotanyAmerican Journal of Botany},
	volume = {90},
	number = {6},
	year = {2003},
	month = {Jun},
	pages = {832-848},
	abstract = {We compared anther development in 13 genera and 15 species of Annonaceae to document the nature and development of anther septa. In aseptate anthers, all sporogenous initials proceed to sporogenesis and meiosis. In septate anthers, a small number of sporogenous initials, in a discontinuous distribution pattern, differentiate into sporogenous cells; the remaining initials become sterile and form cellular septa that partition each anther lobe into multiple sporangial chambers. In species where the septum is 1-2 cell layers thick, the entire septum becomes tapetal (T-type septa) and breaks down before anther dehiscence. In species in which the septum is three or more cell layers thick, only the layer in direct contact with the sporogenous cells becomes tapetal, and the remaining cells become parenchymatous (P-type septa). These thicker P-type septa are sometimes visible in dehisced anthers. Both types are homologous in ontogeny and are highly associated with the production of compound pollen. We propose that the evolution of anther septation in Annonaceae was mainly driven by the requirement for highly efficient nutrient and physical support to the development of large, compound pollen units.},
	author = {Tsou, C. H. and Johnson, D. M.}
}
