01652nas a2200145   4500008004100000245007400041210006900115260000800184300001200192490000700204520121300211100001701424700001701441856004801458       2003                        eng d00aComparative development of aseptate and septate anthers of Annonaceae0 aComparative development of aseptate and septate anthers of Annon  cJun  a832-8480 v903 aWe 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.1 aTsou, C., H.1 aJohnson, D M  uhttps://annonaceae.myspecies.info/node/5613