Diversity and evolution of microsporogenesis in Bromeliaceae

In this study, we explore the features of microsporogenesis in Bromeliaceae and, in particular, the diversity and evolution of additional callose deposits. Cytokinesis type, cell wall formation, tetrad form and patterns of additional callose deposition after intersporal wall formation were studied in 12 species of Bromeliaceae (each from a different genus) presenting four different aperture patterns. Microsporogenesis is highly conserved, with successive cytokinesis, centrifugal cell plate formation and predominantly tetragonal and decussate tetrads, as in many monocots, but five different patterns of additional callose deposition were recorded. The optimization of patterns of additional callose deposition on the phylogeny of Bromeliaceae reveals convergences. Additional callose deposition is a variable and labile feature of microsporogenesis in Bromeliaceae and is linked, to some extent, to aperture pattern. (C) 2014 The Linnean Society of London