Desenvolvimento de óvulo, fruto e semente de espécies de Poaceae (Poales)

Abstract

-(Ovule, fruit and seed development in species of Poaceae (Poales)). We selected Olyra humilis Nees and Sucrea monophylla Soderstr. (Bambusoideae), Axonopus aureus P. Beauv. and Paspalum polyphyllum Nees ex Trin. (Panicoideae), Chloris elata Desv. and Eragrostis solida Nees (Chloridoideae) to study their ovule, fruit and seed development in order to characterize the embryology of these subfamilies within Poaceae. Like other Poaceae that have already been studied, these species present bitegmic ovule, micropyle formed by the inner integument, megagametophyte of the Polygonum type, starchy nuclear endosperm, and lateral, developed embryo. In specimens of Bambusoideae and Panicoideae, the ovule is hemianatropous and pseudocrassinucellate, whereas in Chloridoideae, it is campylotropous and tenuinucellate. The outer integument is restricted to the ovule base in Bambusoideae; it reaches up to one third of the nucellus in Panicoideae and extends to the micropyle in Chloridoideae. O. humilis and S. monophylla (Bambusoideae) present a more developed nucellus than the other species studied here. Each subfamily varies with regard to its mature caryopsis type. In Bambusoideae, the fruit has a phenolic endocarp and ategmic seeds; Panicoideae have compressed, adnate pericarp and tegmen; Chloridoideae present a free exocarp and a phenolic endotegmen. The overall features are diagnostic for the Poaceae subfamilies studied here.Key words -Bambusoideae, Chloridoideae, embryology, Panicoideae RESUMO -(Desenvolvimento do óvulo, fruto e semente de espécies de Poaceae (Poales)). O desenvolvimento de óvulo, fruto e semente de Olyra humilis Nees e Sucrea monophylla Soderstr. (Bambusoideae), Axonopus aureus P. Beauv. e Paspalum polyphyllum Nees ex Trin. (Panicoideae), Chloris elata Desv. e Eragrostis solida Nees (Chloridoideae) foram estudados visando à caracterização embriológica dessas subfamílias de Poaceae. As espécies apresentam óvulo bitegumentado, micrópila formada pelo tegumento interno, megagametófito tipo Polygonum, endosperma nuclear e amiláceo, embrião lateral e desenvolvido, caracteres comuns às demais espécies de Poaceae já estudadas. Destacam-se diferenças como: óvulo hemianátropo e pseudocrassinucelado nas espécies de Bambusoideae e Panicoideae, campilótropo e tenuinucelado, nas de Chloridoideae; tegumento externo restrito à base do óvulo em Bambusoideae, até um terço do nucelo em Panicoideae e próximo à região micropilar em Chloridoideae. O. humilis e S. monophylla (Bambusoideae) apresentam maior desenvolvimento do nucelo do que as demais espécies. A variação no tipo de cariopse separa as subfamílias de Poaceae estudadas, pois Bambusoideae apresenta endocarpo fenólico e semente ategumentada; Panicoideae apresenta pericarpo comprimido e adnato ao tégmen; e Chloridoideae apresenta exocarpo livre e endotégmen fenólico. Esses caracteres são diagnósticos para as subfamílias de Poaceae estudadas.

Recent Trends in Research on the Genetic Diversity of Plants: Implications for Conservation

“…The family Poaceae was represented by the largest number of species in the papers published on research in genetic diversity that has used cpDNA sequences as molecular markers. This prominence was predictable, given the economic importance and, to a certain extent, the ecological relevance of this family, which is one of the most widely-studied angiosperm groups [60]. The Pinaceae and Rosaceae were also prominent in terms of both the number of species and publications.…”

Ovule, fruit and seed development inAbolboda(Xyridaceae, Poales): implications for taxonomy and phylogeny

“…A possible function of this tanniferous layer is to protect the seeds against fungi and/or herbivores as they have a starchy endosperm. In addition to the xyrids, a tanniferous tegmen was observed in the seeds of the following poalean families: Centrolepidaceae (Hamann, ); Rapateaceae (Venturelli & Bouman, ); Restionaceae (Rudall & Linder, ); and Poaceae (Nakamura, Longhi‐Wagner & Scatena, ).…”