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

Abstract

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.