Embryo sac development in Vanroyenella plumosa, Podostemaceae

Abstract

Species of Podostemaceae grow in rapidly flowing tropical rivers, streams and water falls, strongly attached to rock substrates via expanded, adhesive-secreting holdfasts (haptera). Vanroyenella is a monotypic genus endemic to Mexico, occurring in the northern extent of the tropical distribution of Podostemaceae in the New World. Embryo sac development and nucellar plasmodium formation of Vanroyenella plumosa Novelo and Philbrick was studied. The numerous ovules are anatropous, bitegmic, exostomous, and terminucellate, each with a four-celled monosporic embryo sac of the Apinagia type. Disintegration of the nucellus into a plasmodium takes place prior to fertilization. Embryo sac development of Vanroyenella is similar to other members of the Podostemoideae subfamily. (C) 2002 Elsevier Science B.V. All rights reserved.