A Scanning Electron Microscopy Study of the Seed and Post-seminal Development in Angelonia salicariifolia Bonpl. (Scrophulariaceae)

The external morphology of seeds and post-germination developmentalstages of Angelonia salicariifolia Bonpl. (Scrophulariaceae)were investigated using scanning electron microscopy. Some structuralfeatures of the seed exotesta and seedling in Angelonia arepresented for the first time and are of potential taxonomicvalue for this neotropical genus. The seeds are very small (0.9–1.7mm long and 0.5–0.9 mm wide), ovate, with a reticulate-crestedexotesta, reticules arranged uniformly in longitudinal rows,with a high density of microcilia-like projections on the cellwall of the reticule base and on the edge of the crests. Thehilum is located beside the micropyle at the narrow end of theseed. Germination is epigeal. During germination the radicledevelops, followed by elongation of the hypocotyl and primaryroot. At this stage dense root hairs develop on the lower partof the hypocotyl. The apical bud—located between the cotyledons—beginsto develop after the cotyledons have unfolded. The cotyledonsare equal in size, sessile and ovate. The seedlings have twotypes of trichomes, one characteristic of the cotyledons andfirst pair of leaves (glandular, sessile, four-celled head withquadrangular shape) and the other characteristic of the hypocotyland epicotyl (stalked, erect, elongate and three-celled withdome-shaped unicellular head). Copyright 2001 Annals of BotanyCompany Seed morphology, exotesta-ornamentation, micromorphology, post-seminal stages, seedling, trichomes, SEM, Angelonia salicariifolia Bonpl., Scrophulariaceae