The anatomy and pollination of subterranean cleistogamous flowers of Benghal
dayflower (Commelina benghalensis) is described as a
contribution to understanding its reproductive biology. Subterranean stems
bear one spathe per node, each enclosing a single cleistogamous flower. Only
the three anterior stamens produce functional pollen; the posterior three
stamens are staminodes. Tapetum is amoeboid and endothecium is present. The
three-carpellate superior ovary bears five dimorphic orthotropous ovules.
Nearly mature flowers have straight to somewhat curved styles; at maturity,
styles elongate and coil. Our observations indicate that coiled style growth
causes rupture of anthers and brings pollen into contact with stigmas.
Pollen tubes were observed in styles that had previously undergone coiling,
located within mucilaginous secretions of the mature stylar canal. The
subterranean cleistogamous flowers of Benghal dayflower and their apparently
unique mode of pollination, viewed together with reproductive capacity of
its aerial chasmogamous flowers, underscore the complexity and flexibility
of the reproductive biology of this noxious weed species.