Seed formation and pollination system in Cuscuta obtusiflora: First record of preanthesis cleistogamy in parasitic plants and some functional inferences

With the purpose of increasing the currently available data on reproductive biology about Neotropical Cuscuta species in general, and mode of reproduction and seed ontogeny in Cuscuta obtusiflora H.B. and K. in particular, both developing flowers and seeds have been analysed by means of standard photomicroscopy together with histological techniques, stereomicroscopy, fluorescence microscopy and field observation.Meiosis of a single archesporocyte originates linear megasporic tetrads with chalazal viability. The megagametophyte belongs to the Polygonum type. Porogamous fertilisation occurs prior to perianth opening. From the apical proembryonal cell ca the rudimentary coiled embryo proper originates, formed mostly by the hypocotyl. A broad suspensor is derived from the frequently vesicular basal cell