Nectar regulation in Euphorbia tithymaloides L., a hummingbird-pollinated Euphorbiaceae.

VEIGA T; GALETTO L; MACHADO IC

PLANT BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012

1435-8603

ABSTRACTFloral sexual phases can differ in nectar production and might be under selective pres-sure by pollinators. We studied Euphorbia tithymaloides, which has inflorescencesthat are initially female and then hermaphroditic. Volume and concentration of nectarwere measured in both stages. Nectar production and the effect of extractions weredetermined using sets of bagged inflorescences; inflorescences in the hermaphroditicphase had higher values of nectar concentration, volume and sugar mass than inflores-cences in the female phase. Nectar resorption was detected in senescent inflorescences.To test for homeostatic nectar regulation, artificial nectar was added and the responseassessed after 24 h. The experiments showed that concentration and sugar mass areregulated within a narrow range, and the homeostatic points differ between the twosexual phases. These differences in nectar can be detected by hummingbirds, whichprefer the female stage. Resorption and secretion seem to be part of a homeostaticmechanism by which nectar attributes are maintained to optimise sugar recovery.