title: Status of self-pollen in bee pollination efficiency of white clover (Trifolium repens L.).
abstract: Flowers of white clover (Trifolium repens L.) are hermaphrodite and self-incompatible; their cross-pollination depends entirely on insect visitors, mainly bees (Apoidea). Because self-pollination of white clover occurs before flower anthesis, we determined whether selfing affected the pollination efficiency of a honeybee visit. We compared pollen deposition in emasculated and intact flowers following (1) a single honeybee visit, (2) open-pollination for a day and (3) enclosure in a cloth bag to prevent insect visits. In emasculated flowers, open-pollination resulted in more pollen deposited than after one visit (+30%) which is consistent with flowers being visited more than once by pollinators during the course of a day. On intact flowers, saturation of the stigma was achieved after the first visit of a honeybee (near 280 grains) because of self-pollination. Additional visits did not increase pollen deposits, but they improved pollen efficiency in terms of numbers of pollen tubes reaching the ovules. In such a context of easily saturated stigmas, self-pollen does not inhibit cross-pollen activity, but represents a constraint for pollination which demands multiple bee visits to each flower to achieve maximum fertilization.
authors.affiliation: I.N.R.A., Equipe de recherche sur la pollinisation entomophile, Station de zoologie et d'apidologie, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon cedex 9, France Fax: (33) 490 31 62 70; e-mail: Guy.Rodet@avignon.inra.fr, , , , , , FR.
authors.forename: Guy
authors.initials: G
authors.lastname: Rodet
authors.affiliation: I.N.R.A., Equipe de recherche sur la pollinisation entomophile, Station de zoologie et d'apidologie, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon cedex 9, France Fax: (33) 490 31 62 70; e-mail: Guy.Rodet@avignon.inra.fr, , , , , , FR.
authors.forename: Bernard E
authors.initials: BE
authors.lastname: Vaissière
authors.affiliation: I.N.R.A., Equipe de recherche sur la pollinisation entomophile, Station de zoologie et d'apidologie, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon cedex 9, France Fax: (33) 490 31 62 70; e-mail: Guy.Rodet@avignon.inra.fr, , , , , , FR.
authors.forename: Thierry
authors.initials: T
authors.lastname: Brévault
authors.affiliation: I.N.R.A., Equipe de recherche sur la pollinisation entomophile, Station de zoologie et d'apidologie, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon cedex 9, France Fax: (33) 490 31 62 70; e-mail: Guy.Rodet@avignon.inra.fr, , , , , , FR.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Torre Grossa
keywords: Honeybees; Key words White clover; Pollen competition; Pollination efficiency; Self-pollen