Patterns of fruit and seed set within inflorescences of Pancratium maritimum (Amaryllidaceae): nonuniform pollination, resource limitation, or architectural effects?

Abstract

We investigated patterns of fruit and seed production on inflorescences of a population of Pancratium maritimum in northwest Spain over a 2-yr period. Initial findings showed that the earliest opening flowers on an inflorescence are more likely to set fruit and produce more seeds than later opening flowers and that this pattern is maintained throughout the flowering season. Supplementary pollination and flower-removal experiments were performed to investigate whether the observed pattern is attributable (a) to variation in pollen receipt, (b) to sequestration of resources by the earliest flowers on an inflorescence, and/or (c) to "architectural" limitations on the fruit/seed production of later flowers. Supplementary pollination did not improve fruit or seed production by late flowers in either of the 2 yr of study. In flower-removal experiments, the remaining flowers showed improved fruit set and mean number of seeds per flower, by comparison with flowers in the same position on control inflorescences. When all flowers except the latest third were removed, these showed fruit set and seed production similar to those of early flowers on control inflorescences. These results strongly suggest that the observed within-inflorescence patterns of fruit and seed production in P. maritimum are mainly attributable to competition for resources (i.e., explanation b), though other adaptive explanations cannot be ruled out.

Diversity of wild bees supports pollination services in an urbanized landscape

“…In particular, fruit set may indicate simple presence/absence of pollinator visits (Pellissier et al 2012), whereas seed set may be a better indicator of total pollen transfer by particular pollinators (Medrano et al 2009). We found pollinator visits to best explain fruit set in cucumbers but seed set in eggplant.…”

Fruit size decline from the margin to the center of capitula is the result of resource competition and architectural constraints

“…Although fruit size and/or fruit set declines have been shown in several species in earlier studies (reviewed in Diggle 2003), these were attributed either to competition for resources (Medrano et al 2000;Vallius 2000;Kliber and Eckert 2004) or to architectural constraints (Byrne and Mazer 1990;Wolfe and Denton 2001;Guitián et al 2001). Very likely, the relative importance of architectural constraints and resource competition is species-or even trait-speciWc (Ashman 1992;Wolfe 1992;Diggle 1997;Ashman and Hitchens 2000;Kliber and Eckert 2004).…”

Reproductive biology of threeZiziphusspecies (Rhamnaceae)

“…Viable seed set under open pollination was studied since open pollination studies are a better indication of maximum reproductive potential, as a measure of reproductive success in comparison to controlled pollination conditions ( Liu, P. 2008). This has been verified in other plant species (Medrano et al 2000;Dhar et al 2006). Self as well as cross incompatibility between various Z. mauritiana genotypes is well known (Pareek, O.P.…”