Abstract
Corollas (or perianths), considered to contribute to pollinator attraction during anthesis, persist after anthesis in many plants. However, their post-floral function has been little investigated within a cost-benefit framework. We explored the adaptive significance of corolla retention after anthesis for reproduction in Fritillaria delavayi, a perennial herb endemic to the alpine areas of the Hengduan Mountains, southwestern China. We examined whether the persistent corollas enhance reproductive success during seed development. Persistent corollas increased fruit temperature on sunny days, and greatly decreased the intensity of ultraviolet-B/C (UV-B/C) radiation reaching fruits. When corollas were removed immediately after pollination, fecundity and progeny quality were adversely affected. Measurements of flower mass and size showed no further corolla growth during fruiting, and respiration and transpiration tests demonstrated that both respiration rate and transpiration rate of corollas were much lower during fruiting than during flowering, indicating a slight additional resource investment in corolla retention after anthesis. Thus, seed production by F. delavayi may be facilitated by corolla retention during seed development at only a small physiological cost. We conclude that corolla retention may be an adaptive strategy that enhances female reproductive success by having a protective role for ripening seeds in the harsh conditions at high elevation.
Highlights
In order to ensure reproductive success, flowering plants exhibit an astonishing diversity of floral traits; these include different colors of petals[1,2], variable flower orientation[3,4], individual flower movement[5,6], and extrafloral structures[7,8]
We demonstrate that corolla removal after flowering has a significantly negative effect on seed development, adversely affecting seed set, abortion rate, and seed mass, suggesting that corolla retention in F. delavayi facilitates the development of fertilized ovules during fruiting
Our results show that the persistent corollas of F. delavayi can increase the interior temperature of fruits by as much as 8 °C compared with the ambient air temperature on sunny days, and this may provide a favorable thermal environment for ripening seeds, promoting seed development
Summary
In order to ensure reproductive success, flowering plants exhibit an astonishing diversity of floral traits; these include different colors of petals[1,2], variable flower orientation[3,4], individual flower movement[5,6], and extrafloral structures[7,8]. As dark flowers have been found to absorb solar radiation efficiently[26], in combination with the high effectiveness of corollas or perianths in blocking UV radiation which has been documented in many plant species[3,27,28], we hypothesized that the dark, closed corolla of F. delavayi may facilitate the development of fertilized ovules by increasing interior temperature and forming a protective barrier against ultraviolet radiation To test this hypothesis, we examined (1) the effect of corolla retention on interior temperature and intensity of UV-B/C radiation; (2) the possible costs of corolla retention in terms of growth (increase in biomass), respiration and transpiration; (3) the effect of corolla retention during seed ripening on female fitness
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