Functional analysis of synchronous dichogamy in flowering rush, Butomus umbellatus (Butomaceae)
Dichogamy is one of the most widespread floral mechanisms in flowering plants and is thought to have evolved to reduce interference between pollen import and export within flowers, especially self‐pollination. Self‐pollination between flowers may also be reduced if dichogamy is synchronous among flo...
| Published in: | American Journal of Botany |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2001
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.2307/3558382 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F3558382 http://onlinelibrary.wiley.com/wol1/doi/10.2307/3558382/fullpdf |
| Summary: | Dichogamy is one of the most widespread floral mechanisms in flowering plants and is thought to have evolved to reduce interference between pollen import and export within flowers, especially self‐pollination. Self‐pollination between flowers may also be reduced if dichogamy is synchronous among flowers on an inflorescence. The analysis of dichogamy at both levels requires that the sexual phases of individual flowers be defined functionally in terms of pollen deposition and removal. We conducted morphological and functional analyses to investigate the degree of dichogamy within flowers and the synchronicity of dichogamy between flowers within inflorescences in an emergent, aquatic monocot, flowering rush ( Butomus umbellatus ). Based on daily observations of the development of marked flowers, data on the schedule of anther dehiscence within flowers, and repeat surveys of floral sex ratios in three populations, individual flowers appear to be strictly protandrous. On average, each flower spends ∼1 d in each of male and female phases with an intervening 1‐d neuter phase during which there is no available pollen in anthers and stigmas are not yet exposed to receive pollen. Morphological criteria used to delimit the beginning and end of each of these three sex phases were validated by quantifying the temporal schedule of pollen removal from anthers and pollen deposition on stigmas. Experimental pollinations showed that the morphological changes marking the end of female phase are hastened by pollen deposition. At the umbel level, synchronous development within sequential cohorts of flowers reduced overlap of male and female sexual phases between flowers. On average (±1 SE), 72 ± 3% of flowers completed their female phase while no other flowers on the same umbel were in male phase. Computer simulations of umbel development showed that this value is significantly higher than expected if the timing of flower development within umbels was random (30 ± 1%). Surveys of floral sex ratios in three populations revealed that ... |
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