Before and after flowering: patterns of flower, ovule and seed formation in an annual hemiparasitic plant, Rhinanthus major (Orobanchaceae)
(2019) XVI EcoFlor 2019 — Location: Granada, Espagne (14.March.2019)
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- Plants in the genus Rhinanthus are annual hemiparasites with can use a large range of grassland species (mainly grasses and legumes) as hosts. The vernal ecotype, which occurs in hay meadows, has a relatively short life cycle, as seed maturation should be completed before mowing. Plant biomass in R. major is highly dependent on attachment to a good host and local conspecific density, and it can vary strongly among plants. Biomass determines the amount of resources available for flower and ovule formation before anthesis and for formation of the relatively heavy (2–3 mg) seeds after flowering. Visitation rates to R. major are high, so pollen limitation is unlikely to play in role in seed set patterns. We studied patterns of flower bud abortion, ovule numbers and seed production in naturally developing plants and in plants in which flowers at 6 out of 8 nodes in the inflorescence had been removed just before opening, to reduce resource competition. Small plants had a higher rate of flower bud abortion overall, and within inflorescences the highest rates of flower bud abortion were found on the first (basal) and last node of the inflorescence. Ovule production did not vary with flower position within the inflorescence, but a higher plant biomass increased the number of ovules produced per flower. In control plants, seed set per flower decreased from the bottom to the top of the inflorescence. In the treatments with a reduced flower number, seed production increased in the remaining flowers. Each capsule has an upper and a lower locule, and the ovules are arranged horizontally along the two placenta in each locule. An upper locule contains on average 8.1 (two rows of 4) ovules, with slightly more ovules in the lower locule (8.6), with rarely 6 ovules per row. Seed set in the control plants was around 0.4, while this was 0.5-0.65 in the treated plants. Unexpectedly, seed set was highest in the central and distal ovules: in both locules, the first (basal) ovule set seed only half as often as the second ovule. Treated plants increased seed set at all ovule positions. We discuss the possible explanations for these patterns.
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Saulnier, A., & Wesselingh, R. (2019). Before and after flowering: patterns of flower, ovule and seed formation in an annual hemiparasitic plant, Rhinanthus major (Orobanchaceae). XVI EcoFlor 2019, Granada, Espagne. https://hdl.handle.net/2078.5/93977