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How does the keel of a Faboideae flower help with pollination?
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Fabales
A flowering stalk of yellow partridge pea (Chamaecrista fasciculata) in the eastern United States.
In the subfamily Faboideae (also known as Papilionoideae), the keel is formed by two lower petals that are typically fused together. This structure plays a vital role in pollination by enclosing and protecting the flower's reproductive organsāthe stamens and the pistil.1
The keel functions as part of a specialized mechanism adapted for insect or hummingbird pollination. It works in conjunction with the other petals, such as the banner and the lateral wings, to create a complex system of locking and releasing devices. When a pollinator visits the flower, these devices control the exposure of the reproductive parts, effectively favoring or enforcing either cross-pollination or self-pollination.1