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How are sepals modified into a pappus in Asteraceae plants?

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Sunflower — Asteraceae The flowering head of a sunflower (*Helianthus annuus*) is formed of yellow, petal-like ray flowers and a brown center of minute disk flowers.

In the plant family Asteraceae, the calyx—the collective term for sepals—is so highly modified that it is referred to as the pappus.1

Rather than appearing as typical sepals, the pappus manifests as a collection of dry scales, small pointed processes known as awns, or hairlike capillary bristles. In some species, these structures may be joined by their margins to form a crownlike ring at the summit of the ovary. While these modifications are extensive, they remain homologous to sepals, as evidenced by a few genera, such as Marshallia, where the calyx consists of five clearly defined, regularly placed scales.1

This specialized structure serves a vital ecological function: it aids in seed dispersal by providing buoyancy for wind transport or, when barbed, by allowing the fruit to attach to animals for distribution.2