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How do Asteraceae differ from the related Calyceraceae family?
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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.
While the Asteraceae and Calyceraceae families are closely related and share similar characteristicsâsuch as being members of the Asterales order, possessing involucrate heads, and utilizing a specialized plunger pollination mechanismâthey are distinguished by key botanical differences.1234
The most significant feature distinguishing the two families is the position of the ovule within the ovary:
- Asteraceae: The ovule is basal, meaning it arises from the base of the ovary.3
- Calyceraceae: The ovule is pendulous, meaning it hangs from the top of the ovary.3
Additionally, while both families feature flowers arranged in heads, they differ in their floral anatomy. In Asteraceae, the calyx is typically highly modified into a pappus consisting of scales, awns, or bristles. In contrast, Calyceraceae flowers have sepals that are either thick and spongy or transformed into spines.34