Achene

Achene

An achene is a type of simple dry fruit produced by many species of flowering plant. Achenes are characterized by a single seed that is enclosed in a hard, indehiscent outer shell. This means that the seed does not naturally open to release the seed when it is mature. Achenes are a common fruit type in the Asteraceae family, which includes plants such as sunflowers and dandelions.

Morphology

The structure of an achene consists of a single seed that is attached to the pericarp (the fruit wall) at a single point. The pericarp is typically thin and does not fuse with the seed coat, allowing the seed to be easily separated from the fruit. This is in contrast to other fruit types such as caryopsis, where the seed coat is fused to the pericarp.

Longitudinal section showing achene formation in Rosa

Types of Achenes

Cypsela

A cypsela is a type of achene that is derived from an inferior ovary, typical of the Asteraceae family. The cypsela often has a pappus, which is a modified calyx that aids in wind dispersal.

Cypsela of Cynara

Samara

A samara is a winged achene, which aids in wind dispersal. This type of fruit is common in trees such as maples (Acer).

Samara of Acer buergerianum

Dispersal Mechanisms

Achenes are often adapted for dispersal by wind, water, or animals. The presence of structures such as pappi or wings can enhance the ability of the achene to be carried over long distances.

Wind Dispersal

Many achenes, such as those of the dandelion (Taraxacum), have a pappus that acts like a parachute, allowing the seed to be carried by the wind.

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Dandelion achenes ready for wind dispersal

Animal Dispersal

Some achenes are adapted to be dispersed by animals. They may have hooks or barbs that attach to animal fur, or they may be ingested and later excreted by animals.

Examples of Plants with Achenes

• Dandelion (Taraxacum)
• Sunflower (Helianthus)
• Buttercup (Ranunculus)
• Strawberry (Fragaria)

Related Pages

• Fruit
• Seed
• Dispersal (botany)
• Asteraceae

Gallery

• 
  Microscopic view of dandelion achenes
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  Achenes of Pulsatilla alpina
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  Coreopsis tinctoria cultivar with achenes
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  Close-up of Coreopsis tinctoria achenes