Plant extrafloral nectaries

Definition

Secretory structures on vascular plants that produce nectar at sites other than flowers, typically located on leaves, stems, petioles, or bracts. Unlike floral nectaries that reward pollinators, extrafloral nectaries function primarily in indirect defense: they attract ants, predatory wasps, and other arthropod bodyguards that protect the plant against herbivores. The nectar is generally more dilute and chemically distinct from floral nectar, lacking the specific amino acid profiles that attract pollinators.

Etymology

Latin extra (outside, beyond) + floralis (of a flower) + nectar (sweet liquid) + -ium/-ia (structure)

Example

The bullhorn acacia (Vachellia cornigera) maintains a mutualism with Pseudomyrmex ants: paired extrafloral nectaries at each petiole base and protein-rich Beltian bodies on leaf tips feed the colony, while the ants aggressively attack herbivores and vines that contact the plant.

Synonyms

• EFNs
• extrafloral nectarines (obsolete)

Related Terms

• floral nectaries
• myrmecophily
• induced plant defense
• trophic mutualism
• Ant-plant interactions
• herbivory
• domatia
• Beltian bodies
• food bodies

Usage Notes

Distinguished from floral nectaries by location, function, and nectar chemistry; the term is sometimes shortened to EFNs in ecological literature. Not all plants with EFNs are myrmecophytes—some attract generalist predators or parasitoids. Presence and secretion rate often increase in response to herbivore damage (induced defense). Contrast with 'floral nectaries' (pollinator rewards) and 'food bodies' (solid lipid/protein rewards rather than liquid secretions).