Exine
Definition
The tough outer wall of a pollen grain, composed of sporopollenin. Carries the diagnostic sculpture and aperture features and survives most preservation conditions that destroy other biological material.
- Composition
- Sporopollenin
- Structure
- Tough outer wall of a pollen grain
- Value
- Carries diagnostic sculpture and aperture features
- Preservation
- Survives conditions that destroy most other biological material
Common questions
Why is the exine so resistant to decay compared to other plant material?+
Sporopollenin is one of the most chemically stable biopolymers known, resisting acids, enzymes, and microbial breakdown, which is why pollen exines can survive in soil, sediment, and even fossil deposits long after the rest of the plant has decomposed.
What does the exine's surface pattern allow a palynologist to determine?+
The sculpture and aperture arrangement on the exine surface are species-specific or genus-specific under microscopy, letting an examiner identify the source plant and, from that, link evidence to a location, season, or environment.
Related terms
- Aperture
- An opening in the pollen wall through which the pollen tube emerges. Classified by shape into pores (porate), furrows (colpate) and combined...
- Colpus (Pl. Colpi)
- An elongated, meridionally oriented furrow in the exine. Grains with three colpi (tricolpate) include most eudicot flowering plants. The colpus can carry...
- NPC Classification
- A three-digit coding system (Number, Position, Character) for pollen apertures devised by Gunnar Erdtman. Allows rapid, reproducible sorting of unknown grains into...
- Spore
- The reproductive unit of ferns, mosses, and fungi. Structurally distinct from pollen (no aperture in the angiosperm sense; trilete or monolete scars...
- Sporopollenin
- The highly chemically inert polymer forming the outer wall (exine) of pollen grains and spores. Resistant to acid, alkali, oxidation, and biological...