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What is exine?

Published in Botany 1 min read

Exine is the tough, outer layer of a pollen grain or spore wall. It is primarily composed of sporopollenin, a highly resistant biopolymer.

Here's a breakdown:

  • Definition: Exine constitutes the exterior wall of pollen grains and spores.

  • Composition: The major component of exine is sporopollenin. Sporopollenin is a complex mixture of long-chain fatty acids, phenylpropanoids, phenolics, and small amounts of carotenoids. This unique composition is what gives exine its exceptional durability.

  • Function: Exine's primary function is to protect the pollen grain's genetic material from environmental stressors such as:

    • Desiccation (drying out)
    • UV radiation
    • Microbial attack
    • Mechanical damage
  • Significance: The resistant nature of exine allows pollen grains to be preserved in sedimentary rocks for millions of years. This makes them valuable tools in:

    • Palynology: The study of pollen and spores, which helps in reconstructing past vegetation and climate.
    • Forensic science: Identifying the source of pollen found at crime scenes.
    • Allergy studies: Understanding the types and distribution of allergenic pollen.

In summary, exine is the robust outer layer of pollen grains and spores, composed mainly of sporopollenin, providing crucial protection and serving as a valuable resource in various scientific fields.