Aperture (botany)

This article is about pollen structure. For stomatal aperture, see Stoma.

Apertures are thin, soft spots on pollen grain walls. When pollen germinates, a tube grows out through these weak spots to carry sperm cells to the egg inside the flower. The apertures are the places where the pollen tube is able to break through the (elsewhere very tough) pollen wall.

The number and configuration of apertures are often very exactly characteristic of different groups of plants. In gymnosperms (cone-bearing plants like pines), pollen typically has one groove-like aperture called a sulcus. Most flowering plants (a group called eudicots, which includes roses, sunflowers, and oak trees) have three furrow-like apertures called colpi that run from one side of the pollen grain to the other, creating what is called tricolpate pollen.

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