Pinnae
/ˈpɪniː/
Definition
Pinnae are the primary leaflets or divisions arranged along each side of a central axis in a compound leaf or frond, especially in ferns and some palms. Each pinna is attached to the rachis, the main extension of the leaf stalk. In more finely divided leaves, pinnae may be further divided into smaller segments, which helps distinguish them from simple lobes cut into a single, undivided blade.
Botanical Significance
- Key feature in identification: Their number, spacing, shape, and attachment help botanists tell similar plants apart, especially in ferns and palms where leaf form is a major diagnostic trait.
- Influence on light capture: A divided blade can spread leaf surface through different angles, which may improve light interception and air movement around the leaf.
- Link to leaf development: Their arrangement reflects how a compound or deeply divided leaf formed as it expanded, so they are useful when describing plant morphology and comparing species.
- Clues to variation within a species: Size and outline can vary with age, growing conditions, and position on the plant, which is why identification often uses several leaf characters together rather than one detail alone.
Related Terms
Pinna
Pinna refers to one primary division of a compound leaf or frond, especially in ferns and some palms. It is a distinct…
Rachis
Rachis is the main axis of a compound structure in plants, especially the central stem-like part of a compound leaf or…
Leaflet
Leaflet refers to one of the individual blade-like sections of a compound leaf, where a single leaf is divided into…
Stipe
Stipe refers to a stalk-like supporting structure in certain plants and plant-related organisms. In botany, it most…