Pinna
/ˈpɪnə/
Definition
Pinna refers to one primary division of a compound leaf or frond, especially in ferns and some palms. It is a distinct leaflet-like segment attached along the main axis, called the rachis. In a twice-divided leaf, each pinna may be further divided into smaller units called pinnules. The term helps describe leaf structure and distinguishes these larger side divisions from the whole leaf and from the smaller segments within them.
Function in Plants
- Light capture pattern: In compound leaves and fern fronds, pinna helps spread the blade into smaller sections, which can improve light interception while keeping the overall structure flexible.
- Identification value: The number, shape, spacing, and attachment of pinna are often used to tell species apart, especially in ferns, palms, and other plants with divided leaves.
- Air movement and moisture: A divided outline created by pinna can let more air pass through the leaf or frond, which may reduce physical strain from wind and help surfaces dry after rain.
- Clues for gardeners: Damage, spotting, or browning limited to one pinna can help narrow down a problem's location, while patterns across many pinna may point to broader stress such as drought or nutrient imbalance.
Related Terms
Pinnae
Pinnae are the primary leaflets or divisions arranged along each side of a central axis in a compound leaf or frond…
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…
Sorus
Sorus refers to a cluster of spore-producing structures, most commonly found on the underside or edge of fern fronds…