twice-pinnate
Definition
Adjective (Botany): - Describing a compound leaf where the primary leaf axis (rachis) bears secondary axes (pinnae), and leaflets are arranged along these secondary axes. This structure means the leaf is divided two times: first into pinnae, and then each pinna into leaflets.
Usage
- This term is used specifically in botany to describe the architecture of certain leaves, particularly common in ferns and some flowering plants like acacias or mimosas.
- It is a technical descriptor. The simpler, more common term for this structure is "bipinnate."
Examples
Advanced Usage
- Degree of Division: Leaves can be described with greater specificity: "thrice-pinnate" (tripinnate) or "decompound" for multiple divisions.
- Context: The term is primarily used in formal botanical descriptions, field guides, and scientific literature.
Variants and Related Words
- Bipinnate (adj.): The most common synonym for "twice-pinnate."
- Pinna (n.): A primary division of a pinnate leaf.
- Pinnule (n.): A leaflet of a bipinnate leaf; the ultimate division on a twice-pinnate structure.
- Pinnate (adj.): The broader category, describing a feather-like leaf with leaflets arranged along a central axis.
Synonyms
- Bipinnate
Antonyms
- Simple (referring to a leaf with a single, undivided blade).
- Palmate (referring to a leaf with leaflets radiating from a single point, like fingers from a palm).
Noun
-
a pinnate leaf having two pairs of leaflets
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