Visual Description
Pinnate leaves consist of multiple leaflets attached to a central stalk called the rachis. The arrangement resembles a bird's feather, with leaflets extending from both sides of the rachis.
Types of Pinnate Leaves
Simple Pinnate (Once-Pinnate)
- Leaflets attached directly to the main rachis
- Example: Rose, Ash, Walnut
Bipinnate (Twice-Pinnate)
- Each leaflet is itself divided into smaller leaflets
- Common in tropical trees like Acacias and Jacarandas
- See: Bipinnate
Key Features
- Leaflets: Individual leaf-like structures that make up the compound leaf
- Rachis: The central stem to which leaflets attach
- Terminal leaflet: The leaflet at the tip (if present)
- Lateral leaflets: Leaflets along the sides
Why It Matters
Understanding pinnate leaf structure helps with:
- Tree identification: Many tree families have characteristic pinnate leaves
- Water management: Pinnate leaves can shed excess water efficiently
- Light capture: Multiple leaflets allow flexible positioning for optimal photosynthesis
Examples in Costa Rica
Many Costa Rican trees display pinnate leaves:
- Guanacaste (Enterolobium cyclocarpum): Bipinnate with tiny leaflets
- Mahogany (Swietenia macrophylla): Even-pinnate with 4-6 pairs of leaflets
- Monkey Comb (Pithecellobium dulce): Bipinnate with delicate appearance