What are Stipules?
Stipules are small structures found at the base where a leaf attaches to the stem. They appear in pairs (one on each side of the leaf) in many plant species.
Types of Stipules
Leaf-like Stipules
- Green and photosynthetic
- Can look like small leaves
- Example: Many Fabaceae (legume) species
Scale-like Stipules
- Small, brown, and dry
- Often fall off early (deciduous)
- Common in many trees
Spine Stipules
- Modified into sharp thorns
- Provide defense
- Example: Acacias and related species
Modified Stipules
- Can become tendrils (climbing plants)
- May form protective sheaths
- Variable across plant families
Stipules in Costa Rican Trees
Legume Family (Fabaceae)
Many Costa Rican legumes like Guanacaste and Guapinol have small stipules at the base of compound leaves. These often fall off as the leaf matures.
Fig Family (Moraceae)
Figs have distinctive stipules that form a protective cap over the developing leaf bud. When the leaf unfolds, the stipule falls off, leaving a characteristic scar around the stem.
Malvaceae Family
Trees like Pochote and Ceiba have stipules that fall off early, leaving scars on the stem.
Why It Matters
- Identification: Stipule type and persistence help identify plant families
- Leaf scars: Fallen stipules leave distinctive marks
- Function: Can protect buds, photosynthesize, or defend against herbivores
- Taxonomy: Presence and type of stipules are important taxonomic characters