Stipule
/ˈstɪp.jul/
Definition
Stipule refers to a small leaf-like or scale-like appendage at the base of a leaf stalk, where the leaf joins the stem. It is a plant structure, usually present as a pair, though in some plants it is reduced, fused, or absent. Stipules differ from the leaf blade because they are separate from the main leaf and often protect a developing bud or young leaf.
Function in Plants
- Early leaf protection: In many plants, stipule helps shield a developing leaf or bud while it is still folded or expanding, reducing damage from drying, rubbing, or minor mechanical injury.
- Useful identification feature: Presence, absence, size, and shape of stipule can help botanists separate similar species or families. These details are often checked at the leaf base during plant identification.
- Variation across plant groups: Stipule is common in some groups, such as roses and peas, but absent or very reduced in many others. That pattern makes it a helpful morphological character, meaning a visible structural trait.
- Short-lived or modified forms: In some species, stipule drops early as the leaf matures. In others, it becomes enlarged, leaflike, or spiny, which can change how the plant protects young growth or discourages grazing.
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