stipular

Stipular refers to stipules, which are small appendages located at the base of a leaf stalk (the petiole). Stipules are typically paired at the leaf base, arising from the axis of the leaf, though their presence, size, and persistence vary widely among plant groups. They may be free and separate, or connate with each other or with the stem, and they can form a protective sheath around the developing leaf or shoot in some species.

Stipules exhibit a wide range of forms. They may be foliaceous and leaf-like, scale-like and barely noticeable, or spiny and hairy. In many plants they wither and fall early in development, while in others they persist for a longer period. Some lineages possess large, conspicuous stipules that resemble mini-leaves, whereas in others the stipules are reduced to small markings or scars.

The function of stipules is variable and not always clear. They are commonly thought to protect the developing leaf primordia or bud during early growth. When persistent, stipules can contribute to photosynthesis, shading, or defense, and in certain species they may be modified into structures such as tendrils or extra protective features. The exact role often depends on the plant’s ecology and evolutionary history.

In taxonomy and systematics, the presence, absence, and morphology of stipules can aid in identifying and classifying plants. Stipularity is a characteristic used across many dicot families, though the degree of prominence and persistence is highly diverse. The term stipular derives from Latin stipula, meaning a small stake or point, reflecting the small, often pointed nature of these structures.