botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole). Stipules are considered part of the anatomy of the

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ...

of a typical

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...

, although in many species they may be inconspicuous —or sometimes entirely absent, and the leaf is then termed ''exstipulate''. (In some older botanical writing, the term "stipule" was used more generally to refer to any small leaves or leaf-parts, notably

prophyll In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

s.) The word ''stipule'' was coined by Linnaeus''Concise English Dictionary'' Wordsworth Editions Ltd. 1994, from

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''stipula'', straw, stalk.

Types of stipules

General characteristics

The position of stipules on a plant varies widely from species to species, though they are often located near the base of a leaf. Stipules are most common on dicotyledons, where they appear in pairs alongside each leaf. Some monocotyledon plants display stipule-like structures, but only display one per leaf. A relationship exists between the anatomy of the stem node and the presence or absence of stipules: most plants with ''trilacunar'' nodes have stipules; species with ''unilacunar'' nodes lack stipules. Stipules are morphologically variable and might appear as

gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

s, scales,

hairs Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine ...

, spines, or laminar (leaf-like) structures. If a single stipule goes all the way around the stem, it is known as an ochrea.

Types

According to duration

The three types of stipules according to duration are caducous, deciduous and persistent. Caducous stipules fall off before the leaf unfolds, while deciduous stipules fall off immediately after the leaf unfolds. Persistent stipules remain attached to the plant.

According to shape, size and position

Stipules can be considered free lateral, adnate, interpetiolar, intrapetiolar, ochreate, foliaceous, bud scales, tendrillar or spiny. A stipule can be fused to the stem, or to the other stipule from the same node. A stipule is "adnate" if it's fused together on part of the petiole length, but the anterior is still free. A stipule is "interpetiolar" if it is located in between the petioles, as opposed to being attached to the petioles, and generally one stipule from each leaf is fused together, so it appears that there's just one stipule between each leaf. A stipule is "intrapetiolar" if it is located in the angle that's between a stem and a petiole. In this case, the two stipules generally form together and appear to be one stipule. A stipule is "ochreate" if a single stipule appears to be a solid tube that goes all the way around the stem. A stipule is "foliaceous" if it is leaf-like. These are generally used to photosynthesize. A stipule is considered a "bud scale" if it is hard or scaly and protects leaf buds as they form. These generally fall off as soon as the leaf unfolds. A stipule is considered "tendrillar" if they are long thin tendrils, and are generally used by climbing plants. A stipule is considered "spiny" if they are long and pointy. These are generally used to deter animals. A stipule is considered to be "abaxial", "counter" or "leaf opposed" if it's located on the opposite side to where the leaf meets the stem.

Purpose of stipules

Stipules have various functions. Some stipules are not well understood or may be vestigial. It is known that foliaceous stipules are used like leaves to make energy for the plants. Sometimes stipules protect the next leaf or bud as it grows in then falls off after the leaf unfolds, as with Tulip Poplars. Stipules can be used as climbing tendrils by climbing plants. Spiny stipules can be used to help protect the plant from animals.

References

General references

* Esau, K. 1953. Plant Anatomy. Second Edition. John Wiley & Sons, Inc., New York, London, Sidney. 767 pp.

External links

Stipules and stipels
__NOTOC__ {{Authority control Plant morphology