In botany

Botany

Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

, a tendril is a specialized stem

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

, leaf

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 or petiole

Petiole (botany)

In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

 with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts. They do not have a lamina or blade, but they can photosynthesize

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

. They can be formed from modified shoots, modified leaves, or auxiliary branches and are sensitive to airborne chemicals, often determining the direction of growth, as in species of Cuscuta

Cuscuta

Cuscuta is a genus of about 100-170 species of yellow, orange or red parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, recent genetic research by the Angiosperm Phylogeny Group has shown that it is correctly placed in the morning glory family, Convolvulaceae...

.

History

The earliest and most comprehensive study of tendrils was Charles Darwin's

Charles Darwin

Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

 monograph On the Movements and Habits of Climbing Plants, which was originally published in 1865. This work also coined the term circumnutation to describe the motion of growing stems and tendrils seeking supports.

Biology of tendrils

In the garden pea, it is only the terminal leaflets that are modified to become tendrils. In other plants such as the yellow vetch (Lathyrus aphaca

Lathyrus aphaca

Lathyrus aphaca is a legume known as the yellow pea or yellow vetch. It is native to southern Europe, parts of Asia, and North Africa. Some consider it to be a weed, particularly when in areas where it is an introduced species, including northern Europe and North America...

) the whole leaf is modified to become tendrils while the stipule

Stipule

In botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk...

s become enlarged and carry out photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

. Still others use the rachis

Rachis

Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...

 of a compound leaf as a tendril, such as members of the genus Clematis

Clematis

Clematis is a genus of about 300 species within the buttercup family Ranunculaceae. Their garden hybrids have been popular among gardeners beginning with Clematis × jackmanii, a garden standby since 1862; more hybrid cultivars are being produced constantly. They are mainly of Chinese and Japanese...

.

The specialised pitcher traps of Nepenthes

Nepenthes

The Nepenthes , popularly known as tropical pitcher plants or monkey cups, are a genus of carnivorous plants in the monotypic family Nepenthaceae. The genus comprises roughly 130 species, numerous natural and many cultivated hybrids...

plants form on the end of tendrils. The tendrils of aerial pitchers are usually coiled in the middle. If the tendril comes into contact with an object for long enough it will usually curl around it, forming a strong anchor point for the pitcher. In this way, the tendrils help to support the growing stem of the plant.