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The petiole is a stalk that attaches a leaf to the plant stem. In petiolate leaves the leaf stalk may be long (as in the leaves of
In botany
Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...
, the petiole () is the stalk that attaches the leaf
A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...
blade to the stem
Stem or STEM most commonly refers to:
* Plant stem, a structural axis of a vascular plant
* Stem group
* Science, technology, engineering, and mathematics
Stem or STEM can also refer to:
Language and writing
* Word stem, part of a word respon ...
. It is able to twist the leaf to face the sun, producing a characteristic foliage arrangement (spacing of blades), and also optimizing its exposure to sunlight. Outgrowths appearing on each side of the petiole in some species are called stipule
In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole (botany), petiole). They are primarily found among dicots and rare among monocots. Stipules are considered part ...
s. The terms petiolate and apetiolate are applied respectively to leaves with and without petioles.
Description
The petiole is a stalk that attaches a leaf to the plant stem. In petiolate leaves the leaf stalk may be long (as in the leaves of celery
Celery (''Apium graveolens'' Dulce Group or ''Apium graveolens'' var. ''dulce'') is a cultivated plant belonging to the species ''Apium graveolens'' in the family Apiaceae that has been used as a vegetable since ancient times.
The original wild ...
and rhubarb
Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of ''Rheum'' in the family Polygonaceae, which are cooked and used for food. The plant is a herbaceous perennial that grows from short, thick rhizomes. ...
), or short (for example basil
Basil (, ; , ; ''Ocimum basilicum'' (, )), also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a hardiness (plants), tender plant, and is used in cuisines worldwide. In Western cuisine, the generic term "basil" r ...
). When completely absent, the blade attaches directly to the stem and is said to be sessile or apetiolate. Subpetiolate leaves have an extremely short petiole, and may appear sessile. The broomrape family Orobanchaceae
Orobanchaceae, the broomrapes, is a family (biology), family of mostly parasitic plants of the order (biology), order Lamiales, with about 90 genus, genera and more than 2000 species. Many of these genera (e.g., ''Pedicularis'', ''Rhinanthus'', ...
is an example of a family in which the leaves are always sessile. In some other plant groups, such as the speedwell genus '' Veronica'', petiolate and sessile leaves may occur in different species.
In the grasses (Poaceae
Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...
), the leaves are apetiolate, but the leaf blade may be narrowed at the junction with the leaf sheath to form a pseudopetiole, as in ''Pseudosasa japonica
''Pseudosasa japonica'', the arrow bamboo ( Japanese: metake), is a species of bamboo in the grass family Poaceae native to Japan and Korea, but planted worldwide as a horticultural plant.
Description
This vigorous bamboo forms thickets up to ...
''.
In plants with compound leaves
A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, fl ...
, the leaflets are attached to a continuation of the petiole called the rachis
In biology, a rachis (from the [], "backbone, spine") is a main axis or "shaft".
In zoology and microbiology
In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the ''rachi ...
. Each leaflet may be attached to the rachis by a short stalk called the petiolule. There may be swollen regions at either end of the petiole known as pulvina (singular = pulvinus
A pulvinus (pl. ''pulvini'') may refer to a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. Pulvinus is also a botanical term for the persistent peg-like bases of the leaves in the conif ...
) that are composed of a flexible tissue that allows leaf movement. Pulvina are common in the bean family Fabaceae
Fabaceae () or Leguminosae,International Code of Nomen ...
and the prayer plant family Marantaceae
The Marantaceae are a family, the arrowroot family, or the prayer plant family, of flowering plants consisting of 31 genera and around 530 species, defining it as one of the most species-rich families in its order. Kennedy, H. (2000). “Diversif ...
. A pulvinus on a petiolule is called a pulvinulus.
In some plants, the petioles are flattened and widened to become phyllodes (also known as phyllodia or cladophylls) and the true leaves may be reduced or absent. Thus, the phyllode comes to serve the functions of the leaf. Phyllodes are common in the genus ''Acacia
''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa, South America, and Austral ...
'', especially the Australian species, at one time put in ''Acacia'' subgenus ''Phyllodineae''.
In ''Acacia koa
''Acacia koa'', commonly known as koa, is a species of Flowering plant, flowering tree in the Family (biology), family Fabaceae. It is Endemism, endemic to the Hawaiian Islands, where it is the second most common tree. The highest populations ar ...
'', the phyllodes are leathery and thick, allowing the tree to survive stressful environments. The petiole allows partially submerged hydrophyte
Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquat ...
s to have leaves floating at different depths, the petiole being between the node and the stem.
In plants such as rhubarb (''Rheum rhabarbarum
''Rheum rhabarbarum'' is a species of flowering plant in the family Polygonaceae, native to a region stretching from southern Siberia to north and central China. It has been harvested from the wild for centuries for its root, which was harvested ...
''), celery (''Apium graveolens
''Apium graveolens'', known in English as wild celery,Streeter D, Hart-Davies C, Hardcastle A, Cole F, Harper L. 2009. ''Collins Flower Guide''. Harper Collins is an Old World species of flowering plant in the family Apiaceae. It was first desc ...
''), artichokes
The artichoke (''Cynara cardunculus'' var. ''scolymus''),Rottenberg, A., and D. Zohary, 1996: "The wild ancestry of the cultivated artichoke." Genet. Res. Crop Evol. 43, 53–58. also known by the other names: French artichoke, globe artichoke, ...
, and cardoons (''Cynara cardunculus''), the petioles ('stalks' or 'ribs') are cultivated as edible crops. The petiole of rhubarb grows directly from the rhizome
In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...
and produces the leaf at its end. Botanically, it is categorized as a vegetable but, culinarily, it is more often used as a fruit.
Longest
The longest known petiole is that of the royal waterlily or iaupê jaçanã ''Victoria amazonica
''Victoria amazonica'' is a species of flowering plant, the second largest in the water lily family Nymphaeaceae. It is called Vitória-Régia or Iaupê-Jaçanã ("the Jacanidae, jacana's waterlily") in Brazil and Atun Sisac ("great flower") in ...
'' which is up to in length.
Etymology
'Petiole' comes fromLatin
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
petiolus, or 'little foot', 'stem', an alternative diminutive
A diminutive is a word obtained by modifying a root word to convey a slighter degree of its root meaning, either to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment, and sometimes to belittle s ...
of 'pes', 'foot'. The regular diminutive 'pediculus' is also used for 'foot stalk'.
See also
*Hyponastic response
In plant biology, the hyponastic response is a nastic movement characterized by an upward bending of leaves or other plant parts, resulting from accelerated growth of the lower side of the petiole in comparison to its upper part. This can be o ...
*Pedicel
Pedicle or pedicel may refer to:
Human anatomy
*Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures
...
References
External links
* {{DEFAULTSORT:Petiole (Botany) Leaf morphology de:Blatt (Pflanze)#Blattstiel he:פטוטרת fi:Lehtiruoti