Pinnation (also called pennation) is the arrangement of

feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premier ...

-like or multi-divided features arising from both sides of a common

axis An axis (plural ''axes'') is an imaginary line around which an object rotates or is symmetrical. Axis may also refer to: Mathematics * Axis of rotation: see rotation around a fixed axis *Axis (mathematics), a designator for a Cartesian-coordinate ...

. Pinnation occurs in biological

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

, in

crystals A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

, such as some forms of

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...

or metal crystals, and in patterns of

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

or stream beds. The term derives from the Latin word ''pinna'' meaning "feather", "

wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...

", or "

fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...

". A similar concept is "pectination," which is a

comb A comb is a tool consisting of a shaft that holds a row of teeth for pulling through the hair to clean, untangle, or style it. Combs have been used since prehistoric times, having been discovered in very refined forms from settlements dating ba ...

-like arrangement of parts (arising from one side of an axis only). Pinnation is commonly referred to in contrast to "palmation," in which the parts or structures radiate out from a common point. The terms "pinnation" and "pennation" are

cognate In historical linguistics, cognates or lexical cognates are sets of words in different languages that have been inherited in direct descent from an etymology, etymological ancestor in a proto-language, common parent language. Because language c ...

, and although they are sometimes used distinctly, there is no consistent difference in the meaning or usage of the two words.Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928

Plants

Botanically 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 wo ...

, pinnation is an arrangement of discrete structures (such as leaflets,

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

, lobes,

branches A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term ''twig'' usually ...

, or

appendages An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

) arising at multiple points along a common axis. For example, once-divided leaf blades having leaflets arranged on both sides of a

rachis In biology, a rachis (from the grc, ῥάχις [], "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 c ...

are pinnately compound leaves. Many palms (notably the feather palms) and most

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...

s and

grevillea ''Grevillea'', commonly known as spider flowers, is a genus of about 360 species of evergreen flowering plants in the family Proteaceae. Plants in the genus ''Grevillea'' are shrubs, rarely trees, with the leaves arranged alternately along the b ...

s have pinnately divided leaves. Most species of

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s have pinnate or more highly divided

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

s, and in ferns, the leaflets or segments are typically referred to as "pinnae" (singular "pinna"). Plants with pinnate leaves are sometimes colloquially called "feather-leaved". Most of the following definitions are from Jackson's ''Glossary of Botanical Terms'':

Depth of divisions

* pinnatifid and pinnatipartite: leaves with pinnate lobes that are not discrete, remaining sufficiently connected to each other that they are not separate leaflets. * pinnatisect: cut all the way to the midrib or other axis, but with the bases of the pinnae not contracted to form discrete leaflets. * pinnate-pinnatifid: pinnate, with the pinnae being pinnatifid. Leaf morphology division pinnately-lobed.png, Leaf morphology division pinnately-cleft.png, Leaf morphology division pinnately-parted.png, Leaf morphology division pinnately-divided.png, Leaf morphology pinnatisect.png,

Number of divisions

* paripinnate: pinnately compound leaves in which leaflets are borne in pairs along the rachis without a single terminal leaflet; also called "even-pinnate". * imparipinnate: pinnately compound leaves in which there is a lone terminal leaflet rather than a terminal pair of leaflets; also called "odd-pinnate". Leaf morphology even pinnate.png, Leaf morphology odd pinnate.png, Leaf morphology alternipinnada.png,

Iteration of divisions

* bipinnate: pinnately compound leaves in which the leaflets are themselves pinnately compound; also called "twice-pinnate". * tripinnate: pinnately compound leaves in which the leaflets are themselves bipinnate; also called "thrice-pinnate". * tetrapinnate: pinnately compound leaves in which the leaflets are themselves tripinnate. * unipinnate: solitary compound leaf with a row of leaflets arranged along each side of a common

. Leaf morphology bipinnate.png, Leaf morphology type geminate-pinnate.png, Leaf morphology tripinnate.png, The term ''pinnula'' (plural: ''pinnulae'') is the Latin diminutive of ''pinna'' (plural: ''pinnae''); either as such or in the Anglicised form: ''pinnule'', it is differently defined by various authorities. Some apply it to the leaflets of a pinna, especially the leaflets of bipinnate or tripinnate leaves.Chittenden, Fred J. Ed., Royal Horticultural Society Dictionary of Gardening, Oxford 1951 Others also or alternatively apply it to second or third order divisions of a bipinnate or tripinnate leaf.Shastri, Varun. Dictionary of Botany. Publisher: Isha Books 2005. It is the ultimate free division (or leaflet) of a compound leaf, or a pinnate subdivision of a multipinnate leaf.

Animals

In animals, pinnation occurs in various organisms and structures, including: *Some muscles can be unipinnate or

bipinnate muscles Anatomical terminology is used to uniquely describe aspects of skeletal muscle, cardiac muscle, and smooth muscle such as their actions, structure, size, and location. Types There are three types of muscle tissue in the body: skeletal, smooth, ...

*The fish ''

Platax pinnatus ''Platax pinnatus'', also known as the pinnate spadefish, pinnate batfish, pinnatus batfish, dusky batfish, shaded batfish, or red-faced batfish is a fish from the western Pacific that occasionally is kept in marine aquarium A marine aquarium ...

'' is known as the pinnate spadefish or pinnate batfish.

Geomorphology

Pinnation occurs in certain waterway systems in which all major tributary streams enter the main channels by flowing in one direction at an oblique angle.

References

{{Reflist, 3 Plant morphology Leaves sv:Parflikig