The leaves of a Beech tree

A leaf with laminar structure and pinnate venation

Vein skeleton of a leaf

In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For the babyfood see Beech-Nut. Beech ( Fagus) is a genus of ten Species of Deciduous Trees in the Botany, plant science(s, phytology, or plant biology is a branch of Biology and is the scientific study of plant Life Plants are living Organisms belonging to the kingdom Plantae. In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. For this purpose, a leaf is typically flat (laminar) and thin, to expose the cells containing chloroplast to light over a broad area, and to allow light to penetrate fully into the tissues. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Leaves are also the sites in most plants where transpiration and guttation take place. Transpiration is the Evaporation of water from the aerial parts of Plants especially leaves but also stems Flowers and Roots Guttation is the appearance of drops of Xylem sap on the tips or edges of leaves of some Vascular plants such as Grasses At night Transpiration Leaves can store food and water, and are modified in some plants for other purposes. Food is any substance usually composed primarily of Carbohydrates Fats water and/or Proteins that can be eaten or drunk by an Water is a common Chemical substance that is essential for the survival of all known forms of Life. The comparable structures of ferns are correctly referred to as fronds. A fern is any one of a group of about 20000 Species of Plants classified in the phylum or division Pteridophyta, also known as Filicophyta A frond is a large Leaf with many divisions to it and the term is typically used for the leaves of palms Ferns or Cycads A frond is Furthermore, leaves are prominent in the human diet as leaf vegetables. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus This article is primarily about the human diet For a discussion of animal diets see List of feeding behaviours. Leaf vegetables, also called potherbs, greens, or leafy greens, are plant leaves eaten as a Vegetable, sometimes accompanied

Leaf anatomy

A structurally complete leaf of an angiosperm consists of a petiole (leaf stem), a lamina (leaf blade), and stipules (small processes located to either side of the base of the petiole). The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group In Botany, the petiole is the small stalk attaching the Leaf blade to the stem. In Botany, stipule ( Latin stipula: straw stalk is a term coined by Linnaeus The petiole attaches to the stem at a point called the "leaf axil". Not every species produces leaves with all of the aforementioned structural components. In some species, paired stipules are not obvious or are absent altogether. A petiole may be absent, or the blade may not be laminar (flattened). The tremendous variety shown in leaf structure (anatomy) from species to species is presented in detail below under Leaf morphology. After a period of time (i. e. seasonally, during the autumn), deciduous trees shed their leaves. These leaves then decompose into the soil.

A leaf is considered a plant organ and typically consists of the following tissues:

1. An epidermis that covers the upper and lower surfaces
2. An interior chlorenchyma called the mesophyll
3. An arrangement of veins (the vascular tissue).

Epidermis

The epidermis is the outer multi-layered group of cells covering the leaf. The epidermis is the outer single-layered group of cells covering a Plant, especially the Leaf and young tissues of a Vascular plant including stems The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called It forms the boundary separating the plant's inner cells from the external world. The epidermis serves several functions: protection against water loss, regulation of gas exchange, secretion of metabolic compounds, and (in some species) absorption of water. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Most leaves show dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions.

The epidermis is usually transparent (epidermal cells lack chloroplasts) and coated on the outer side with a waxy cuticle that prevents water loss. In Optics, transparency (also called pellucidity) is the Material property of allowing Plant cuticles are a protective waxy covering produced only by the epidermal cells of leaves, young shoots and all other aerial plant organs without Periderm The cuticle is in some cases thinner on the lower epidermis than on the upper epidermis, and is thicker on leaves from dry climates as compared with those from wet climates.

The epidermis tissue includes several differentiated cell types: epidermal cells, guard cells, subsidiary cells, and epidermal hairs (trichomes). Trichomes, from the Greek meaning "growth of Hair " are fine outgrowths or appendages on Plants and certain Protists These are of diverse The epidermal cells are the most numerous, largest, and least specialized. These are typically more elongated in the leaves of monocots than in those of dicots. Monocotyledons or monocots are one of two major groups of Flowering plants (angiosperms that are traditionally recognised the other being Dicotyledons Dicotyledons, or "dicots", is a name for a group of Flowering plants whose Seed typically has two embryonic leaves or Cotyledons There

The epidermis is covered with pores called stomata, part of a stoma complex consisting of a pore surrounded on each side by chloroplast-containing guard cells, and two to four subsidiary cells that lack chloroplasts. In Botany, a stoma (also stomate; plural stomata) is a tiny opening or pore found mostly on the underside of a Plant Leaf The stoma complex regulates the exchange of gases and water vapor between the outside air and the interior of the leaf. Typically, the stomata are more numerous over the abaxial (lower) epidermis than the adaxial (upper) epidermis.

Mesophyll

Most of the interior of the leaf between the upper and lower layers of epidermis is a parenchyma (ground tissue) or chlorenchyma tissue called the mesophyll (Greek for "middle leaf"). Parenchyma is a term used to describe a bulk of a substance It is used in different ways in Animals and in Plants. The types of ground tissue found in Plants develop from ground tissue Meristem and consists of three simple tissues Parenchyma (cells This assimilation tissue is the primary location of photosynthesis in the plant. Assimilation is the process of taking digested food which is circulating the body and then using it to help rebuild cells The products of photosynthesis are called "assimilates".

Fallen leaves at autumn. Autumn (also known as fall in North American English) is one of the four Temperate Seasons Autumn marks the transition from Summer

In ferns and most flowering plants the mesophyll is divided into two layers:

• An upper palisade layer of tightly packed, vertically elongated cells, one to two cells thick, directly beneath the adaxial epidermis. -- Palisade cells are a type of Leaf tissues and can be found within the Mesophyll in leaves of Dicotyledonous plants Its cells contain many more chloroplasts than the spongy layer. These long cylindrical cells are regularly arranged in one to five rows. Cylindrical cells, with the chloroplasts close to the walls of the cell, can take optimal advantage of light. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. The slight separation of the cells provides maximum absorption of carbon dioxide. Absorption, in Chemistry, is a physical or chemical Phenomenon or a process in which Atoms Molecules, or Ions enter some This separation must be minimal to afford capillary action for water distribution. Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it In order to adapt to their different environment (such as sun or shade), plants had to adapt this structure to obtain optimal result. Sun leaves have a multi-layered palisade layer, while shade leaves or older leaves closer to the soil, are single-layered.
• Beneath the palisade layer is the spongy layer. The cells of the spongy layer are more rounded and not so tightly packed. There are large intercellular air spaces. These cells contain fewer chloroplasts than those of the palisade layer.

The pores or stomata of the epidermis open into substomatal chambers, connecting to air spaces between the spongy layer cells.

These two different layers of the mesophyll are absent in many aquatic and marsh plants. Even an epidermis and a mesophyll may be lacking. Instead for their gaseous exchanges they use a homogeneous aerenchyma (thin-walled cells separated by large gas-filled spaces). Aerenchyma is an airy tissue found in Roots of plants which allows exchange of gases between the shoot and the root Their stomata are situated at the upper surface.

Leaves are normally green in color, which comes from chlorophyll found in plastids in the chlorenchyma cells. Green is a Color, the perception of which is evoked by light having a spectrum dominated by energy with a Wavelength of roughly 520–570- nm. Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria. Plastids are major Organelles found in plants and algae Plastids often contain pigments used in photosynthesis and the types of pigments present can change Plants that lack chlorophyll cannot photosynthesize. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.

Autumn Leaves

Fallen autumn leaves

Leaves in temperate, boreal, and seasonally dry zones may be seasonally deciduous (falling off or dying for the inclement season). Botany Autumn leaf color. See --> In Botany and Horticulture, deciduous Plants, including This mechanism to shed leaves is called abscission. Abscission (from Latin abscindere from ab- ‘off away’ + scindere ‘to cut’ is the shedding of a body part After the leaf is shed, a leaf scar develops on the twig. In cold autumns they sometimes change color, and turn yellow, bright orange or red as various accessory pigments (carotenoids and xanthophylls) are revealed when the tree responds to cold and reduced sunlight by curtailing chlorophyll production. Autumn leaf color is a phenomenon that affects the normally Green leaves of many Deciduous Trees and Shrubs by which they take on during Yellow is the Color evoked by light that stimulates both the L and M (long and medium wavelength Cone cells of the Retina about equally The colour orange occurs Red is any of a number of similar Colors evoked by light consisting predominantly of the longest wavelengths of Light discernible by the human eye in the wavelength Carotenoids are organic Pigments that are naturally occurring in Chromoplasts of plants and some other photosynthetic Organisms Xanthophylls (originally phylloxanthins) are yellow Pigments from the Carotenoid group Sunlight, in the broad sense is the total spectrum of the Electromagnetic radiation given off by the Sun. Red anthocyanin pigments are now thought to be produced in the leaf as it dies.

Veins

The veins are the vascular tissue of the leaf and are located in the spongy layer of the mesophyll. This is an article about vascular tissue in plants For transport in animals see Circulatory system. They are typical examples of pattern formation through ramification. The science of pattern formation deals with the visible ( statistically) orderly outcomes of Self-organisation and the common principles behind similar Ramification, in botany is the divergence of the stem and limbs of a Plant into smaller ones i The pattern of the veins is called venation. In Botany, a leaf is an above-ground Plant organ specialized for Photosynthesis.

The veins are made up of:

• xylem, tubes that brings water and minerals from the roots into the leaf. In Vascular plants xylem is one of the two types of transport tissue Phloem being the other
• phloem, tubes that usually moves sap, with dissolved sucrose, produced by photosynthesis in the leaf, out of the leaf. In Vascular plants phloem is the living tissue that carries organic Nutrients (known as photosynthate particularly Sucrose, a sugar to

The xylem typically lies over the phloem. Both are embedded in a dense parenchyma tissue, called "pith", with usually some structural collenchyma tissue present.

Leaf morphology

Underside view of a leaf

External leaf characteristics (such as shape, margin, hairs, etc. ) are important for identifying plant species, and botanists have developed a rich terminology for describing leaf characteristics. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Terminology is the study of terms and their use Terms are Words and Compound words that are used in specific contexts These structures are a part of what makes leaves determinant; they grow and achieve a specific pattern and shape, then stop. Other plant parts like stems or roots are non-determinant, and will usually continue to grow as long as they have the resources to do so.

Classification of leaves can occur through many different designative schema, and the type of leaf is usually characteristic of a species, although some species produce more than one type of leaf. The longest type of leaf is a leaf from palm trees, measuring at nine feet long. The terminology associated with the description of leaf morphology is presented, in illustrated form, at Wikibooks.

Basic leaf types

Leaves of the White Spruce (Picea glauca) are needle-shaped and their arrangement is spiral

• Ferns have fronds. A fern is any one of a group of about 20000 Species of Plants classified in the phylum or division Pteridophyta, also known as Filicophyta A frond is a large Leaf with many divisions to it and the term is typically used for the leaves of palms Ferns or Cycads A frond is
• Conifer leaves are typically needle-, awl-, or scale-shaped
• Angiosperm (flowering plant) leaves: the standard form includes stipules, a petiole, and a lamina. The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group
• Lycophytes have microphyll leaves. The Division Lycopodiophyta (sometimes called Lycophyta) is a tracheophyte subdivision of the Kingdom Plantae It is the oldest extant (living terminology of fossil plants is in places a little confusing In the discipline's 200+ year history certain concepts have become entrenched even though improved understanding has threatened the
• Sheath leaves (type found in most grasses). Monocotyledons or monocots are one of two major groups of Flowering plants (angiosperms that are traditionally recognised the other being Dicotyledons Poaceae or Gramineae is a family in the Class Liliopsida of the flowering plants.
• Other specialized leaves (such as those of Nepenthes)

Arrangement on the stem

Different terms are usually used to describe leaf placement (phyllotaxis):

The leaves on this plant are arranged in pairs opposite one another, with successive pairs at right angles to each other ("decussate") along the red stem. The Nepenthes (nəˈpɛnθiːz from Greek: ne = not penthos = grief sorrow named after the ancient drug Nepenthe) popularly In Botany, phyllotaxis or phyllotaxy is the arrangement of the leaves on the stem of a Plant. Note developing buds in the axils of these leaves.

• Alternate — leaf attachments are singular at nodes, and leaves alternate direction, to a greater or lesser degree, along the stem.
• Opposite — leaf attachments are paired at each node; decussate if, as typical, each successive pair is rotated 90° progressing along the stem; or distichous if not rotated, but two-ranked (in the same geometric flat-plane).
• Whorled — three or more leaves attach at each point or node on the stem. As with opposite leaves, successive whorls may or may not be decussate, rotated by half the angle between the leaves in the whorl (i. e. , successive whorls of three rotated 60°, whorls of four rotated 45°, etc). Opposite leaves may appear whorled near the tip of the stem.
• Rosulate — leaves form a rosette

As a stem grows, leaves tend to appear arranged around the stem in a way that optimizes yield of light. In botany a rosette is a circular arrangement of leaves with all the leaves at a single height In essence, leaves form a helix pattern centred around the stem, either clockwise or counterclockwise, with (depending upon the species) the same angle of divergence. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i A clockwise motion is one that proceeds 'like the Clock 's hands' from the top to the right then down and then to the left and back to the top There is a regularity in these angles and they follow the numbers in a Fibonacci sequence: 1/2, 2/3, 3/5, 5/8, 8/13, 13/21, 21/34, 34/55, 55/89. In Mathematics, the Fibonacci numbers are a Sequence of numbers named after Leonardo of Pisa, known as Fibonacci This series tends to a limit of 360° x 34/89 = 137. 52 or 137° 30', an angle known mathematically as the golden angle. In Geometry, the golden angle is the smaller of the two Angles created by sectioning the circumference of a circle according to the Golden section; that In the series, the numerator indicates the number of complete turns or "gyres" until a leaf arrives at the initial position. Numerator may refer to A numeral used to indicate a count particularly of the equal parts in a fraction For example in 3/4 3 is the numerator The denominator indicates the number of leaves in the arrangement. This can be demonstrated by the following:

• alternate leaves have an angle of 180° (or 1/2)
• 120° (or 1/3) : three leaves in one circle
• 144° (or 2/5) : five leaves in two gyres
• 135° (or 3/8) : eight leaves in three gyres.

The fact that an arrangement of anything in nature can be described by a mathematical formula is not in itself mysterious. Mathematics are the science of discovering numerical relationships and applying formulae to these relationships. Mathematics is the body of Knowledge and Academic discipline that studies such concepts as Quantity, Structure, Space and In Mathematics and in the Sciences a formula (plural formulae, formulæ or formulas) is a concise way of expressing information The formulae themselves can provide clues to the underlying physiological processes that, in this case, determine where the next leaf bud will form in the elongating stem.

Divisions of the lamina (blade)

Two basic forms of leaves can be described considering the way the blade is divided. A simple leaf has an undivided blade. However, the leaf shape may be formed of lobes, but the gaps between lobes do not reach to the main vein. A compound leaf has a fully subdivided blade, each leaflet of the blade separated along a main or secondary vein. A leaflet in Botany is a part of a compound Leaf. A leaflet may resemble an entire leaf but it is not borne on a stem as a leaf is but rather Because each leaflet can appear to be a simple leaf, it is important to recognize where the petiole occurs to identify a compound leaf. Compound leaves are a characteristic of some families of higher plants, such as the Fabaceae. Fabaceae or Leguminosae is a large and economically important family of Flowering plants which is commonly known as the legume family, pea The middle vein of a compound leaf or a frond, when it is present, is called a rachis. A frond is a large Leaf with many divisions to it and the term is typically used for the leaves of palms Ferns or Cycads A frond is Rachis is also the alternate spelling of Ratchis, king of the Lombards 744-749

• Palmately compound leaves have the leaflets radiating from the end of the petiole, like fingers off the palm of a hand, e. g. Cannabis (hemp) and Aesculus (buckeyes). Cannabis ( Cán-na-bis) is a Genus of Flowering plants that includes three putative species Cannabis sativa subsp For the South African Thoroughbred racehorse see Horse Chestnut (horse.
• Pinnately compound leaves have the leaflets arranged along the main or mid-vein.
  • odd pinnate: with a terminal leaflet, e. g. Fraxinus (ash). An ash can be any of four different tree genera from four very distinct families; most commonly in a combined form (e
  • even pinnate: lacking a terminal leaflet, e. g. Swietenia (mahogany). The name mahogany is used when referring to numerous varieties of dark-colored wood originally the wood of the species Swietenia mahagoni, known as West
• Bipinnately compound leaves are twice divided: the leaflets are arranged along a secondary vein that is one of several branching off the rachis. Each leaflet is called a "pinnule". The pinnules on one secondary vein are called "pinna"; e. g. Albizia (silk tree). Albizia is a Genus of about 150 Species of mostly fast-growing Subtropical and Tropical Trees and Shrubs
• trifoliate: a pinnate leaf with just three leaflets, e. g. Trifolium (clover), Laburnum (laburnum). Alsike redirects here Alsike Sweden is also a town in the Knivsta Municipality, Sweden. "Indian laburnum" is the Golden Shower Tree, a distant relative of the genus Laburnum
• pinnatifid: pinnately dissected to the midrib, but with the leaflets not entirely separate, e. g. Polypodium, some Sorbus (whitebeams). Polypodium is a Genus of between 75-100 Species of true Ferns widely distributed throughout the world with the highest species diversity The genus Sorbus is a Genus of about 100–200 species of Trees and Shrubs in the Subfamily Maloideae of the Rose

Characteristics of the petiole

The overgrown petioles of Rhubarb (Rheum rhabarbarum) are edible. Rheum is a genus of Perennial plants that grows from thick short Rhizomes The genus is in the family Polygonaceae, and includes the vegetable

Petiolated leaves have a petiole. In Botany, the petiole is the small stalk attaching the Leaf blade to the stem. Sessile leaves do not: the blade attaches directly to the stem. In clasping or decurrent leaves, the blade partially or wholly surrounds the stem, often giving the impression that the shoot grows through the leaf. When this is actually the case, the leaves are called "perfoliate", such as in Claytonia perfoliata. Claytonia perfoliata ( Miner's lettuce, Winter Purslane, Spring Beauty, or Indian lettuce; syn In peltate leaves, the petiole attaches to the blade inside from the blade margin.

In some Acacia species, such as the Koa Tree (Acacia koa), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes. Acacia is a Genus of Shrubs and Trees belonging to the Subfamily Mimosoideae of the family Fabaceae, first The koa ( Acacia koa; Family Fabaceae) is a large tree endemic to the Hawaiian Islands, primarily Hawai{{okina}}i, Maui In Botany, the petiole is the small stalk attaching the Leaf blade to the stem. There may or may not be normal pinnate leaves at the tip of the phyllode.

A stipule, present on the leaves of many dicotyledons, is an appendage on each side at the base of the petiole resembling a small leaf. In Botany, stipule ( Latin stipula: straw stalk is a term coined by Linnaeus Dicotyledons, or "dicots", is a name for a group of Flowering plants whose Seed typically has two embryonic leaves or Cotyledons There Stipules may be lasting and not be shed (a stipulate leaf, such as in roses and beans), or be shed as the leaf expands, leaving a stipule scar on the twig (an exstipulate leaf). A rose is a perennial flowering Shrub or vine of the Genus Rosa, within the family Rosaceae, that contains over 100 species Bean is a common name for large plant Seeds of several genera of the family Fabaceae (formerly Leguminosae used for human food or animal

• The situation, arrangement, and structure of the stipules is called the "stipulation".
  • free
  • adnate : fused to the petiole base
  • ochreate : provided with ochrea, or sheath-formed stipules, e. In Botany, stipule ( Latin stipula: straw stalk is a term coined by Linnaeus g. rhubarb,
  • encircling the petiole base
  • interpetiolar : between the petioles of two opposite leaves. Rheum is a genus of Perennial plants that grows from thick short Rhizomes The genus is in the family Polygonaceae, and includes the vegetable
  • intrapetiolar : between the petiole and the subtending stem

Venation (arrangement of the veins)

Palmate-veined leaf

Vein skeleton of a Hydrangea leaf

There are two subtypes of venation, namely, craspedodromous, where the major veins stretch up to the margin of the leaf, and camptodromous, when major veins extend close to the margin, but bend before they intersect with the margin.

• Feather-veined, reticulate — the veins arise pinnately from a single mid-vein and subdivide into veinlets. These, in turn, form a complicated network. This type of venation is typical for (but by no means limited to) dicotyledons. Dicotyledons, or "dicots", is a name for a group of Flowering plants whose Seed typically has two embryonic leaves or Cotyledons There
  • Pinnate-netted, penniribbed, penninerved, penniveined; the leaf has usually one main vein (called the mid-vein), with veinlets, smaller veins branching off laterally, usually somewhat parallel to each other; eg Malus (apples). Malus, the apples, is a genus of about 30–35 species of small Deciduous Trees or Shrubs in the family Rosaceae.
  • Three main veins branch at the base of the lamina and run essentially parallel subsequently, as in Ceanothus. Ceanothus L is a Genus of about 50–60 species of Shrubs or small Trees in the buckthorn family Rhamnaceae. A similar pattern (with 3-7 veins) is especially conspicuous in Melastomataceae. The family Melastomataceae (alternatively Melastomaceae) is a taxon of dicotyledonous Flowering plants found mostly in the tropics (two thirds
  • Palmate-netted, palmate-veined, fan-veined; several main veins diverge from near the leaf base where the petiole attaches, and radiate toward the edge of the leaf; e. In Vector calculus, the divergence is an Operator that measures the magnitude of a Vector field &rsquos source or sink at a given point the g. most Acer (maples). Acer ( maple) is a Genus of Trees or Shrubs They are variously classified in a family of their own the Aceraceae, or
• Parallel-veined, parallel-ribbed, parallel-nerved, penniparallel — veins run parallel for the length of the leaf, from the base to the apex. Commissural veins (small veins) connect the major parallel veins. Typical for most monocotyledons, such as grasses. Monocotyledons or monocots are one of two major groups of Flowering plants (angiosperms that are traditionally recognised the other being Dicotyledons Poaceae or Gramineae is a family in the Class Liliopsida of the flowering plants.
• Dichotomous — There are no dominant bundles, with the veins forking regularly by pairs; found in Ginkgo and some pteridophytes. Ginkgo is a genus of highly unusual non-flowering plants with one extant species G A fern is any one of a group of about 20000 Species of Plants classified in the phylum or division Pteridophyta, also known as Filicophyta

Note that although it is the more complex pattern, branching veins appear to be plesiomorphic and in some form were present in ancient seed plants as long as 250 million years ago. Cladistics is the hierarchical classification of Species based on evolutionary ancestry The spermatophytes (from the Greek word "Σπερματόφυτα" (also known as phanerogams) comprise those Plants that produce Seeds They are A pseudo-reticulate venation that is actually a highly modified penniparallel one is an autapomorphy of some Melanthiaceae which are monocots, e. An autapomorphy in Cladistics is a derived trait that is unique to a given terminal group Melanthiaceae is a family of flowering perennial herbs in the Northern Hemisphere. g. Paris quadrifolia (True-lover's Knot). Paris quadrifolia (Herb Paris True-lover's Knot is a species of the genus Paris in the family Melanthiaceae although authorities formerly regarded

Leaf morphology changes within a single plant

• Homoblasty - Characteristic in which a plant has small changes in leaf size, shape, and growth habit between juvenile and adult stages.
• Heteroblasty - Charactistic in which a plant has marked changes in leaf size, shape, and growth habit between juvenile and adult stages.

Leaf terminology

Chart illustrating some leaf morphology terms

Shape

Main article: Leaf shape

Margins (edge)

The leaf margin is characteristic for a genus and aids in determining the species. In Botany, the following terms are used to describe the shape of plant leaves: Acicular ( acicularis) Slender and pointed needle-like

• entire: even; with a smooth margin; without toothing
• ciliate: fringed with hairs
• crenate: wavy-toothed; dentate with rounded teeth, such as Fagus (beech)
• dentate: toothed, such as Castanea (chestnut)
  • coarse-toothed: with large teeth
  • glandular toothed: with teeth that bear glands. For the babyfood see Beech-Nut. Beech ( Fagus) is a genus of ten Species of Deciduous Trees in the Chestnut ( Castanea) (including some chinkapin or Chinquapin) is a Genus of eight or nine Species of Deciduous
• denticulate: finely toothed
• doubly toothed: each tooth bearing smaller teeth, such as Ulmus (elm)
• lobate: indented, with the indentations not reaching to the center, such as many Quercus (oaks)
  • palmately lobed: indented with the indentations reaching to the center, such as Humulus (hop). Elms are Deciduous and Semi-deciduous Trees comprising the genus Ulmus, family Ulmaceae, found The term oak can be used as part of the common name of any of about 400 species of Trees and Shrubs in the Genus Quercus (from Latin The hop ( Humulus) is a small genus of Flowering plants native to the temperate Northern Hemisphere.
• serrate: saw-toothed with asymmetrical teeth pointing forward, such as Urtica (nettle)
• serrulate: finely serrate
• sinuate: with deep, wave-like indentations; coarsely crenate, such as many Rumex (docks)
• spiny: with stiff, sharp points, such as some Ilex (hollies) and Cirsium (thistles). Nettle is the common name for between 30-45 species of Flowering plants of the genus Urtica in the family Urticaceae, with a cosmopolitan though The docks and sorrels, Genus Rumex L, are a genus of about 200 species of annual, biennial and perennial Holly ( Ilex) is a Genus of about 600 Species of Flowering plants in the family Aquifoliaceae, and the only This article is about the plant for other uses see Thistle (disambiguation.

Tip of the leaf

Leaves showing various morphologies. Clockwise from upper left: tripartite lobation, elliptic with serrulate margin, peltate with palmate venation, acuminate odd-pinnate (center), pinnatisect, lobed, elliptic with entire margin

• acuminate: long-pointed, prolonged into a narrow, tapering point in a concave manner.
• acute: ending in a sharp, but not prolonged point
• cuspidate: with a sharp, elongated, rigid tip; tipped with a cusp.
• emarginate: indented, with a shallow notch at the tip.
• mucronate: abruptly tipped with a small short point, as a continuation of the midrib; tipped with a mucro.
• mucronulate: mucronate, but with a smaller spine.
• obcordate: inversely heart-shaped, deeply notched at the top.
• obtuse: rounded or blunt
• truncate: ending abruptly with a flat end, that looks cut off.

Base of the leaf

• acuminate: coming to a sharp, narrow, prolonged point.
• acute: coming to a sharp, but not prolonged point.
• auriculate: ear-shaped
• cordate: heart-shaped with the notch towards the stalk.
• cuneate: wedge-shaped.
• hastate: shaped like an halberd and with the basal lobes pointing outward.
• oblique: slanting.
• reniform: kidney-shaped but rounder and broader than long.
• rounded: curving shape.
• sagittate: shaped like an arrowhead and with the acute basal lobes pointing downward.
• truncate: ending abruptly with a flat end, that looks cut off.

Surface of the leaf

Scale-shaped leaves of a Norfolk Island Pine, Araucaria heterophylla. Araucaria heterophylla (synonym A excelsa) is a distinctive conifer, a member of the ancient and now disjointly distributed family Araucariaceae

The surface of a leaf can be described by several botanical terms:

• farinose: bearing farina; mealy, covered with a waxy, whitish powder.
• glabrous: smooth, not hairy.
• glaucous: with a whitish bloom; covered with a very fine, bluish-white powder.
• glutinous: sticky, viscid.
• papillate, papillose: bearing papillae (minute, nipple-shaped protuberances).
• pubescent: covered with erect hairs (especially soft and short ones)
• punctate: marked with dots; dotted with depressions or with translucent glands or colored dots.
• rugose: deeply wrinkled; with veins clearly visible.
• scurfy: covered with tiny, broad scalelike particles.
• tuberculate: covered with tubercles; covered with warty prominences.
• verrucose: warted, with warty outgrowths.
• viscid, viscous: covered with thick, sticky secretions.

The leaf surface is also host to a large variety of microorganisms; in this context it is referred to as the phyllosphere. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually The phyllosphere is a term used in Microbiology to refer to leaf surfaces or total above-ground surfaces of a plant as a habitat for Microorganisms.

Hairiness (trichomes)

Common Mullein (Verbascum thapsus) leaves are covered in dense, stellate trichomes. Verbascum thapsus ( Great or Common Mullein) is a species of Mullein native to Europe, northern Africa and Asia

Scanning electron microscope image of trichomes on the lower surface of a Coleus blumei [coleus] leaf.

"Hairs" on plants are properly called trichomes. Trichomes, from the Greek meaning "growth of Hair " are fine outgrowths or appendages on Plants and certain Protists These are of diverse Leaves can show several degrees of hairiness. The meaning of several of the following terms can overlap.

• glabrous: no hairs of any kind present.
• arachnoid, arachnose: with many fine, entangled hairs giving a cobwebby appearance.
• barbellate: with finely barbed hairs (barbellae).
• bearded: with long, stiff hairs.
• bristly: with stiff hair-like prickles.
• canescent: hoary with dense grayish-white pubescence.
• ciliate: marginally fringed with short hairs (cilia).
• ciliolate: minutely ciliate.
• floccose: with flocks of soft, woolly hairs, which tend to rub off.
• glandular: with a gland at the tip of the hair.
• hirsute: with rather rough or stiff hairs.
• hispid: with rigid, bristly hairs.
• hispidulous: minutely hispid.
• hoary: with a fine, close grayish-white pubescence.
• lanate, lanose: with woolly hairs.
• pilose: with soft, clearly separated hairs.
• puberulent, puberulous: with fine, minute hairs.
• pubescent: with soft, short and erect hairs.
• scabrous, scabrid: rough to the touch
• sericeous: silky appearance through fine, straight and appressed (lying close and flat) hairs.
• silky: with adpressed, soft and straight pubescence.
• stellate, stelliform: with star-shaped hairs.
• strigose: with appressed, sharp, straight and stiff hairs.
• tomentose: densely pubescent with matted, soft white woolly hairs.
  • cano-tomentose: between canescent and tomentose
  • felted-tomentose: woolly and matted with curly hairs.
• villous: with long and soft hairs, usually curved.
• woolly: with long, soft and tortuous or matted hairs.

Adaptations

Poinsettia bracts are leaves which have evolved red pigmentation in order to attract insects and birds to the central flowers, an adaptive function normally served by petals (which are themselves highly modified leaves). "Christmas Star" redirects here For the Christian tradition see Star of Bethlehem. In Botany, a bract is a modified or specialized Leaf. Bracts are ordinarily associated with reproductive structures (subtending Flowers Inflorescence A petal (from Ancient Greek petalon "leaf" "thin plate" regarded as a highly modified leaf is one member or part of the corolla

In the course of evolution, leaves adapted to different environments in the following ways:

• A certain surface structure avoids moistening by rain and contaminations (Lotus effect). See also Natural environment The '''biophysical''' environment is the symbiosis between the physical environment and the Biological The leaves of the sacred lotus flower ( Nelumbo) are characterized by a very high water repellency ( superhydrophobicity)
• Sliced leaves reduce wind resistance.
• Hairs on the leaf surface trap humidity in dry climates and creates a large boundary layer and reduces water loss.
• Waxy leaf surfaces reduce water loss. Wax has traditionally referred to a substance that is secreted by Bees ( Beeswax) and used by them in constructing their
• Shiny leaves deflect the sun's rays. The Sun (Sol is the Star at the center of the Solar System.
• Reductions of leaf sizes accompanied by a transfer of the photosynthetic functions to the stems reduces water loss.
• In more or less opaque or buried in the soil leaves translucent windows filter the light before the photosynthetis takes place at the inner leaf surfaces (e. g. Fenestraria). Fenestraria is a Monotypic genus of succulent plants in the family Aizoaceae.
• Thicker leaves store water (leaf succulents). Succulent plants, also known as succulents or fat plants, are Water -retaining Plants adapted to Arid climate or Soil conditions
• Aromatic oils, poisons or pheromones produced by leaf borne glands deter herbivores (e. Fragrance oil (s also known as aroma oils, aromatic oils, and flavor oils, are blended synthetic Aroma compounds or natural Essential In the context of Biology, poisons are substances that can cause damage, Illness, or Death to Organisms usually by A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural g. eucalypts). Eucalypts are woody plants belonging to three closely related genera Eucalyptus, Corymbia and Angophora.
• Inclusions of crystalline minerals deters herbivores.
• A transformation into petals attracts pollinators. A petal (from Ancient Greek petalon "leaf" "thin plate" regarded as a highly modified leaf is one member or part of the corolla
• A transformation into spines protects the plants (e. Spines are leaves that have been modified into cylindrical hard structures with sharp ends g. cactus). A cactus (plural cacti) is any member of the Spine plant family Cactaceae, native to the Americas
• A transformation into insect traps helps feeding the plants (carnivorous plants). Carnivorous plants (sometimes called insectivorous plants) are Plants that derive some or most of their Nutrients (but not Energy) from trapping
• A transformation into bulbs helps storing food and water (e. A bulb is an underground vertical Shoot that has modified leaves (or thickened leaf bases that are used as Food Storage organs by g. onion). Organicsalsajpg||thumb|right|Onions used in salsa.]]Cooked onions in frying pan
• A transformation into tendrils allow the plant to climb (e. In Botany, a tendril is a specialized stem, Leaf or petiole with a threadlike shape that is used by Climbing plants for support g. pea). A pea (inaccurately called a '''sweet pea''' by food distubutors is most commonly the small spherical Seed or the seed-pod of the Legume Pisum
• A transformation into bracts and pseudanthia (false flowers) replaces normal flower structures if the true flowers are extremely reduced (e. In Botany, a bract is a modified or specialized Leaf. Bracts are ordinarily associated with reproductive structures (subtending Flowers Inflorescence A pseudanthium (Greek false flower is a special type of Inflorescence, in which several Flowers are grouped together to form a flower-like structure g. Spurges). Euphorbia is a Genus of Plants belonging to the family Euphorbiaceae.

Interactions with other organisms

Leaf insects mimic leaves. The family Phylliidae (often misspelled Phyllidae) contains the extant true leaf insects or walkingleaves, which include some of the most

Although not as nutritious as other organs such as fruit, leaves provide a food source for many organisms. Animals which eat leaves are known as folivores. In Zoology, a folivore is a Herbivore that specializes in eating Leaves. The leaf is one of the most vital parts of the plant, and plants have evolved protection against folivores such as tannins, chemicals which hinder the digestion of proteins and have an unpleasant taste. Tannins are Astringent, bitter plant Polyphenols that either bind and Precipitate or shrink Proteins The astringency from the tannins is what Some animals have cryptic adaptations to avoid their own predators, for example some caterpillars will create a small home in the leaf by folding it over themselves, while other herbivores and their prey mimic the appearance of the leaf. In Ecology, crypsis is the ability of an organism to avoid observation Biological mimicry occurs when a group of organisms the mimics, have Some insects, such as the katydid, take this even further, moving from side to side much like a leaf does in the wind. The family Tettigoniidae, known in American English as katydids and in British English as bush-crickets, contains more than 6400

Bibliography

• Leaves: The formation, charactistics and uses of hundred of leaves in all parts of the world by Ghillean Tolmie Prance. Sir Ghillean Tolmie Prance (born 13 July 1937) is a prominent British botanist and ecologist. 324 photographic plates in black and white, and colour by Kjell B Sandved 256 pages^[1]

Footnotes

See also

• Abscission (losing of leaves)
• Cladophyll
• Guttation (beads of fluid forming at leaf margins)
• Leaf area index
• Phylloclade
• Vernation (sprouting of leaves)
• Evolution of leaves

External links

• VASCULAR PLANT SYSTEMATICS Section B. General Characters and Character States: Position and Arrangement
• Science aid: Leaf Leaf structure and transpiration resource for teens. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. Abscission (from Latin abscindere from ab- ‘off away’ + scindere ‘to cut’ is the shedding of a body part Cladophylls also called cladodes are photosynthetic Branches or portions of a stem that resemble and function as a Leaf, as in the Guttation is the appearance of drops of Xylem sap on the tips or edges of leaves of some Vascular plants such as Grasses At night Transpiration The Leaf Area Index or LAI is the ratio of total upper Leaf surface of Vegetation divided by the Surface area of the land on which the vegetation Phylloclades are flattened photosynthetic short shoots which are modified Branches that greatly resemble or perform the function of Leaves, as in Butcher's Vernation (from vernal, since that is when leaves "spring forth" in Temperate regions is the formation of new leaves or fronds For a more ecological discussion on the evolution of plant morphology refer to Evolutionary history of plants Evolutionary developmental biology (evo-devo