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A leaf (plural leaves) is the principal lateral appendage of the
vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windpipe' + φυτά ''phutá'' 'plants'), form a large group of plants ( 300,000 a ...
stem Stem or STEM may refer to: Biology * Plant stem '' has lost its leaves, but is producing adventitious roots from the nodes. A stem is one of two main structural axes of a vascular plant, the other being the root In vascular plants, the roo ...

stem
, usually borne above ground and specialized for
photosynthesis File:Photosynthesis equation.svg, upright=1.8, Overall equation for the type of photosynthesis that occurs in plants Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energ ...

photosynthesis
. The leaves, stem, flower and fruit together form the
shoot In botany, shoots consist of plant stem, stems including their appendages, the leaves and lateral buds, flowering stems and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spring, ...

shoot
system. Leaves are collectively referred to as foliage, as in "autumn foliage". In most leaves, the primary
photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's metabolic activities. This chemi ...

photosynthetic
tissue, the
palisade mesophyll Palisade cells are plant cell ''The Plant Cell'' is a monthly peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work ( peers). It functions as a form of self-regulati ...
, is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of ''
Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of Flowering plant, flowering trees, shrubs or Mallee (habit), mallees in the Myrtaceae, myrtle Family (biology), family, Myrtaceae. Along with several other genera in the Tribe (biology), ...

Eucalyptus
'', palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves are flattened and have distinct upper (') and lower (') surfaces that differ in color, hairiness, the number of
stomata File:LeafUndersideWithStomata.jpg, The underside of a leaf. In this species (''Tradescantia zebrina'') the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigme ...

stomata
(pores that intake and output gases), the amount and structure of
epicuticular wax Epicuticular wax is a coating of wax , a typical wax ester. Image:Beeswax foundation.jpg, Commercial honeycomb foundation, made by pressing beeswax between patterned metal rollers. Waxes are a diverse class of organic compounds that are lipophi ...
and other features. Leaves are mostly green in color due to the presence of a compound called
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in the mesosomes of cyanobacteria and in the chloroplast Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll ...
that is essential for photosynthesis as it absorbs light energy from the sun. A leaf with lighter-colored or white patches or edges is called a
variegated leaf '' 'Panascè', a bicolor (yellow-green) common fig cultivar. This Italian cultivar is a ''Chimera (plant), chimera''. Variegation is the appearance of differently coloured zones in the leaves and sometimes the Plant stem, stems and fruit of plant ...
. Leaves can have many different shapes, sizes, and textures. The broad, flat leaves with complex
venation Venation may refer to: * Venation (botany), the arrangement of veins in leaves * Insect wing#Venation, the arrangement of veins in insect wings {{Disambiguation Biology disambiguation pages ...
of
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...

flowering plant
s are known as ''megaphylls'' and the species that bear them, the majority, as broad-leaved or megaphyllous plants, which also includes acrogymnosperms and
ferns A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to tra ...

ferns
. In the lycopods, with different evolutionary origins, the leaves are simple (with only a single vein) and are known as ''microphylls''. Some leaves, such as
bulb In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes k ...
scales, are not above ground. In many aquatic species, the leaves are submerged in water.
Succulent ''. In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil Soil (often stylized as SOiL) is an American rock band that was formed i ...
plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some
cataphyll In plant morphology Phytomorphology is the study of the physical form and external structure of plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other orga ...
s and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Examples include flattened plant stems called
phylloclade Phylloclades and cladodes are flattened, photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be releas ...
s and cladodes, and flattened leaf stems called phyllodes which differ from leaves both in their structure and origin. Some structures of non-vascular plants look and function much like leaves. Examples include the phyllids of
mosses Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Magnoliophyta, also called angiosperms). The biologica ...

mosses
and
liverworts The Marchantiophyta () are a division of non-vascular land plant The Embryophyta () or land plants are the most familiar group of green plants that form vegetation on earth. Embryophyta is a clade within the Phragmoplastophyta, a larger clade ...

liverworts
.


General characteristics

Leaves are the most important organs of most vascular plants. Green plants are
autotrophic An autotroph or primary producer is an organism that produces complex organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bo ...
, meaning that they do not obtain food from other living things but instead create their own food by
photosynthesis File:Photosynthesis equation.svg, upright=1.8, Overall equation for the type of photosynthesis that occurs in plants Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energ ...

photosynthesis
. They capture the energy in
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible spectrum, visible, and ultraviolet light. On Earth, sunlight is light scattering by particles, scattered and attenuation, filtered thr ...

sunlight
and use it to make simple
sugars Sugar is the generic name for Sweetness, sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides o ...
, such as
glucose Glucose is a simple sugar Sugar is the generic name for Sweetness, sweet-tasting, soluble carbohydrates, many of which are used in food. Table sugar, granulated sugar, or regular sugar, refers to sucrose, a disaccharide composed of glucose and ...

glucose
and
sucrose Sucrose is a type of sugar Sugar is the generic name for Sweetness, sweet-tasting, soluble carbohydrates, many of which are used in food. Table sugar, granulated sugar, or regular sugar, refers to sucrose, a disaccharide composed of glucose a ...

sucrose
, from
carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalent bond, covalently double bonded to two oxygen atoms. It occurs naturally in At ...

carbon dioxide
and water. The sugars are then stored as
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose Glucose is a simple sugar with the Chemical formula#Molecular formula, molecular formula . Glucose is the most abundant monosaccharide, a subcategory of carbohydrates ...
, further processed by
chemical synthesis As a topic of chemistry, chemical synthesis (or combination) is the artificial execution of chemical reactions to obtain one or several product (chemistry), products. This occurs by physics, physical and chemical manipulations usually involving on ...
into more complex organic molecules such as
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabol ...

protein
s or
cellulose Cellulose is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ...
, the basic structural material in plant cell walls, or
metabolized Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self-sustaining processes, ...

metabolized
by
cellular respiration 300px, Typical eukaryotic cell Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is a ...

cellular respiration
to provide chemical energy to run cellular processes. The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as
xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Amer ...

xylem
and obtain carbon dioxide from the
atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in ...
by diffusion through openings called
stomata File:LeafUndersideWithStomata.jpg, The underside of a leaf. In this species (''Tradescantia zebrina'') the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigme ...

stomata
in the outer covering layer of the leaf (
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Oth ...
), while leaves are orientated to maximize their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the
plant shoots In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes know ...
and
root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They most often lie bel ...

root
s. Vascular plants transport sucrose in a special tissue called the
phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble Organic chemistry, organic Chemical substance, compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose ...

phloem
. The phloem and xylem are parallel to each other, but the transport of materials is usually in opposite directions. Within the leaf these vascular systems branch (ramify) to form veins which supply as much of the leaf as possible, ensuring that
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
carrying out
photosynthesis File:Photosynthesis equation.svg, upright=1.8, Overall equation for the type of photosynthesis that occurs in plants Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energ ...

photosynthesis
are close to the transportation system. Typically leaves are broad, flat and thin (dorsiventrally flattened), thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the
chloroplast Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules Adenosine triphosphate, ATP and NADPH while fr ...

chloroplast
s, thus promoting photosynthesis. They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance, plants adapted to windy conditions may have pendent leaves, such as in many
willow Willows, also called sallows and osiers, form the genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classific ...

willow
s and
eucalypt Eucalypt is a descriptive name for woody plants with capsule fruiting bodies belonging to seven closely related genera (of the tribe Eucalypteae) found across Australasia: ''Eucalyptus'', ''Corymbia'', ''Angophora'', ''Stockwellia'', ''Allosyncarp ...

eucalypt
s. The flat, or laminar, shape also maximizes
thermal Example of a thermal column between the ground and a cumulus A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by vo ...

thermal
contact with the surrounding
air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together compose about 0.043391% of the atmosphere (0.04402961% at April 2019 concentration ). Number ...
, promoting cooling. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of
transpiration in a tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as a tomato plant. The species originated in western South America South America is a continent entirely in the Western Hemisphere ...

transpiration
, providing the energy required to draw the transpiration stream up from the roots, and
guttation'' Guttation is the exudation of drops of xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water Water is an Inorganic compound, inorgani ...
. Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost. These are interpreted as reduced from megaphyllous leaves of their
Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, ...
ancestors. Some leaf forms are adapted to modulate the amount of light they absorb to avoid or mitigate excessive heat,
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that stud ...

ultraviolet
damage, or desiccation, or to sacrifice light-absorption efficiency in favor of protection from herbivory. For
xerophyteA xerophyte (from Greek ξηρός ''xeros'' dry, φυτόν ''phuton'' plant) is a species of plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms ...

xerophyte
s the major constraint is not light
flux of \mathbf(\mathbf) with the unit normal vector \mathbf(\mathbf) ''(blue arrows)'' at the point \mathbf multiplied by the area dS. The sum of \mathbf\cdot\mathbf dS for each patch on the surface is the flux through the surface Flux describes ...
or
intensity
intensity
, but drought. Some window plants such as ''
Fenestraria ''Fenestraria'' (known as babies' toes or window plant) is a (possibly monotypic In biology, a monotypic taxon is a taxonomic group ( taxon) that contains only one immediately subordinate taxon. A monotypic species In biology, a specie ...
'' species and some ''
Haworthia ''Haworthia'' is a large genus of small succulent plants endemic to Southern Africa Southern Africa is the southernmost region of the African continent A continent is one of several large landmasses. Generally identified by conve ...
'' species such as ''Haworthia tesselata'' and '' Haworthia truncata'' are examples of xerophytes. and ''
Bulbine ''Bulbine'' is a genus of plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy ...
mesembryanthemoides''. Leaves also function to store chemical
energy In physics, energy is the physical quantity, quantitative physical property, property that must be #Energy transfer, transferred to a physical body, body or physical system to perform Work (thermodynamics), work on the body, or to heat it. En ...

energy
and water (especially in
succulents ''. In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes ...

succulents
) and may become specialized organs serving other functions, such as tendrils of
pea The pea is most commonly the small spherical seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction Reproduction (or procreation or breeding) is ...

pea
s and other legumes, the protective spines of cacti and the insect traps in carnivorous plants such as ''
Nepenthes ''Nepenthes'' () is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer ...

Nepenthes
'' and ''Sarracenia''. Leaves are the fundamental structural units from which cones are constructed in gymnosperms (each cone scale is a modified megaphyll leaf known as a sporophyll) and from which flowers are constructed in
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...

flowering plant
s. The internal organization of most kinds of leaves has evolved to maximize exposure of the photosynthetic
organelles In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...
, the
chloroplast Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules Adenosine triphosphate, ATP and NADPH while fr ...

chloroplast
s, to
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
and to increase the absorption of
carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalent bond, covalently double bonded to two oxygen atoms. It occurs naturally in At ...

carbon dioxide
while at the same time controlling water loss. Their surfaces are waterproofed by the
plant cuticle Image:Kale2.jpg, 250px, Water beads on the waxy cuticle of kale leaves A plant cuticle is a protecting film covering the Epidermis (botany), epidermis of leaf, leaves, young shoots and other aerial plant organs without periderm. It consists of lip ...
and gas exchange between the mesophyll cells and the atmosphere is controlled by minute (length and width measured in tens of µm) openings called
stomata File:LeafUndersideWithStomata.jpg, The underside of a leaf. In this species (''Tradescantia zebrina'') the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigme ...

stomata
which open or close to regulate the rate exchange of carbon dioxide,
oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...

oxygen
, and
water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...
into and out of the internal intercellular space system. Stomatal opening is controlled by the
turgor pressure Turgor pressure is the force within the cell that pushes the Cell membrane, plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and defined as the pressure measured by a fluid, measured at a certain point within itsel ...
in a pair of
guard cell Guard cells are specialized plant cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stomatal pore. The stomatal pores are largest when w ...
s that surround the stomatal aperture. In any square centimeter of a plant leaf, there may be from 1,000 to 100,000 stomata. The shape and structure of leaves vary considerably from species to species of plant, depending largely on their adaptation to climate and available light, but also to other factors such as grazing animals (such as deer), available nutrients, and ecological competition from other plants. Considerable changes in leaf type occur within species, too, for example as a plant matures; as a case in point ''Eucalyptus'' species commonly have isobilateral, pendent leaves when mature and dominating their neighbors; however, such trees tend to have erect or horizontal dorsiventral leaves as seedlings, when their growth is limited by the available light. Other factors include the need to balance water loss at high temperature and low humidity against the need to absorb atmospheric carbon dioxide. In most plants, leaves also are the primary organs responsible for
transpiration in a tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as a tomato plant. The species originated in western South America South America is a continent entirely in the Western Hemisphere ...

transpiration
and
guttation'' Guttation is the exudation of drops of xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water Water is an Inorganic compound, inorgani ...
(beads of fluid forming at leaf margins). Leaves can also store
food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, such as carbohydrates, fats, protein (nutrient), proteins, vit ...

food
and
water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts ...

water
, and are modified accordingly to meet these functions, for example in the leaves of succulent plants and in
bulb In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes k ...
scales. The concentration of photosynthetic structures in leaves requires that they be richer in
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabol ...

protein
,
minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (20 ...

minerals
, and
sugars Sugar is the generic name for Sweetness, sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides o ...
than, say, woody stem tissues. Accordingly, leaves are prominent in the
diet Diet may refer to: Food * Diet (nutrition) In nutrition, diet is the sum of food consumed by a person or other organism. The word diet often implies the use of specific intake of nutrition for #Health, health or #Weight management, weight-mana ...
of many
animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, ...
s. Correspondingly, leaves represent heavy investment on the part of the plants bearing them, and their retention or disposition are the subject of elaborate strategies for dealing with pest pressures, seasonal conditions, and protective measures such as the growth of thorns and the production of
phytolith Phytoliths (from Greek language, Greek, "plant stone") are rigid, microscopic structures made of silica, found in some plant tissues and persisting after the decay of the plant. These plants take up silica from the soil, whereupon it is deposited w ...
s,
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood Wood is a porous and fibrous s ...

lignin
s,
tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and Precipitation (chemistry), precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from ...
s and
poison In biology, poisons are substances that can cause death, injury or harm to organs, tissues, cells, and DNA usually by chemical reactions or other activity on the molecular scales, when an organism is exposed to a sufficient quantity. Th ...

poison
s.
Deciduous In the fields of horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists grow flowers, fruits and nuts, vegetables and herbs, as we ...

Deciduous
plants in frigid or cold temperate regions typically shed their leaves in autumn, whereas in areas with a severe dry season, some plants may shed their leaves until the dry season ends. In either case, the shed leaves may be expected to contribute their retained nutrients to the soil where they fall. In contrast, many other non-seasonal plants, such as palms and conifers, retain their leaves for long periods; ''
Welwitschia ''Welwitschia'' is a monotypic taxon, monotypic gymnosperm genus, comprising solely the distinctive ''Welwitschia mirabilis'', Endemism, endemic to the Namib desert within Namibia and Angola. The plant is commonly known simply as welwitschia in En ...

Welwitschia
'' retains its two main leaves throughout a lifetime that may exceed a thousand years. The leaf-like organs of
bryophyte Bryophytes are an informal group consisting of three divisions of non-vascular land plants (embryophyte The Embryophyta () or land plants are the most familiar group of green plants Plants are mainly multicellular organisms, predominantl ...
s (e.g.,
moss Mosses are small, Non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ). Bryophyta is now the formal name for mosses alone, whereas "bryophyte" refers to the informal group of Marchantiophyta, liverw ...

moss
es and
liverworts The Marchantiophyta () are a division of non-vascular land plant The Embryophyta () or land plants are the most familiar group of green plants that form vegetation on earth. Embryophyta is a clade within the Phragmoplastophyta, a larger clade ...
), known as phyllids, differ morphologically from the leaves of
vascular plants Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from the Greek ''trācheia''), form a large group of plants ( 300,000 accepted known species) that are defined as land plants with lignified tissue ...
in that they lack vascular tissue, are usually only a single cell thick, and have no
cuticle A cuticle , or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non-homology (biology), homologous, differing in their ...
stomata or internal system of intercellular spaces. The leaves of bryophytes are only present on the
gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one ...
s, while in contrast the leaves of vascular plants are only present on the sporophytes, and are associated with
buds In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes k ...
(immature shoot systems in the leaf
axils A leaf (plural leaves) is the principal lateral appendage of the vascular plant stem, usually borne above ground and specialized for photosynthesis Photosynthesis is a process used by plants and other organisms to convert light en ...
). These can further develop into either vegetative or reproductive structures. Simple, vascularized leaves (
microphylls In plant anatomy and evolution a microphyll (or lycophyll) is a type of plant leaf with one single, unbranched leaf vein. Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of ...
), such as those of the early
Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, ...
lycopsid ''
Baragwanathia ''Baragwanathia'' is a genus of extinct Lycopodiopsida, lycopsid plants of Late Silurian to Early Devonian age (), fossils of which have been found in Australia, Canada, China and Czechia. The name derives from William Baragwanath who discovered t ...
'', first evolved as enations, extensions of the stem. True leaves or euphylls of larger size and with more complex venation did not become widespread in other groups until the
Devonian period The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, ...
, by which time the carbon dioxide concentration in the atmosphere had dropped significantly. This occurred independently in several separate lineages of vascular plants, in
progymnosperm The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the trimerophytes, and eventually gave rise to the gymnosperms The gymnosperms, also known as Acrogymnospermae, are a group of seed-p ...
s like ''
Archaeopteris ''Archaeopteris'' is an extinct Extinction is the termination of a kind of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life ...

Archaeopteris
'', in Sphenopsida,
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. They differ from mosses and other bryophytes by being vascular, ...

fern
s and later in the
gymnosperms The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes. The term "gymnosperm" comes from the composite word in el, γυμνόσπερμος ( el, γ ...
and
angiosperm The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of land plants, with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species In biology, a species is the ...
s. Euphylls are also referred to as macrophylls or megaphylls (large leaves).


'' leaves with translucent glands A structurally complete leaf of an
angiosperm The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of land plants, with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species In biology, a species is the ...
consists of a petiole (botany), petiole (leaf stalk), a lamina (leaf blade),
stipuleIn botany, a stipule is an outgrowth borne on either side (sometimes just one side) of the base of a leafstalk (the petiole). A pair of stipules is considered part of the anatomy of the leaf A leaf (plural leaves) is the principal lateral ...
s (small structures located to either side of the base of the petiole) and a sheath. Not every species produces leaves with all of these structural components. The proximal stalk or petiole is called a stipe in
ferns A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to tra ...

ferns
. The lamina is the expanded, flat component of the leaf which contains the
chloroplasts Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules Adenosine triphosphate, ATP and NADPH while fr ...
. The sheath is a structure, typically at the base that fully or partially clasps the
stem Stem or STEM may refer to: Biology * Plant stem '' has lost its leaves, but is producing adventitious roots from the nodes. A stem is one of two main structural axes of a vascular plant, the other being the root In vascular plants, the roo ...

stem
above the node, where the latter is attached. Leaf sheathes typically occur in
grasses Poaceae () or Gramineae () is a large and nearly ubiquitous Family (biology), family of monocotyledonous flowering plants known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in l ...

grasses
and
Apiaceae Apiaceae or Umbelliferae is a family of mostly aromatic flowering plants named after the type genus ''Apium'' and commonly known as the celery, carrot or parsley family, or simply as umbellifers. It is the 16th-largest family of flowering plants, ...
(umbellifers). Between the sheath and the lamina, there may be a pseudopetiole, a petiole like structure. Pseudopetioles occur in some
monocotyledons Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds A seed is an Plant embryogenesis, embryonic plant enclosed in a testa (botany), pr ...
including
bananas A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group ...

bananas
, palms and
bamboos
bamboos
. Stipules may be conspicuous (e.g.
beans A bean is the seed of one of several genera Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. T ...
and
roses A rose is a woody perennial flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), families, a ...

roses
), soon falling or otherwise not obvious as in
Moraceae The Moraceae — often called the mulberry family or fig family — are a family of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order( ...

Moraceae
or absent altogether as in the
Magnoliaceae The Magnoliaceae () are a flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), families, approxim ...
. A petiole may be absent (apetiolate), 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
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 ...
. The petiole mechanically links the leaf to the plant and provides the route for transfer of water and sugars to and from the leaf. The lamina is typically the location of the majority of photosynthesis. The upper (
adaxial {{Short pages monitor