HOME

TheInfoList




The ground tissue of plants includes all tissues that are neither
dermal The dermis or corium is a layer of 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. Other cuticle, animal coverings, such a ...
nor
vascular The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an Biological system, organ system that permits blood to circulate and transport nutrien ...
. It can be divided into three types based on the nature of the cell walls. # Parenchyma cells have thin
primary wall A cell wall is a structural layer surrounding some types of cell (biology), cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a ...
s and usually remain alive after they become mature. Parenchyma forms the "filler" tissue in the soft parts of plants, and is usually present in
cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * Adrenal cortex, the portion of the adrenal gland that produces cortisol and ...
,
pericycle The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. Although it is composed of non-vascular parenchyma cells, it's still considered part of the ...
,
pith shoot cut longitudinally to show the broad, solid pith (rough-textured, white) inside the wood (smooth, yellow-tinged). Scale in mm. shoot cut longitudinally to show the chambered pith found in this genus. Scale in mm. Image:Taxus wood.jpg, 250 ...
, and medullary rays in primary
stem Stem or STEM may refer to: Biology * Plant stem, the aboveground structures that have vascular tissue and that support leaves and flowers ** Stipe (botany), a stalk that supports some other structure ** Stipe (mycology), the stem supporting the c ...

stem
and
root In 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 ...

root
. # Collenchyma cells have thin primary walls with some areas of secondary thickening. Collenchyma provides extra mechanical and structural support, particularly in regions of new growth. # Sclerenchyma cells have thick
lignified
lignified
secondary walls and often die when mature. Sclerenchyma provides the main structural support to a plant.


Parenchyma

Parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biolo ...

Parenchyma
is a versatile ground tissue that generally constitutes the "filler" tissue in soft parts of plants. It forms, among other things, the
cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * Adrenal cortex, the portion of the adrenal gland that produces cortisol and ...
(outer region) and
pith shoot cut longitudinally to show the broad, solid pith (rough-textured, white) inside the wood (smooth, yellow-tinged). Scale in mm. shoot cut longitudinally to show the chambered pith found in this genus. Scale in mm. Image:Taxus wood.jpg, 250 ...
(central region) of stems, the cortex of roots, the
mesophyll 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 ...
of leaves, the pulp of fruits, and the
endosperm 350px, right The endosperm is a tissue produced inside the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The ...
of
seeds A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seeds
. Parenchyma cells are often living cells and may remain meristematic at maturity—meaning that they are capable of
cell division Cell division is the process by which a parent cell 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 religiou ...

cell division
if stimulated. They have thin and flexible
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

cellulose
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
s, and are generally polyhedral when close-packed, but can be roughly spherical when isolated from their neighbours. Parenchyma cells are generally large. They have large
central vacuole A vacuole () is a membrane up150px, Schematic of size-based membrane exclusion A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological ...

central vacuole
s, which allow the cells to store and regulate
ions An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...

ions
, waste products, and
water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , even though it provide ...

water
. Tissue specialised for food storage is commonly formed of parenchyma cells. Parenchyma cells have a variety of functions: * In
leaves A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
, they form two layers of
mesophyll 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 ...
cells immediately beneath the epidermis of the leaf, that are responsible for
photosynthesis Photosynthesis is a process used by plants and other organisms to into that, through , can later be released to fuel the organism's activities. Some of this chemical energy is stored in molecules, such as s and es, which are synthesized fro ...

photosynthesis
and the exchange of gases. These layers are called the palisade parenchyma and spongy mesophyll. Palisade parenchyma cells can be either cuboidal or elongated. Parenchyma cells in the
mesophyll 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 ...
of leaves are specialised parenchyma cells called chlorenchyma cells (parenchyma cells with chloroplasts). Parenchyma cells are also found in other parts of the plant. * Storage of starch, protein, fats, oils and water in roots, tubers (e.g.
potatoes The potato is a starch Starch or amylum is a polymeric A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attr ...

potatoes
), seed
endosperm 350px, right The endosperm is a tissue produced inside the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The ...
(e.g.
cereal A cereal is any grass cultivated (grown) for the edible components of its grain A grain is a small, hard, dry seed, with or without an attached husk, hull or fruit layer, harvested for human or animal consumption. A grain crop is a grain-pro ...

cereal
s) and
cotyledon File:Germination-en.svg, 335px, Schematic of epigeal vs hypogeal germination A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one o ...
s (e.g.
pulses A legume () is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, ...
and
peanut The peanut, also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), and as ''Arachis hypogaea'', is a grown mainly for its edible . It is widely grown in the and subtropics, being important to both small and large comme ...

peanut
s) *
Secretion Secretion is the movement of material from one point to another, such as a secreted from a or . In contrast, , is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secret ...
(e.g. the parenchyma cells lining the inside of
resin ducts
resin ducts
) * Wound repair and the potential for renewed meristematic activity * Other specialised functions such as
aeration Aeration (also called aerification or aeriation) is the Systems engineering process, process by which air is circulated through, mixed with or solvation, dissolved in a liquid. Aeration of liquids Methods Aeration of liquids (usually water) is ach ...

aeration
(
aerenchyma alt=Aerenchyma of '' Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma is a spongy tissue that forms spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases ...
) provides buoyancy and helps aquatic plants float. * Chlorenchyma cells carry out photosynthesis and manufacture food. The shape of parenchyma cells varies with their function. In the spongy
mesophyll 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 ...
of a leaf, parenchyma cells range from near-spherical and loosely arranged with large intercellular spaces, to branched or
stellate Stellate, meaning star-shaped, may refer to: * Stellate cell * Stellate ganglion * Stellate reticulum * Stellate veins * Stellate trichomes (hairs) on plants * Stellate laceration or incision Wound#Open * Stellate fan-shaped Espalier (one form of ...

stellate
, mutually interconnected with their neighbours at the ends of their arms to form a three-dimensional network, like in the red kidney bean ''
Phaseolus vulgaris ''Phaseolus vulgaris'', also known as the common bean and French bean, is a herbaceous annual plant grown worldwide for its edible dry seeds or unripe fruit (both commonly called beans). The main categories of common beans, on the basis of use ...

Phaseolus vulgaris
'' and other
mesophyteMesophytes are terrestrial plants 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 ...
s.Jeffree CE, Read N, Smith JAC and Dale JE (1987). Water droplets and ice deposits in leaf intercellular spaces: redistribution of water during cryofixation for scanning electron microscopy. Planta 172, 20-37 These cells, along with the epidermal
guard cell Guard cells are specialized 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 ...
s of the
stoma 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 ...

stoma
, form a system of air spaces and chambers that regulate the exchange of gases. In some works, the cells of the leaf epidermis are regarded as specialised parenchymal cells,Hill, J. Ben; Overholts, Lee O; Popp, Henry W. Grove Jr., Alvin R. Botany. A textbook for colleges. Publisher: MacGraw-Hill 1960 but the modern preference has long been to classify the epidermis as plant dermal tissue, and parenchyma as ground tissue.Evert, Ray F; Eichhorn, Susan E. Esau's Plant Anatomy: Meristems, Cells, and Tissues of the Plant Body: Their Structure, Function, and Development. Publisher: Wiley-Liss 2006. Shapes of parenchyma: * Polyhedral (found in pallisade tissue of the leaf) * Spherical * Stellate (found in stem of plants and have well developed air spaces between them) * Elongated (also found in pallisade tissue of leaf) * Lobed (found in spongy and pallisade mesophyll tissue of some plants)


Collenchyma

Collenchyma tissue is composed of elongated cells with irregularly thickened walls. They provide structural support, particularly in growing
shoot In botany 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 Ancie ...

shoot
s and
leaves A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
. Collenchyma tissue makes up things such as the resilient strands in stalks of
celery Celery (''Apium graveolens'') is a marshland plant in the family that has been cultivated as a since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, leaves or are eaten a ...

celery
. Collenchyma cells are usually living, and have only a thick
primary cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...
made up of cellulose and pectin. Cell wall thickness is strongly affected by mechanical stress upon the plant. The walls of collenchyma in shaken plants (to mimic the effects of wind etc.), may be 40–100% thicker than those not shaken. There are four main types of collenchyma: * Angular collenchyma (thickened at intercellular contact points) * Tangential collenchyma (cells arranged into ordered rows and thickened at the tangential face of the cell wall) * Annular collenchyma (uniformly thickened cell walls) * Lacunar collenchyma (collenchyma with intercellular spaces) Collenchyma cells are most often found adjacent to outer growing tissues such as the
vascular cambium The vascular cambium is the main growth 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 America * ...
and are known for increasing structural support and integrity. The first use of "collenchyma" () was by
Link Link or Links may refer to: Places * Link, West Virginia, an unincorporated community in the US * Link River, Klamath Falls, Oregon, US People with the name * Link (singer) (Lincoln Browder, born 1964), American R&B singer * Link (surname) * ...
(1837) who used it to describe the sticky substance on '' Bletia'' (Orchidaceae) pollen. Complaining about Link's excessive nomenclature,
Schleiden Schleiden is a town in North Rhine-Westphalia, Germany. It lies in the Eifel hills, in the district of Euskirchen (district), Euskirchen, and has 12,998 inhabitants as of 30 June 2017. Schleiden is connected by a tourist railway to Kall, Germany, K ...

Schleiden
(1839) stated mockingly that the term "collenchyma" could have more easily been used to describe elongated sub-epidermal cells with unevenly thickened cell walls.


Sclerenchyma

Sclerenchyma is the tissue which makes the plant hard and stiff. Sclerenchyma is the supporting tissue in
plant Plants are predominantly 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 ...

plant
s. Two types of sclerenchyma cells exist: fibers cellular and
sclereid Sclereids are a reduced form of sclerenchyma The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three types based on the nature of the cell walls. # Parenchyma cells have thin primary ...
s. Their
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
s consist of
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

cellulose
,
hemicellulose A hemicellulose (also known as polyose) is one of a number of heteropolymer, heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all embryophyte, terrestrial plant cell walls.Scheller HV, Ulvskov He ...

hemicellulose
, and
lignin Lignin is a class of complex organic polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its s ...

lignin
. Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation. Sclerenchyma fibers are of great economic importance, since they constitute the source material for many fabrics (e.g.
flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known in Wes ...

flax
,
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa ''Cannabis sativa'' is an annual herbaceous flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embry ...
,
jute Jute is a long, soft, shiny bast fiber epidermis The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infe ...

jute
, and
ramie Ramie (pronounced: , ; from Malay language, Malay ) is a flowering plant in the nettle family Urticaceae, native to eastern Asia. It is a Herbaceous plant, herbaceous perennial plant, perennial growing to tall;
). Unlike the collenchyma, mature sclerenchyma is composed of dead cells with extremely thick cell walls ( secondary walls) that make up to 90% of the whole cell volume. The term ''sclerenchyma'' is derived from the Greek σκληρός (''sklērós''), meaning "hard." It is the hard, thick walls that make sclerenchyma cells important strengthening and supporting elements in plant parts that have ceased elongation. The difference between sclereids is not always clear: transitions do exist, sometimes even within the same plant.


Fibers

Fibers or bast are generally long, slender, so-called prosenchymatous cells, usually occurring in strands or bundles. Such bundles or the totality of a stem's bundles are colloquially called fibers. Their high load-bearing capacity and the ease with which they can be processed has since antiquity made them the source material for a number of things, like
rope A rope is a group of yarns, Plying, plies, fibers or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than simil ...

rope
s,
fabrics A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibre Fiber or fibre (from la, fibra, links=no) is a natural or man-made substance that is signific ...

fabrics
and
mattress A mattress is a large, usually rectangular pad for supporting a lying A lie is an assertion that is believed to be false, typically used with the purpose of deceiving someone. The practice of communicating lies is called lying. A person who ...

mattress
es. The fibers of
flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known in Wes ...

flax
(''Linum usitatissimum'') have been known in
Europe Europe is a continent A continent is any of several large landmass A landmass, or land mass, is a large region In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of scienc ...

Europe
and
Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses. Generally identi ...

Egypt
for more than 3,000 years, those of
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa ''Cannabis sativa'' is an annual herbaceous flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embry ...
(''Cannabis sativa'') in
China China (), officially the People's Republic of China (PRC; ), is a country in East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere ...

China
for just as long. These fibers, and those of
jute Jute is a long, soft, shiny bast fiber epidermis The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infe ...

jute
(''Corchorus capsularis'') and
ramie Ramie (pronounced: , ; from Malay language, Malay ) is a flowering plant in the nettle family Urticaceae, native to eastern Asia. It is a Herbaceous plant, herbaceous perennial plant, perennial growing to tall;
(''Boehmeria nivea'', a
nettle{{redirect, Nettle Nettle is part of the English name of many plants with stinging hairs, particularly those of the genus '' Urtica''. It is also part of the name of plants which resemble ''Urtica'' species in appearance but do not have stinging hai ...
), are extremely soft and elastic and are especially well suited for the processing to
textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, ...

textile
s. Their principal cell wall material is
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

cellulose
. Contrasting are hard fibers that are mostly found in
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...
s. Typical examples are the fiber of many
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 ...
, ''Agave sisalana'' (
sisal Sisal (, ), with the botanical name ''Agave sisalana'', is a species of flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#RED ...

sisal
), ''
Yucca ''Yucca'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their an ...

Yucca
'' or ''
Phormium tenax ''Phormium tenax'' (called flax in New Zealand English New Zealand English (NZE) is the variant of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, e ...
'', '' Musa textilis'' and others. Their cell walls contain, besides cellulose, a high proportion of
lignin Lignin is a class of complex organic polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its s ...

lignin
. The load-bearing capacity of ''Phormium tenax'' is as high as 20–25 kg/mm², the same as that of good
steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
wire (25 kg/ mm²), but the fibre tears as soon as too great a strain is placed upon it, while the wire distorts and does not tear before a strain of 80 kg/mm². The thickening of a cell wall has been studied in ''
Linum ''Linum'' (flax) is a of approximately 200 species''Linum''.
The Jepson Manual.
in t ...
''. Starting at the centre of the fiber, the thickening layers of the secondary wall are deposited one after the other. Growth at both tips of the cell leads to simultaneous elongation. During development the layers of secondary material seem like tubes, of which the outer one is always longer and older than the next. After completion of growth, the missing parts are supplemented, so that the wall is evenly thickened up to the tips of the fibers. Fibers usually originate from meristematic tissues.
Cambium A cambium (plural cambia or cambiums), in plants, is a tissue layer that provides partially undifferentiated cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic ...
and
procambium The meristem is a type of 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 America * ''Triphosa dub ...
are their main centers of production. They are usually associated with the
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 Ame ...

xylem
and
phloem Phloem (, ) is the living 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 America * ''Triphosa d ...

phloem
of the vascular bundles. The fibers of the xylem are always lignified, while those of the phloem are cellulosic. Reliable evidence for the fibre cells' evolutionary origin from
tracheid A tracheid is a long and tapered lignified cell in the xylem Xylem is one of the two types of transport in s, the other being . The basic function of xylem is to transport from roots to stems and leaves, but it also transports . The word ' ...
s exists. During evolution the strength of the tracheid cell walls was enhanced, the ability to conduct water was lost and the size of the pits was reduced. Fibers that do not belong to the xylem are bast (outside the ring of cambium) and such fibers that are arranged in characteristic patterns at different sites of the shoot. The term "sclerenchyma" (originally ''Sclerenchyma'') was introduced by Mettenius in 1865.Mettenius, G. 1865. Über die Hymenophyllaceae. ''Abhandlungen der Mathematisch-Physischen Klasse der Königlich-Sächsischen Gesellschaft der Wissenschaften'' 11: 403-504, pl. 1-5
link


Sclereids

Sclereids are the reduced form of sclerenchyma cells with highly thickened, lignified walls. They are small bundles of sclerenchyma tissue in
plant Plants are predominantly 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 ...

plant
s that form durable layers, such as the cores of
apple An apple is an edible fruit In botany 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 fie ...

apple
s and the gritty texture of
pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species In biology, a species is the basic unit of biological ...

pear
s (''Pyrus communis''). Sclereids are variable in shape. The cells can be isodiametric, prosenchymatic, forked or elaborately branched. They can be grouped into bundles, can form complete tubes located at the periphery or can occur as single cells or small groups of cells within
parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the Ancient G ...

parenchyma
tissues. But compared with most fibres, sclereids are relatively short. Characteristic examples are brachysclereids or the stone cells (called stone cells because of their hardness) of pears and
quince The quince (; ''Cydonia oblonga'') is the sole member of the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of namin ...

quince
s (''Cydonia oblonga'') and those of the shoot of the (''Hoya carnosa''). The cell walls fill nearly all the cell's volume. A layering of the walls and the existence of branched pits is clearly visible. Branched pits such as these are called ramiform pits. The shell of many seeds like those of nuts as well as the stones of
drupe In botany 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 A ...
s like
cherries A cherry is the fruit In botany, a fruit is the seed-bearing structure in flowering plants (also known as angiosperms) formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate seeds. Edible fru ...

cherries
and
plum A plum is a fruit of some species in Prunus subg. Prunus, ''Prunus'' subg. ''Prunus'.'' Mature plum fruits may have a dusty-white waxy coating that gives them a glaucous appearance. This is an epicuticular wax coating and is known as "wax bl ...

plum
s are made up from sclereids. These structures are used to protect other cells.


References


Further reading

* * Moore, Randy; Clark, W. Dennis; and Vodopich, Darrell S. (1998). ''Botany'' (3rd ed.). McGraw-Hill. . * Chrispeels MJ, Sadava DE. (2002) Plants, Genes and Crop Biotechnology. Jones and Bartlett Inc., {{Biological tissue Plant anatomy Plant cells Tissues (biology)