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Tubers are enlarged structures used as
storage organ A storage organ is a part of 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 fung ...
s for
nutrient A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and t ...
s in some
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. They are used for the plant's
perennationIn 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 knowle ...
(survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing season, and as a means of
asexual reproduction Asexual reproduction is a type of that does not involve the fusion of s or change in the number of . The offspring that arise by asexual reproduction from either unicellular or s inherit the full set of genes of their single parent. Asexual rep ...
. ''Stem tubers'' form thickened
rhizome 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 ...

rhizome
s (underground stems) or
stolon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...
s (horizontal connections between organisms); well known species with stem tubers include the
potato The potato is a starch#Food, starchy tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae. Wild potato species can be found thro ...

potato
and yam. Some writers also treat modified lateral
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
s (''root tubers'') under the definition; these are found in
sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledon The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plant The flowering plants, also known as Angio ...

sweet potato
es,
cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names) is a woody shrub A shrub (or bush, but this is more of a gardening term) is a small- to medium-sized perennial woody plant. Unlike herb ...

cassava
, and
dahlia Dahlia ( or ) 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 the ...

dahlia
s.


Terminology

The term originates from the
Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an appa ...

Latin
, meaning "lump, bump, swelling". Some writers define the term "tuber" to mean only structures derived from
stems
stems
; others use the term for structures derived from stems or
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
s., p. 124


Stem tubers

A stem tuber forms from thickened
rhizome 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 ...

rhizome
s or
stolon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...
s. The top sides of the tuber produce shoots that grow into typical stems and leaves and the undersides produce roots. They tend to form at the sides of the parent plant and are most often located near the soil surface. The underground tuber is normally a short-lived storage and regenerative organ developing from a shoot that branches off a mature plant. The offspring or new tubers are attached to a parent tuber or form at the end of a hypogeogenous (initiated below ground) rhizome. In the autumn the plant dies, except for the new offspring tubers, which have one dominant bud that in spring regrows a new shoot producing stems and leaves; in summer the tubers decay and new tubers begin to grow. Some plants also form smaller tubers and/or
tubercule Image:Mammillaria marksiana.jpg, 250px, This view of the cactus ''Mammillaria marksiana'' shows its pattern of prominent tubercles, with the spines emanating from each tubercle's tip. In anatomy, a tubercle (literally 'small tuber', Latin for 'lum ...
s that act like seeds, producing small plants that resemble (in morphology and size) seedlings. Some stem tubers are long-lived, such as those of tuberous
begonia ''Begonia'' is a genus of perennial flowering plants in the family Begoniaceae. The genus contains more than 1,800 different plant species. The Begonias are native to moist subtropical and tropical climates. Some species are commonly grown indo ...

begonia
s, but many plants have tubers that survive only until the plants have fully leafed out, at which point the tuber is reduced to a shriveled-up husk. Stem tubers generally start off as enlargements of the
hypocotyl Diagram of Scouler's willow (''Salix scouleriana'') seed, indicating position of hypocotyl. The hypocotyl (short for "hypocotyledonous stem", meaning "below seed leaf") is the stem of a germinating seedling A seedling is a young sporophyte ...
section of a seedling, but sometimes also include the first node or two of the
epicotylAn epicotyl is important for the beginning stages of a plant's life. It is the region of a seedling stem above the stalks of the seed leaves of an embryo plant. It grows rapidly, showing hypogeal germination, and extends the stem above the soil surfa ...
and the upper section of the root. The tuber has a vertical orientation, with one or a few vegetative buds on the top and fibrous roots produced on the bottom from a basal section. Typically the tuber has an oblong rounded shape. Tuberous begonias, yams, and cyclamens are commonly grown stem tubers. Mignonette vine (''
Anredera cordifolia ''Anredera cordifolia'', commonly known as the Madeira-vine or mignonette vine, is a South American species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as ...
'') produces aerial stem tubers on vines; the tubers fall to the ground and grow. ''
Plectranthus esculentus ''Coleus esculentus'', synonym A synonym is a word, morpheme A morpheme is the smallest meaningful lexical item in a language. A morpheme is not a word. The difference between a morpheme and a word is that a morpheme bound and free morpheme ...
'', of the mint family
Lamiaceae The Lamiaceae ( ) or Labiatae are a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social ter ...

Lamiaceae
, produces tuberous underground organs from the base of the stem, weighing up to per tuber, forming from axillary buds producing short stolons that grow into tubers. Even though
legume A legume () is a 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 ...

legume
s are not commonly associated with forming stem tubers, ''
Lathyrus tuberosus ''Lathyrus tuberosus'' (also known as the tuberous pea, tuberous vetchling, earthnut pea, aardaker, or tine-tare) is a small, climbing Climbing is the activity of using one's hands, feet, or any other part of the body to ascend a steep to ...

Lathyrus tuberosus
'' is an example native to Asia and Europe, where it was once grown as a crop.


Potatoes

Potatoes are stem tubersenlarged stolons thicken to develop into
storage organ A storage organ is a part of 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 fung ...
s. The tuber has all the parts of a normal stem, including nodes and internodes. The nodes are the eyes and each has a leaf scar. The nodes or eyes are arranged around the tuber in a spiral fashion beginning on the end opposite the attachment point to the stolon. The terminal bud is produced at the farthest point away from the stolon attachment and tubers, and thus show the same
apical dominance show particularly strong apical dominance, strongest of all being in the family Araucariaceae Araucariaceae – also known as araucarians – is a very ancient family of coniferous trees. The family achieved its maximum diversity during the Juras ...
as a normal stem. Internally, a tuber is filled with starch stored in enlarged
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
-like cells. The inside of a tuber has the typical cell structures of any stem, including a pith, vascular zones, and a cortex. The tuber is produced in one growing season and used to perennate the plant and as a means of propagation. When fall comes, the above-ground structure of the plant dies, but the tubers survive underground over winter until spring, when they regenerate new shoots that use the stored food in the tuber to grow. As the main shoot develops from the tuber, the base of the shoot close to the tuber produces adventitious roots and lateral buds on the shoot. The shoot also produces stolons that are long etiolated stems. The stolon elongates during long days with the presence of high
auxins Auxins (plural of auxin ) are a class of plant hormone Plant hormones (also known as phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and ...
levels that prevent root growth off of the stolon. Before new tuber formation begins, the stolon must be a certain age. The enzyme lipoxygenase makes a hormone,
jasmonic acid Jasmonic acid (JA) is an organic compound found in several plants including jasmine. The molecule is a member of the jasmonate class of plant hormones. It is biosynthesized from linolenic acid by the octadecanoid pathway. It was first isolated ...

jasmonic acid
, which is involved in the control of potato tuber development. The stolons are easily recognized when potato plants are grown from seeds. As the plants grow, stolons are produced around the soil surface from the nodes. The tubers form close to the soil surface and sometimes even on top of the ground. When potatoes are cultivated, the tubers are cut into pieces and planted much deeper into the soil. Planting the pieces deeper creates more area for the plants to generate the tubers and their size increases. The pieces sprout shoots that grow to the surface. These shoots are rhizome-like and generate short stolons from the nodes while in the ground. When the shoots reach the soil surface, they produce roots and shoots that grow into the green plant.


Root tubers

A tuberous root or storage root is a modified lateral
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
, enlarged to function as a
storage organ A storage organ is a part of 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 fung ...
. The enlarged area of the tuber can be produced at the end or middle of a root or involve the entire root. It is thus different in origin, but similar in function and appearance, to a stem tuber. Plants with tuberous roots include the
sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledon The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plant The flowering plants, also known as Angio ...

sweet potato
(''Ipomoea batatas''),
cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names) is a woody shrub A shrub (or bush, but this is more of a gardening term) is a small- to medium-sized perennial woody plant. Unlike herb ...

cassava
, and
dahlia Dahlia ( or ) 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 the ...

dahlia
. Root tubers are
perennating organ A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...
s, thickened roots that store nutrients over periods when the plant cannot actively grow, thus permitting survival from one year to the next. The massive enlargement of secondary roots typically represented by sweet potato have the internal and external cell and tissue structures of a normal root; they produce
adventitious roots Important structures in plant development are buds 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 specialise ...

adventitious roots
and stems, which again produce adventitious roots. In root tubers, there are no nodes and internodes or reduced leaves. The proximal end of the tuber, which was attached to the old plant, has crown tissue that produces buds which grow into new stems and foliage. The distal end of the tuber normally produces unmodified roots. In stem tubers the order is reversed, with the distal end producing stems. Tuberous roots are biennial in duration: the plant produces tubers the first year, and at the end of the growing season, the shoots often die, leaving the newly generated tubers; the next growing season, the tubers produce new shoots. As the shoots of the new plant grow, the stored reserves of the tuber are consumed in the production of new roots, stems, and reproductive organs; any remaining root tissue dies concurrently to the plant's regeneration of the next generation of tubers. The ''
Hemerocallis fulva ''Hemerocallis fulva'', the orange day-lily, tawny daylily, corn lily, tiger daylily, fulvous daylily or ditch lily (also railroad daylily, roadside daylily, outhouse lily, and wash-house lily), is a species of daylily native to Asia. It is very ...

Hemerocallis fulva
''
daylily A daylily or day lily is a flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anyt ...

daylily
and a number of daylily hybrids have large root tubers; ''H. fulva'' spreads by underground stolons that end with a new fan that grows roots that produce thick tubers and then send out more stolons.http://sain.utk.edu/invasives/species32.shtml Root tubers, along with other storage tissues that plants produce, are consumed by animals as a rich source of nutrients. The root tubers of arrowhead plants of the genus ''
Sagittaria ''Sagittaria'' is a genus of about 303. Sagittaria Linnaeus
''
'' are eaten by ducks. Plants with root tubers are propagated in late summer to late winter by digging up the tubers and separating them, making sure that each piece has some crown tissue for replanting.


See also

*
Bulb 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 ...

Bulb
, modified stems with a short fleshy vertical stem, covered by thick fleshy modified leaves that enclose a bud for the next season's growth *
Caudex A caudex (plural: caudices) of a plant is a , but the term is also used to mean a and particularly a basal stem structure from which new growth arises.pages 456 and 695 In the strict sense of the term, meaning a stem, "caudex" is most often use ...
, a form of stem modification similar in appearance to a tuber *
Corm A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word '' ...

Corm
, modified stems covered by dry scale-like leaves called a tunic, differing from true bulbs by having distinct nodes and internodes *
Taproot A taproot is a large, central, and dominant 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 ...
, the largest, most central, and most dominant root of some plants


References


External links

{{commons category, Tubers
Cook's Thesaurus
has a good inventory of tuber varieties.
CGIAR Research Program on Roots, Tubers and Bananas
Plant morphology ''Plant morphology'' is the field in botany that studies the diversity in forms, with the naked eye or slight optical magnification. This is opposed to plant anatomy (see :Plant anatomy) that needs to cut into plants to be able to study its subject, ...
Plant reproduction {{Commons cat, Plant reproduction Plants, reproduction Horticultural techniques Reproduction, .Plant ...
Plant anatomy *