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A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground
plant stem '' has lost its leaves, but is producing adventitious rootsImportant structures in plant development are buds, shoots, root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the pl ...

plant stem
that serves 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 ...
that some plants use to survive winter or other adverse conditions such as summer drought and heat (
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 ...
). The word ''cormous'' usually means plants that grow from corms, parallel to the terms ''tuberous'' and ''bulbous'' to describe plants growing from
tuber Tubers are enlarged structures used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing season, and ...
s and
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
s.


Structure

A corm consists of one or more internodes with at least one growing point, generally with protective leaves modified into skins or
tunics A tunic is a for the body, usually simple in style, reaching from the shoulders to a length somewhere between the hips and the knees. The name derives from the ''tunica,'' the basic garment worn by both men and women in , which in turn was base ...
. The tunic of a corm forms from dead
petiole Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy), the narrow waist of some hymenopteran insects {{disambiguation ...
sheaths—remnants of leaves produced in previous years. They act as a covering, protecting the corm from insects, digging animals, flooding, and water loss. The tunics of some species are thin, dry, and papery, at least in young plants, however, in some families, such as ''Iridaceae'', the tunic of a mature corm can be formidable protection. For example, some of the larger species of ''
WatsoniaWatsonia can refer to: * Watsonia (gastropod), ''Watsonia'' (gastropod), a genus of sea snails in the family Caecidae * Watsonia (plant), ''Watsonia'' (plant), a genus of flowering plants in the iris family * Watsonia (journal), ''Watsonia'' (journa ...
'' accumulate thick, rot-resistant tunics over a period of years, producing a structure of tough, reticulated fibre. Other species, such as many in the genus '' Lapeirousia'', have tunics of hard, woody layers.Dyer, R. Allen, ''The Genera of Southern African Flowering Plants''. , 1975 Internally, a typical corm mostly consists of
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
cells, rich in starch, above a circular basal node from which roots grow. Long-lived cormous plants vary in their long-term development. Some regularly replace their older corms with a stack of younger corms, increased more or less seasonally. By splitting such a stack before the older corm generations wither too badly, the horticulturist can exploit the individual corms for propagation. Other species seldom do anything of that kind; their corms simply grow larger in most seasons. Yet others split when multiple buds 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 on a large corm sprout independently, forming a tussock. Corms can be dug up and used to propagate or redistribute the plant (see, for example,
taro ''Colocasia esculenta'' is a tropical plant grown primarily for its edible corm A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem '' has lost its leaves, but is producing adventitious rootsImportant ...

taro
). Plants with corms generally can be propagated by cutting the corms into sections and replanting. Suitably treated, each section with at least one bud usually can generate a new corm.


Comparison to bulbs

Corms are sometimes confused with true
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
s; they are often similar in appearance to bulbs externally, and thus erroneously called bulbs. Corms are stems that are internally structured with solid tissues, which distinguishes them from bulbs, which are mostly made up of layered fleshy scales that are modified leaves. As a result, a corm cut in half appears solid inside, but a true bulb cut in half reveals that it is made up of layers. Corms are structurally plant stems, with nodes and internodes with buds and produce
adventitiousImportant structures in plant development are buds, 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 upw ...
roots. On the top of the corm, one or a few buds grow into shoots that produce normal leaves and flowers.


Cormels

Corms can form many small cormlets called cormels, from the basal areas of the new growing corms, especially when the main growing point is damaged. These propagate corm-forming plants. A number of species replace corms every year by growing a new corm. This process starts after the shoot develops fully expanded leaves. The new corm forms at the shoot base just above the old corm. As the new corm grows, short
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 appear that end with the newly growing small cormels. As the plants grow and flower, they use up the old corm, which shrivels away. The new corm that replaces the old corm grows in size, especially after flowering ends. The old corm produces the greatest number of cormels when close to the soil surface. Small cormels normally take one or two more years of growth before they are large enough to flower. Cormels do have a reproductive function, but in the wild they also are important as a survival strategy. In most places where
geophytes A storage organ is a part of a 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 ene ...
are common, so are animals that feed on them, whether from above like pigs, or from below like bulb weevils, mole rats, or
pocket gopher Pocket gophers, commonly referred to simply as gophers, are burrowing An Eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal Animals (also called Metazoa) are multicellular ...

pocket gopher
s. Such animals eat through protective tunics, but they generally miss several cormels that remain in the soil to replace the consumed plant. Plants such as '' Homeria'', ''Watsonia'' and ''Gladiolus'', genera that are vulnerable to such animals, are probably the ones that produce cormels in the greatest numbers and most widely distributed over the plant. ''Homeria'' species produce bunches of cormels on underground stem nodes, and ''
Watsonia meriana ''Watsonia meriana'' is a species of flowering plant in the family Iridaceae known by the common name bulbil bugle-lily. It is one of several ''Watsonia'' species known as wild watsonia. It is native to the Cape Provinces of South Africa, but it i ...
'' for example actually produces cormels profusely from under
bract ''). All the "leaves" in this image are bracts. 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 th ...

bract
s on the
inflorescence An inflorescence is a group or cluster of flower A flower, sometimes known as a bloom or blossom Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some ...
s. Those growing from the bottom of the corm are normal fibrous roots formed as the shoots grow, and are produced from the basal area at the bottom of the corm. The second type are thicker layered roots called contractile roots that form as the new corms are growing. They pull the corm deeper into the soil. In some species contractile roots are produced in response to fluctuating soil temperatures and light levels. In such species, once the corm is deep enough within the soil where the temperature is more uniform and there is no light, the contractile roots no longer grow and the corm is no longer pulled deeper into the soil. In some other species, contractile roots seem to be a defence against digging animals and can bury the corm surprisingly deeply over the years. ''Wurmbea marginata'' is one example of a small plant that can be challenging to dig unharmed out of a hard, clayey hillside.


Corms plants

Cultivated plants that form corms include: *
Alismataceae The water-plantains (Alismataceae) 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(biology), orders, 416 Family (bio ...
** ''
Sagittaria ''Sagittaria'' is a genus of about 303. Sagittaria Linnaeus
''
'' spp. (arrowhead or wapatoo) *
Araceae The Araceae 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 territory, typica ...

Araceae
** ''
Alocasia macrorrhizos ''Alocasia macrorrhizos'' is a species of flowering plant in the arum family (Araceae) that it is native to Tropical rainforest, rainforests of Island Southeast Asia, New Guinea, and Queensland and has long been cultivated in the Philippines, many ...

Alocasia macrorrhizos
'' (giant taro) ** ''
Amorphophallus paeoniifolius ''Amorphophallus paeoniifolius'', the elephant foot yam or whitespot giant arum, is a tropical tuber crop grown primarily in Africa, South Asia, Southeast Asia and the tropical Pacific islands. Because of its production potential and popularity ...
'' (elephant foot yam) ** ''
Arisaema '' Arisaema tortuosum'' ''Arisaema'' is a large and diverse genus of the flowering plant family Araceae. The largest concentration of species is in China and Japan, with other species native plant, native to other parts of southern Asia as well ...

Arisaema
'' ** ''
Colocasia esculenta ''Colocasia esculenta'' is a tropical plant grown primarily for its edible corms, a root vegetable most commonly known as taro (), as yam in Malaysia and Singapore, kalo, dasheen, edo, madhumbe, marope, magogoya, patra, arbi or godere. It is t ...

Colocasia esculenta
'' (
taro ''Colocasia esculenta'' is a tropical plant grown primarily for its edible corm A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem '' has lost its leaves, but is producing adventitious rootsImportant ...

taro
) ** ''
Cyrtosperma merkusii ''Cyrtosperma merkusii'' or giant swamp taro, is a crop A crop is a plant or animal product that can be grown and harvested extensively for profit or subsistence. Crops may refer either to the harvested parts or to the harvest in a more refined ...
'' (giant swarm taro) ** ''
Xanthosoma ''Xanthosoma'' is a genus of 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, appro ...
'' spp. (malanga, cocoyam, tannia, and other names) *
Asparagaceae Asparagaceae is a Family (biology), family of flowering plants, placed in the Order (biology), order Asparagales of the monocots. Its best known member is ''Asparagus officinalis'', garden asparagus. Taxonomy In earlier classification systems, ...
** '' Bessera'' ** ''
Brodiaea ''Brodiaea'' , also known by the common name Common may refer to: Places * Common, a townland in County Tyrone, Northern Ireland * Boston Common Boston Common (also known as the Common) is a central public park in downtown Boston, Massachu ...

Brodiaea
'' ** '' Dichelostemma'' ** '' Milla'' ** '' Tecophilaea'' *
Asteraceae The family (biology), family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the Order (biology), order Asterales. Commonly referred to as the aster, daisy, composite, o ...

Asteraceae
** ''
Liatris '' Liatris ligulistylis'' with goldenrod soldier beetles (''Chauliognathus pennsylvanicus'') on it ''Liatris'' () is a genus of flowering plants in the Eupatorieae, boneset tribe within the Asteraceae, sunflower family native to North America (C ...
'' *
Colchicaceae Colchicaceae is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain the w ...
'' ** ''
Colchicum ''Colchicum'' ( or ) 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 r ...

Colchicum
'' *
Cyperaceae The Cyperaceae are a family of graminoid (grass-like), monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank higher than tha ...
** ''
Eleocharis dulcis ''Eleocharis dulcis'', the Chinese water chestnut or water chestnut, is a grass-like sedge The Cyperaceae are a family of graminoid In botany Botany, also called , plant biology or phytology, is the science Science (from ...

Eleocharis dulcis
'' (Chinese water chestnut) *
Iridaceae Iridaceae is a family of plants in order Asparagales Asparagales (asparagoid lilies) is an order (biology), order of plants in modern classification systems such as the Angiosperm Phylogeny Group (APG) and the Angiosperm Phylogeny Web. The o ...

Iridaceae
** ''
Crocosmia ''Crocosmia'' (;), montbretia, is a small 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 ...

Crocosmia
'' ('' Montbretia'') **
Crocus ''Crocus'' (English plural: crocuses or croci) 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 an ...

Crocus
es, including the
saffron Saffron () is a spice derived from the flower of ''Crocus sativus ''Crocus sativus'', commonly known as saffron crocus, or autumn crocus, is a species In biology, a species is the basic unit of biological classification, classifica ...

saffron
crocus (''
Crocus ''Crocus'' (English plural: crocuses or croci) 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 an ...

Crocus
'' spp.) ** '' Dierama'' ** ''
Freesia ''Freesia'' 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 to a ...

Freesia
'' ** ''
Gladiolus ''Gladiolus'' (from Latin, the diminutive of '' gladius'', a sword) is a genus of perennial cormous flowering plants in the iris family (Iridaceae). It is sometimes called the 'sword lily', but is usually called by its generic name (plural ...

Gladiolus
'' ** Some species of ('''' spp.) ** '' Romulea'' *
Musaceae Musaceae is a family (biology), family of flowering plants composed of three genera with ca 91 known species, placed in the Order (biology), order Zingiberales. The family is native to the tropics of Africa and Asia. The plants have a large herbac ...
**
Banana A banana is an elongated, 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 specia ...

Banana
s ('' Musa'' spp.) ** ''
Ensete ''Ensete'' 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 a ...
'' spp. (enset)


See also

*
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
*
Root vegetable Root vegetables are underground plant parts eaten by humans as 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 n ...
*
Tuber Tubers are enlarged structures used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing season, and ...


References

{{botany
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 ...
Garden plants de:Pflanzenknolle he:פקעת