Mucilage is a thick, gluey substance produced by nearly all

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

s and some

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s. These microorganisms include

protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

s which use it for their locomotion. The direction of their movement is always opposite to that of the secretion of mucilage. It is a

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates * Polar climate, the c ...

glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...

and an

exopolysaccharide Extracellular polymeric substances (EPSs) are natural polymers of high molecular weight secreted by microorganisms into their environment. EPSs establish the functional and structural integrity of biofilms, and are considered the fundamental comp ...

. Mucilage in plants plays a role in the storage of

water Water (chemical formula ) 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 as a ...

and

food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...

, seed

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

, and thickening membranes. Cacti (and other

succulents 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 conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...

) and

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 ...

seeds are especially rich sources of mucilage.

Occurrence

Exopolysaccharides are the most stabilising factor for microaggregates and are widely distributed in

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

s. Therefore, exopolysaccharide-producing "soil

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

" play a vital role in the

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

of the world's soils. The substance covers the outside of, for example,

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

or filamentous

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

and

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

. Amongst the green algae especially, the group

Volvocales Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae.See the NCBIbr>webpage on Chlamydomonadales Data extracted from the Chlamydomonadales can form planar or ...

are known to produce exopolysaccharides at a certain point in their

life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring * Life-cycle hypothesis ...

. It occurs in almost all plants, but usually in small amounts. It is frequently associated with substances like

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...

s and

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...

s. Mucilage has a unique purpose in some

carnivorous plant Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryot ...

s. The plant

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

Drosera ''Drosera'', which is commonly known as the sundews, is one of the largest genera of carnivorous plants, with at least 194 species. 2 volumes. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginou ...

'' (sundews), ''

Pinguicula ''Pinguicula'', commonly known as the butterworts, is a genus of carnivorous flowering plants in the family Lentibulariaceae. They use sticky, glandular leaves to lure, trap, and digest insects in order to supplement the poor mineral nutrition ...

'', and others have leaves studded with mucilage-secreting glands, and use a " flypaper trap" to capture insects.

Human uses

Mucilage is edible. It is used in

medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pract ...

as it relieves irritation of mucous membranes by forming a protective film. It is known to act as a soluble, or viscous,

dietary fiber Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by the ...

that thickens the fecal mass, an example being the consumption of fiber supplements containing psyllium seed husks. Traditionally,

marshmallow Marshmallow (, ) is a type of confectionery that is typically made from sugar, water and gelatin whipped to a solid-but-soft consistency. It is used as a filling in baking or normally molded into shapes and coated with corn starch. The sugar c ...

s were made from the extract of the mucilaginous root of the

marshmallow plant ''Althaea officinalis'', the marsh mallow or marshmallow, is a species of flowering plant indigenous to Europe, Western Asia and North Africa, which is used in herbalism and as an ornamental plant. A confection made from the root since ancient ...

(''

Althaea officinalis ''Althaea officinalis'', the marsh mallow or marshmallow, is a species of flowering plant indigenous to Europe, Western Asia and North Africa, which is used in herbalism and as an ornamental plant. A confection made from the root since ancient ...

''). The inner bark of the slippery elm (''Ulmus rubra''), a North American tree species, has long been used as a

demulcent A demulcent (derived from the la, demulcere "caress") is a mucilaginous or oleaginous preparation that forms a soothing protective film over a mucous membrane, relieving minor pain and inflammation of the membrane. However, they generally help fo ...

and cough medicine, and is still produced commercially for that purpose. Mucilage mixed with water has been used as a glue, especially for bonding paper items such as labels,

postage stamp A postage stamp is a small piece of paper issued by a post office, postal administration, or other authorized vendors to customers who pay postage (the cost involved in moving, insuring, or registering mail), who then affix the stamp to the fa ...

s, and envelope flaps. Differing types and varying strengths of mucilage can also be used for other adhesive applications, including gluing labels to metal cans, wood to china, and leather to pasteboard. During the fermentation of

nattō , spelled as natto in standard English language use, is a traditional Japanese food made from whole soybeans that have been fermented with ''Bacillus subtilis'' var. ''natto''. It is often served as a breakfast food with rice. It is served wi ...

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...

s, extracellular enzymes produced by the

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

Bacillus natto ''Bacillus subtilis'', known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus ''Bacillu ...

'' react with soybean sugars to produce mucilage. The amount and viscosity of the mucilage are important nattō characteristics, contributing to nattō's unique taste and smell. The mucilage of two kinds of insectivorous plants, sundew (''Drosera'') and butterwort (''Pinguicula''), is used for the traditional production of a variant of the

yoghurt Yogurt (; , from tr, yoğurt, also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as ''yogurt cultures''. Fermentation of sugars in the milk by these bact ...

-like

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

dairy product called

filmjölk (), also known as , is a traditional fermented milk product from Sweden, and a common dairy product within the Nordic countries. It is made by fermenting cow's milk with a variety of bacteria from the species ''Lactococcus lactis'' and ''Leucono ...

Ecological implications for plants

The presence of mucilage in seeds affects important ecological processes in some plant species, such as tolerance of water stress, competition via

allelopathy Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have be ...

, or facilitation of germination through attachment to soil particles. Some authors have also suggested a role of seed mucilage in protecting DNA material from

irradiation Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve ...

damage. The amount of mucilage produced per seed has been shown to vary across the

distribution range Species distribution —or species dispersion — is the manner in which a biological taxon is spatially arranged. The geographic limits of a particular taxon's distribution is its range, often represented as shaded areas on a map. Patterns of ...

of a species, in relation with local environmental conditions of the populations. A variety of

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

grows

aerial roots Aerial roots are roots above the ground. They are almost always adventitious. They are found in diverse plant species, including epiphytes such as orchids (''Orchidaceae''), tropical coastal swamp trees such as mangroves, banyan figs (''Fic ...

that produce a sweet mucus. The Sierra Mixe is a tall variety that survives in poor soils without

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

in Oaxaca, Mexico, and the mucilage has been shown to support

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

through

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

that thrive in its high-

sugar Sugar is the generic name for 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 or double ...

, low-

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

environment.

Plant sources

The following plant and algae species are known to contain far greater concentrations of mucilage than typical: * '' Aloe vera'' * ''

Basella alba ''Basella alba'' is an edible perennial vine in the family Basellaceae. It is found in tropical Asia and Africa where it is widely used as a leaf vegetable. It is native to the Indian subcontinent, Southeast Asia and New Guinea. It is naturali ...

'' (Malabar spinach) *

Cactus A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...

* ''

Chondrus crispus ''Chondrus crispus''—commonly called Irish moss or carrageen moss (Irish ''carraigín'', "little rock")—is a species of red algae which grows abundantly along the rocky parts of the Atlantic coast of Europe and North America. In its fresh ...

'' (Irish moss) * ''

Corchorus ''Corchorus'' is a genus of about 40–100 species of flowering plants in the family Malvaceae, native to tropical and subtropical regions throughout the world. Different common names are used in different contexts, with jute applying to the f ...

'' (jute plant) * ''

Dioscorea polystachya ''Dioscorea polystachya'' or Chinese yam ( zh, s=山药, t=山藥), also called cinnamon-vine, is a species of flowering plant in the yam family. It is sometimes called Chinese potato or by its Korean name ''ma''. It is a perennial climbing vin ...

'' (nagaimo, Chinese yam) * ''

'' (sundews) * ''

Drosophyllum lusitanicum ''Drosophyllum'' ( , rarely ) is a genus of carnivorous plants containing the single species ''Drosophyllum lusitanicum'', commonly known as Portuguese sundew or dewy pine. In appearance, it is similar to the related genus ''Drosera'' (the sun ...

'' * Fenugreek *

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 ...

seeds *

Kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwat ...

Liquorice Liquorice (British English) or licorice (American English) ( ; also ) is the common name of ''Glycyrrhiza glabra'', a flowering plant of the bean family Fabaceae, from the root of which a sweet, aromatic flavouring can be extracted. The liqu ...

root * Mallow *

Marshmallow Marshmallow (, ) is a type of confectionery that is typically made from sugar, water and gelatin whipped to a solid-but-soft consistency. It is used as a filling in baking or normally molded into shapes and coated with corn starch. The sugar c ...

Mullein ''Verbascum'' is a genus of over 450 species of flowering plants, common name mullein (), in the figwort family Scrophulariaceae. They are native to Europe and Asia, with the highest species diversity in the Mediterranean. Mullein or "mullein le ...

Okra Okra or Okro (, ), ''Abelmoschus esculentus'', known in many English-speaking countries as ladies' fingers or ochro, is a flowering plant in the mallow family. It has edible green seed pods. The geographical origin of okra is disputed, with su ...

Nopal Nopal (from the Nahuatl word for the pads of the plant) is a common name in Spanish for ''Opuntia'' cacti (commonly referred to in English as ''prickly pear''), as well as for its pads. There are about 114 known species in Mexico, where it i ...

* ''

Parthenium ''Parthenium'' is a genus of North American shrubs in the tribe Heliantheae within the family Asteraceae and subfamily Asteroideae. The name ''Parthenium'' is an evolution of the Ancient Greek name παρθένιον (''parthenion''), which ref ...

'' * ''

'' (butterwort) * ''

Plantago major ''Plantago major'', the broadleaf plantain, white man's footprint, waybread, or greater plantain, is a species of flowering plant in the plantain family Plantaginaceae. The plant is native to Eurasia. The young, tender leaves can be eaten raw, ...

'' (greater plantain) * ''

Psyllium Psyllium , or ispaghula , is the common name used for several members of the plant genus '' Plantago'' whose seeds are used commercially for the production of mucilage. Psyllium is mainly used as a dietary fiber to relieve symptoms of both const ...

'' seed husks * ''

Salvia hispanica ''Salvia hispanica'', commonly known as chia (), is a species of flowering plant in the mint family, Lamiaceae, native to central and southern Mexico and Guatemala. It is considered a pseudocereal, cultivated for its edible, hydrophilic chia s ...

'' seed (chia) * '' Talinum triangulare'' (waterleaf) *

Taro Taro () (''Colocasia esculenta)'' is a root vegetable. It is the most widely cultivated species of several plants in the family Araceae that are used as vegetables for their corms, leaves, and petioles. Taro corms are a food staple in Africa ...

* ''

Ulmus rubra ''Ulmus rubra'', the slippery elm, is a species of elm native to eastern North America. Other common names include red elm, gray elm, soft elm, moose elm, and Indian elm. Description ''Ulmus rubra'' is a medium-sized deciduous tree with a spre ...

'' bark (slippery elm)

References

External links

Mucilage
McGraw-Hill Encyclopedia of Science and Technology, 5th edition.

Columbia Encyclopedia, Sixth Edition (2007). *{{Cite EB1911, wstitle=Mucilage, volume=18, page=954 Adhesives Carnivorous plants Polysaccharides

Occurrence

Human uses

Ecological implications for plants

Plant sources

See also

References

External links