Mucilage is a thick gluey substance produced by nearly all

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s and some

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

s. These microorganisms include

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s which use it for their locomotion, with the direction of their movement always opposite to that of the secretion of mucilage. It is a polar glycoprotein and an exopolysaccharide. Mucilage in plants plays a role in the storage of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

and

food Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...

, 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, ...

, and thickening membranes. Cacti (and other succulents) 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. In 2022, France produced 75% of t ...

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, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

s. Therefore, exopolysaccharide-producing "soil

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

" play a vital role in the

ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...

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

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

and

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

. Amongst the green algae especially, the group Volvocales are known to produce exopolysaccharides at a certain point in their life cycle. 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 Precipitation (chemistry), precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' is widel ...

s and

alkaloid Alkaloids are a broad class of natural product, naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids. Alkaloids are produced by a large varie ...

s. Mucilage has a unique purpose in some carnivorous plants. The plant

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

'' Drosera'' (sundews), '' Pinguicula'' (butterworts), 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 Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

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 (fibre in English in the Commonwealth of Nations, Commonwealth English) 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 co ...

that thickens the fecal mass, an example being the consumption of fiber supplements containing psyllium seed husks. 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 "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 for less than 3 ...

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). Then the stamp is affixed to the f ...

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 is a traditional Japanese cuisine, Japanese food made from whole soybeans that have been Fermentation in food processing, fermented with Bacillus subtilis, ''Bacillus subtilis'' var. ''natto''. It is often served as a breakfast food with rice. ...

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. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

s, extracellular enzymes produced by the

bacterium Bacteria (; : 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 the ...

'' Bacillus natto'' 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

yogurt Yogurt (; , from , ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial Fermentation (food), fermentation of milk. Fermentation of sugars in the milk by these bacteria produces lactic acid, which acts on milk protein to ...

-like Swedish dairy product called

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

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

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

material from irradiation damage. The amount of mucilage produced per seed has been shown to vary across the distribution range of a species, in relation with local environmental conditions of the populations. A variety of

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

grows aerial roots that produce a sweet mucus. The

Sierra Mixe The Sierra Mixe or Mixes District is a district in the east of the Sierra Norte Region of the Mexican state of Oaxaca. It comprises 17 municipalities A municipality is usually a single administrative division having municipal corporation, corp ...

is a tall variety that survives in poor soils without

fertilizer A fertilizer or fertiliser 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 liming materials or other non-nutrient soil amendments. Man ...

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

nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

through

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

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 Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

, low-

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

environment.

Plant sources

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

Aloe vera ''Aloe vera'' () is a succulent plant species of the genus ''Aloe''. It is widely distributed, and is considered an invasive species in many world regions. An evergreen perennial plant, perennial, it originates from the Arabian Peninsula, but ...

'' * '' Watershield'' * Althaea * '' Basella alba'' (Malabar spinach) *

Cactus A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...

* '' Chondrus crispus'' (Irish moss) * '' Corchorus'' (jute plant) * '' Dioscorea polystachya'' (nagaimo, Chinese yam) * '' Drosera'' (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 sund ...

'' * 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. In 2022, France produced 75% of t ...

seeds *

Kelp Kelps are large brown algae or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...

Liquorice Liquorice ( Commonwealth English) or licorice (American English; see spelling differences; ) is the common name of ''Glycyrrhiza glabra'', a flowering plant of the bean family Fabaceae, from the root of which a sweet, aromatic flavouring is ...

root * Mallow * Mullein *

Okra Okra (, ), ''Abelmoschus esculentus'', known in some English-speaking countries as lady's fingers, is a flowering plant in the Malvaceae, mallow family native to East Africa. Cultivated in tropical, subtropical, and warm temperate regions aro ...

* Nopal * '' Parthenium'' * '' Pinguicula'' (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, a ...

'' (greater plantain) * '' Psyllium'' seed husks * '' Salvia hispanica'' seed (chia) * '' Talinum triangulare'' (waterleaf) * Taro * ''

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 sp ...

'' bark (slippery elm)

References

External links