Legume

Legumes(/ˈlɛɡjuːm,ləˈɡjuːm/) are plants in the familyFabaceae(or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also calledpulses. Legumes are grown agriculturally, primarily for human consumption, but also as livestock forage andsilage, and as soil-enhancinggreen manure. Well-known legumes includebeans,chickpeas,peanuts,lentils,lupins,mesquite,carob,tamarind,alfalfa, andclover. Legumes produce a botanically unique type offruit– asimpledry fruitthat develops from a simplecarpeland usuallydehisces(opens along a seam) on two sides.
Most legumes havesymbioticnitrogen-fixingbacteria,Rhizobia, in structures calledroot nodules. Some of the fixed nitrogen becomes available to later crops, so legumes play a key role incrop rotation.
The termpulse, as used by the United Nations'Food and Agriculture Organization(FAO), is reserved for legume crops harvested solely for the dry seed.This excludesgreen beansandgreen peas, which are consideredvegetablecrops. Also excluded are seeds that are mainly grown for oil extraction (oilseedslikesoybeansandpeanuts),and seeds which are used exclusively for sowingforage(clovers,alfalfa).However, in common usage, these distinctions are not always clearly made, and many of the varieties used for dried pulses are also used for green vegetables, with their beans in pods while young.
Some Fabaceae, such asScotch broomand otherGenisteae, are leguminous but are usually not called legumes by farmers, who tend to restrict that term to food crops.
The FAO recognizes 11 primary pulses, excluding green vegetable legumes (e.g. green peas) and legumes used mainly for oil extraction (e.g., soybeans and groundnuts) or used only as seed (e.g., clover and alfalfa).
Legumes are widely distributed as the third-largestland plantfamily in terms of number of species, behind only theOrchidaceaeandAsteraceae, with about 751generaand some 19,000 known species,constituting about seven percent of flowering plant species.
Many legumes containsymbioticbacteria calledRhizobiawithinroot nodulesof theirroot systems(plants belonging to the genusStyphnolobiumare one exception to this rule). These bacteria have the special ability offixing nitrogenfrom atmospheric, molecular nitrogen (N2) intoammonia(NH3).The chemical reaction is:
Ammonia is converted to another form,ammonium(NH+4), usable by (some) plants, by the following reaction:
This arrangement means that the root nodules are sources of nitrogen for legumes, making them relatively rich in nitrogenousamino acidsandprotein. Nitrogen is therefore a necessaryingredientin the production of proteins.
When a legume plant dies in the field, for example following theharvest, all of its remaining nitrogen, incorporated intoamino acidsinside the remaining plant parts, is released back into the soil. In the soil, the amino acids are converted to nitrate (NO−3), making the nitrogen available to other plants, thereby serving as fertilizer for future crops.
In many traditional andorganic farmingpractices,crop rotationorpolycultureinvolving legumes is common. By alternating between legumes and non-legumes, or by growing both together for part of the growing season, the field can receive a sufficient amount of nitrogenous compounds to produce a good result without adding nitrogenous fertilizer. Legumes are often used asgreen manure.
Sri Lanka developed thepolyculturepractice known as coconut-soybeanintercropping. Grain legumes are grown in coconut (Cocos nuficera) groves in two ways: intercropping or as a cash crop. These are grown mainly for their protein, vegetable oil and ability to uphold soil fertility.However, continuous cropping after 3–4 years decrease grain yields significantly.
A common pest of grain legumes that is noticed in the tropical and subtropical Asia, Africa, Australia and Oceania are minuscule flies that belong to the familyAgromyzidae, dubbed "bean flies". They are considered to be the most destructive. The host range of these flies is very wide amongst cultivated legumes. Infestation of plants starts from germination through to harvest, and they can destroy an entire crop in early stage.Black bean aphidsare a serious pest to broad beans and other beans. Common hosts for this pest are fathen, thistle and dock.Pea weevilandbean weevildamage leaf margins leaving characteristics semi-circular notches.Stem nematodesare very widespread but will be found more frequently in areas where host plants are grown.
Common legume diseases includeanthracnose, caused byColletotrichum trifolii;common leaf spotcaused byPseudomonas syringaepv. syringae; crown wart caused byPhysoderma alfalfae;downy mildewcaused byPeronospora trifoliorum; root rot caused byFusariumspp.; rust caused byUromyces striatus; crown and stem rot caused bySclerotinia trifoliorum;Southern blightcaused bySclerotium rolfsii; pythium (browning) root rot caused byPythiumspp.;fusarium wiltcaused byFusarium oxysporum; root knot caused byMeloidogyne hapla. These are all classified as biotic problems.
Abiotic problems include nutrient deficiencies, (nitrogen, phosphorus, potassium, copper, magnesium, manganese, boron, zinc), pollutants (air, water, soil, pesticide injury, fertilizer burn), toxic concentration of minerals, and unfavorable growth conditions.
Seed viability decreases with longer storage time. Studies ofvetch,broad beans, and peas show that they last about 5 years in storage. Environmental factors that are important in influencing germination are relative humidity and temperature. Two rules apply to moisture content between 5 and 14 percent: the life of the seed will last longer if the storage temperature is reduced by 5 degree Celsius. Secondly, the storage moisture content will decrease if temperature is reduced by 1 degree Celsius.
Cultivated legumes encompass a diverse range ofagriculturalclassifications, spanningforage,grain, flowering, pharmaceutical/industrial, fallow/green manure, and timber categories. A notable characteristic of many commercially cultivated legume species is their versatility, often assuming multiple roles concurrently. The extent of these roles is contingent upon the stage of maturity at which they are harvested.
Grain legumes are cultivated for their seeds,for humans and animals to eat, or for oils for industrial uses. Grain legumes includebeans,lentils,lupins,peas, andpeanuts.
Legumes are a key ingredient in vegan meat and dairysubstitutes. They are growing in use as a plant-based protein source in the world marketplace.Products containing legumes grew by 39% in Europe between 2013 and 2017.
There is acommon misconceptionthat adding salt before cooking prevents them from cooking through. Legumes may not soften because they are old, or because ofhard wateroracidicingredients in the pot; salting before cooking results in betterseasoning.
Legumes are a significant source ofprotein,dietary fibre,carbohydrates, anddietary minerals; for example, a 100 gram serving of cookedchickpeascontains 18 percent of theDaily Value(DV) for protein, 30 percent DV for dietary fiber, 43 percent DV forfolateand 52 percent DV formanganese.
Legumes are an excellent source ofresistant starch; this is broken down bybacteriain thelarge intestineto produceshort-chain fatty acids(such asbutyrate) used by intestinal cells forfood energy.
Forage legumes are of two broad types. Some, likealfalfa,clover, vetch (Vicia), stylo (Stylosanthes), orArachis, are sown inpastureand grazed by livestock. Others, such asLeucaenaorAlbizia, are woody shrubs or trees that are either broken down by livestock or regularly cut by humans to provide fodder. Legume-based feeds improve animal performance over a diet of perennial grasses. Factors include larger consumption, faster digestion, and higherfeed conversion rate.
The type of crop grown for animal rearing depends on the farming system. In cattle rearing, legume trees such asGliricidia sepiumcan be planted along edges of fields to provide shade for cattle, the leaves and bark are often eaten by cattle. Green manure can be grown between harvesting the main crop and the planting of the next crop.
Legume species grown for their flowers includelupins, which are farmed commercially for their blooms as well as being popular in gardens worldwide. Industrially farmed legumes includeIndigoferaandAcaciaspecies, which are cultivated fordyeandnatural gumproduction, respectively.Falloworgreen manurelegume species are cultivated to be tilled back into the soil in order to exploit the high levels of captured atmospheric nitrogen found in the roots of most legumes. Numerous legumes farmed for this purpose includeLeucaena,Cyamopsis, andSesbaniaspecies. Various legume species are farmed for timber production worldwide, including numerousAcaciaspecies andCastanospermum australe.
Some legume trees, like thehoney locust(Gleditsia) can be used inagroforestry.Others, including theblack locust(Robinia pseudoacacia),Kentucky coffeetree(Gymnocladus dioicus),Laburnum,and the woody climbing vineWisteria, havepoisonouselements.
Neanderthalsandearly modern humansused wild pulses when cooking meals 70,000 to 40,000 years ago.Traces of pulse production have been found around theRavi River(Punjab), the seat of theIndus Valley civilisation, fromc.3300 BC. Meanwhile, evidence of lentil cultivation has also been found in Egyptianpyramidsandcuneiformrecipes.Dry pea seeds have been discovered in a Swiss village that are believed to date back to theStone Age. Archaeological evidence suggests that these peas must have been grown in the eastern Mediterranean andMesopotamianregions at least 5,000 years ago and in Britain as early as the 11th century.The soybean was domesticated around 5,000 years ago in China from a descendant of the wild vineGlycine soja.
The oldest-known domesticated beans in the Americas were found inGuitarrero Cave, an archaeological site inPeru, and dated to around the second millennium BCE.Genetic analyses of the common beanPhaseolusshow that it originated inMesoamerica, and subsequently spread southward, along withmaizeand squash, traditional companion crops.In the United States, the domesticated soybean was introduced in 1770 byBenjamin Franklinafter he sent seeds to Philadelphia from France.
The International Year of Pulses 2016 was declared by theSixty-eighth session of the United Nations General Assembly.TheFood and Agriculture Organization of the United Nationswas nominated to facilitate the implementation of the year in collaboration with governments, relevant organizations, non-governmental organizations and other relevant stakeholders. Its aim was to heighten public awareness of the nutritional benefits of pulses as part ofsustainable foodproduction aimed towardsfood securityandnutrition. The year created an opportunity to encourage connections throughout the food chain that would better use pulse-based proteins, further global production of pulses, better usecrop rotationsand address challenges in the global trade of pulses.