Guar
| Guar Cyamopsis tetragonoloba |
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|---|---|
 |
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| Guar bean cluster | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Genus: | Cyamopsis |
| Species: | C. tetragonoloba |
| Binomial name | |
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Cyamopsis tetragonoloba (L.) Taub. |
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| Synonyms | |
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Cyamopsis psoralioides L. |
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Cyamopsis psoralioides L.
The Guar or cluster bean, with the botanical name Cyamopsis tetragonoloba, is an annual legume and the source of guar gum. It is also known as Gavar, Guwar, or Guvar bean.
The origin of Cyamopsis tetragonoloba is unknown, since it has never been found in the wild. It is assumed to have developed from the African species Cyamopsis senegalensis. It was further domesticated in India and Pakistan, where it has been cultivated for many centuries. Guar grows well in semiarid areas, but frequent rainfall is necessary.
This legume is a very valuable plant within a crop rotation cycle, as it lives in symbiosis with nitrogen-fixing bacteria. In fact, agriculturists in semi-arid regions of Rajasthan follow crop-rotation and use guar as a source to replenish the soil with essential fertilizers and nitrogen fixation, before the next crop. Guar as a plant has a multitude of different functions for human and animal nutrition but its gelling-agent-containing seeds (guar gum) are today the most important use. Demand is rising rapidly due to industrial use of guar gum in hydraulic fracturing (oil shale gas). About 80% of world production occurs in India and Pakistan, but due to strong demand, the plant is being introduced into new areas.
Cyamopsis tetragonoloba grows upright, reaching a maximum height of up to 2–3 m. It has a main single stem with either basal branching or fine branching along the stem. Thanks to taproots, the guar plant can access soil moisture in low soil depths. Additionally, this legume develops root nodules with nitrogen-fixing soil bacteria rhizobia in the surface part of its rooting system. Its leaves and stems are mostly hairy, dependent on the cultivar. Its fine leaves have an elongated oval shape (5 to 10 cm length) and of alternate position. Clusters of flowers grow in the plant axil and are of white to blueish color. The developing pods are rather flat and slim containing 5 to 12 small oval seeds of 5 mm length (TGW = 25-40 g). Usually, mature seeds are white or gray, but in case of excess moisture they can turn black and lose germination capacity. The chromosome number of guar seeds is 2n=14. The seeds of guar beans have a very remarkable characteristic. Its kernel consists of a protein-rich germ (43-46%) and a relatively large endosperm (34-40%), containing big amounts of the galactomannan. The latter is polysaccharide containing polymers of mannose and galactose in a ratio of 2:1 with many branches. Thanks to the latter, it exhibits a great hydrogen bonding activity having a viscosifying effect in liquids.
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Wikipedia