| Pongamia | |
|---|---|
_near_Hyderabad_W_IMG_7633.jpg) | |
| Flowers | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Subfamily: | Faboideae |
| Tribe: | Millettieae |
| Genus: | Pongamia Adans. (1763), nom. cons. |
| Species: | P. pinnata |
| Binomial name | |
| Pongamia pinnata | |
| Varieties[1] | |
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| Synonyms[1] | |
Pongamia pinnata is a species of tree in the pea family,Fabaceae, native to eastern and tropical Asia, Australia, and the Pacific islands.[1][3][4][5] It is the sole species in genusPongamia.[6] It is often known by the synonymMillettia pinnata. Its common names includeIndian beech,Karanja, andPongame oiltree.[4][5]
Pongamia pinnata is alegume tree that grows to about 15–25 m (50–80 ft) in height with a largecanopy which spreads equally wide and creates dense shade. It may bedeciduous for short periods. It has a straight or crooked trunk, 50–80 cm (20–30 in) in diameter, with grey-brown bark, which is smooth or vertically fissured. Its wood is white colored.[7] Branches are glabrous with palestipulate scars. Theimparipinnate leaves of the tree alternate and are short-stalked, rounded, orcuneate at the base; ovate or oblong along the length; obtuse-acuminate at the apex; and not toothed on the edges. They are a soft, shiny burgundy when young and mature to a glossy, deep green as the season progresses, with prominent veins underneath.[8]
Flowering generally starts after 3–4 years with small clusters of white, purple, and pinkflowers blossoming throughout the year.[9] Theraceme-likeinflorescences bear two to four flowers that are stronglyfragrant and grow to be 15–18 mm (0.59–0.71 in) long. Thecalyx of the flowers is bell-shaped and truncated, while thecorolla is a rounded ovate shape with basal auricles and often with a central blotch of green color.[5][10]
Croppings ofindehiscent pods can occur by 4–6 years. The brown seed pods appear immediately after flowering, and mature in 10 to 11 months. The pods are thick-walled, smooth, somewhat flattened, and elliptical, but slightly curved with a short, curved point. The pods contain within them one or two bean-like brownish-red seeds, but because they do not split open naturally, the pods need to decompose before the seeds can germinate. The seeds are about 1.5–2.5 cm (0.59–0.98 in) long with a brittle, oily coat, and are unpalatable in natural form to herbivores.[8][10][7]
Pongamia pinnata is anoutbreedingdiploid legume tree, with a diploidchromosome number of 22.[10] Root nodules are of the determinate type (as those on soybean and common bean) formed by the causative bacteriumBradyrhizobium.
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The species is naturally distributed in tropical and temperate Asia, from India to Japan to Thailand toMalesia to north and northeastern Australia to some Pacific islands;[3][5] It has been propagated and distributed further around the world in humid andsubtropical environments from sea level to 1,360 m (Chingola, Zambia), although in theHimalayan foothills, it is not found above 600 m.[11] Withstanding temperatures slightly below 0 °C (32 °F) and up to about 50 °C (122 °F) and annual rainfall of 500–2,500 mm (20–98 in), the tree grows wild on sandy and rocky soils, includingoolitic limestone, and will grow in most soil types, even with its roots in salt water.[12]
The tree is well suited to intense heat and sunlight, and its dense network of lateral roots and its thick, longtaproot make it drought tolerant. The dense shade it provides slows the evaporation of surface water and itsroot nodules promotenitrogen fixation, a symbiotic process by which gaseousnitrogen (N2) from the air is converted intoammonium (NH4+, a form of nitrogen available to the plant).M. pinnatais also afreshwater flooded forest species, as it can survive total submergence in water for few months continuously.M. pinnata trees are common inTonlesap lake swamp forests inCambodia.[citation needed]
P. pinnata is now broadly distributed across India, Asia, Africa, northern Australia, and the Pacific and Caribbean Islands and it has been cultivated and transported since the nineteenth century or earlier. As a result, some literature declaresM. pinnata naturalized in Africa and certain parts of the United States, while its status as naturalized or native is uncertain in other regions.[13]
The species was first described asCytisus pinnatus byCarl Linnaeus in 1753. In 1898,Jean Baptiste Louis Pierre reclassified it asPongamia pinnata.[1] In 1984, Robert Geesink concluded that species ofPongamia andMillettia were easily confused, and consolidated thePongamia species intoMillettia. Subsequent studies revealed thatMillettia pinnata wasparaphyletic withinMillettia, and the species was reclassified asPongamia pinnata, the sole species in the revived genusPongamia.[14]
Pongamia pinnata is well-adapted toarid zones, and has many traditional uses. It is often used for landscaping as awindbreak or for shade due to the large canopy and showy, fragrant flowers. The flowers are used by gardeners ascompost for plants. The bark may be used to make twine or rope, and it also yields a black gum that has historically been used to treat wounds caused by poisonous fish. The wood is said to be beautifully grained, but splits easily when sawn, thus relegating it tofirewood, posts, and tool handles.[11] The tree's deep taproot and drought tolerance makes this tree ideal for controllingsoil erosion and bindingsand dunes.[11]
Pongamia pinnata seeds generally contain oil (27-39%), protein (17-37%), starch (6-7%), crude fiber (5-7%), moisture (15-20%), and ash content (2-3%). Nearly half of the oil content ofP. pinnata seeds isoleic acid.[15] Oil made from the seeds, known aspongamia oil, has been used aslamp oil, insoapmaking, and as alubricant. The oil has a high content oftriglycerides. Its disagreeable taste and odor are due to bitterflavonoid constituents, includingkaranjin, pongamol,tannin, andkaranjachromene.[12] These compounds induce nausea and vomiting if ingested in its natural form. The fruits, sprouts and seeds are used intraditional medicine.[12]
It can be grown inrainwater harvesting ponds up to 6 m (20 ft) in water depth without losing its greenery and remaining useful for biodiesel production.[16][17] Studies have shown seedlings with tolerance to salinity levels between 12 and 19 dS/m,[18] with an ability to tolerate salinity stresses of 32.5 dS/m.[19]
The seed oil has been found to be useful in diesel generators, and along withJatropha andcastor, it is being explored in hundreds of projects throughout India and the third world as feedstock forbiodiesel.[20]P. pinnata as a biofuel is commercially valuable to the rural populations of places such as India and Bangladesh, where the plant grows abundantly, because it can support the socioeconomic development of these areas.[21][22]
Several unelectrified villages have usedpongamia oil, simple processing techniques, and diesel generators to create their own grid systems to run water pumps and electric lighting.[23]
Research indicates potential use ofP. pinnata as a food source for cattle, sheep, and poultry, as its byproduct contains up to 30% protein.[24][25] As adaptive uses are increasing, the tree is being planted in former citrus growing regions that have declined in Florida and California because of disease and climate change conditions.[26]
| Biofuels | |
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| Energy from foodstock | |
| Non-food energy crops | |
| Technology | |
| Concepts | |
