Santalum album is a small tropical tree, and the traditional source of sandalwood oil. It is native to Indonesia (Java and the Lesser Sunda Islands), the Philippines, and Western Australia. It is commonly known as the white sandalwood or Indian sandalwood. It was one of the plants exploited by Austronesian arboriculture and it was introduced by Austronesian sailors to Mainland Southeast Asia, South Asia and East Asia, during the ancient spice trade, becoming naturalized in South India by at least 1300 BCE. It was greatly valued for its fragrance, and is considered sacred in some religions like Hinduism. The high value of the species has caused over-exploitation, to the point where the wild population is vulnerable to extinction. Indian sandalwood still commands high prices for its essential oil owing to its high alpha-santalol content, but the lack of sizable trees has essentially eliminated its former use for fine woodworking. The plant is long-lived, but harvest is only viable after many years.
Description
Santalum album is an evergreen tree that grows between 4–9 metres (13–30 feet). The tree is variable in habit, usually upright to sprawling, and may intertwine with other species. The plant parasitises the roots of other tree species, with a haustorium adaptation on its own roots, but without major detriment to its hosts. An individual will form a non-obligate relationship with a number of other plants. Up to 300 species (including its own) can host the tree's development—supplying macronutrients phosphorus, nitrogen and potassium, and shade—especially during early phases of development. It may propagate itself through wood suckering during its early development, establishing small stands. The reddish or brown bark can be almost black and is smooth in young trees, becoming cracked with a red reveal. The heartwood is pale green to white as the common name indicates. The leaves are thin, opposite and ovate to lanceolate in shape. Glabrous surface is shiny and bright green, with a glaucous pale reverse. Fruit is produced after three years, viable seeds after five. These seeds are distributed by birds.
Taxonomy
Nomenclature
The nomenclature for other "sandalwoods" and the taxonomy of the genus are derived from this species' historical and widespread use. Etymologically it is derived from Sanskrit chandanam, meaning "wood for burning incense", and related to candrah, meaning "shining, glowing". Santalum album is included in the family Santalaceae, and is commonly known as white or East Indian sandalwood. The name, Santalum ovatum, used by Robert Brown in Prodromus Florae Novae Hollandiae (1810) was described as a synonym of this species by Alex George in 1984. The epithet album refers to the "white" of the heartwood. The species was the first to be known as sandalwood. Other species in the genus Santalum, such as the Australian S. spicatum, are also referred to as true sandalwoods, to distinguish them from trees with similar-smelling wood or oil.
Phytochemistry Sandalwood oil consists of about 80% α-santalol and β-santolol, predominantly the former, which are sesquiterpenes. Attempts to synthesise these date to 1947 by Givaudan in Switzerland. The resulting isobornyl cyclohexanol can be distinguished from santalol, but is much cheaper. Since then other synthetic sandalwood oils have been used in laundry detergents and textiles. Three of the terpene synthase genes producing components employed in host defense are present in S. album.
Distribution and history Sandalwood is originally native to dry areas in India, Indonesia (Java and the Lesser Sunda Islands), the Philippines, and Western Australia, where it is found with close congeners. It was introduced very early (c. 1500 BCE) into Dravidian regions of South Asia via the Austronesian maritime spice trade, along with other Austronesian domesticates like areca nut and coconuts. It first appears in archaeological records in South Asia in the southern Deccan by 1300 BCE. It became naturalized in these regions where dry sandy soils are common. Sandalwood is now cultivated in India, Sri Lanka, Indonesia, Malaysia, the Philippines and Northern Australia.
Habitat and growth
S. album occurs from coastal dry forests up to 700 metres (2,300 ft) elevation. It normally grows in sandy or well drained stony red soils, but a wide range of soil types are inhabited. This habitat has a temperature range from 0 to 38 °C (32 to 100 °F) and annual rainfall between 500 millimetres (20 in) and 3,000 millimetres (120 in). S. album can grow up to 9.1 metres (30 ft) vertically. It should be planted in good sunlight and does not require a lot of water. The tree starts to flower after seven years. When the tree is still young the flowers are white and with age they turn red or orange. The trunk of the tree starts to develop its fragrance after about 10 years of growth, but is not ready to harvest till after 20. The tree rarely lives more than 100 years.
Conservation S. album is recognized as a "vulnerable" species by the International Union for the Conservation of Nature (IUCN). It is threatened by over-exploitation and degradation to habitat through altered land use, fire (to which this species is extremely sensitive), Spike disease, agriculture, and land-clearing are the factors of most concern. To preserve this vulnerable resource from over-exploitation, legislation protects the species, and cultivation is researched and developed. In India, regulation of sandalwood cultivation, harvesting, transport and sale varies between states. Karnataka permitted private cultivation through a 2001 amendment, while regulatory changes in 2008 and 2022 expanded the entities permitted to purchase privately grown sandalwood. Requirements relating to harvesting, transit and marketing continue to apply and differ between states. The Indian government has placed a ban on the export of the timber.
Uses and production
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