Pará rubber tree

Pará rubber tree

Pará rubber tree, large tree (Hevea brasiliensis) of the family Euphorbiaceae (spurge family), native to tropical South America and the source of the greatest amount and finest quality of natural rubber. Today most Pará rubber is produced from trees grown on plantations in Asia and to a lesser extent in Africa. The yellow or white latex from which rubber is made occurs in numerous specialized latex vessels in the bark, especially outside the phloem. The tree is tapped by making careful incisions, as deep as possible without injuring the tree's growth, in a herringbone pattern or often in a lefthand spiral of 30° around the trunk, for the latex vessels spiral to the right at an angle of about 30° from the horizontal. The latex is collected in small cups and then treated—usually by coagulating it with acid, pressing it free of water, and drying the resultant sheets in a smokehouse to ready them for shipment. The size of the tree, the quality of the latex, and the number of taps possible varies with individual trees; the quantity of latex increases with the age of the tree, which may grow to a height of over 100 ft (30 m). Cultivated trees are tapped throughout the year, usually in the early morning, when the latex flow is greatest. Sometimes other trees that yield latex are also called Pará rubber trees. Pará rubber trees are classified in the division Magnoliophyta, class Magnoliopsida, order Euphorbiales, family Euphorbiaceae.

The Pará rubber tree (Hevea brasiliensis), often simply called rubber tree, is a tree belonging to the family Euphorbiaceae and the most economically important member of the genus Hevea. It is of major economic importance because its sap-like extract (known as latex) can be collected and is the primary source of natural rubber.

Description

The tree can reach a height of over 30m (98.4 feet). The white or yellow latex occurs in latex vessels in the bark, mostly outside the phloem. These vessels spiral up the tree in a right-handed spiral which forms an angle of about 30 degrees with the horizontal.

Harvest

Once the trees are 5-6 years old, the harvest can begin: incisions are made orthogonal to the latex vessels, just deep enough to tap the vessels without harming the tree's growth, and the sap is collected in small buckets. This process is known as rubber tapping. Older trees yield more latex, but they stop producing after 26-30 years.

History

The Pará rubber tree initially grew only in the Amazon Rainforest. Increasing demand and the discovery of the vulcanization procedure in 1839 led to a boom in that region, enriching the cities of Belém and Manaus. The name of the tree derives from Pará, the second largest Brazilian state, that contains Belém as capital, mainly city and tech-financial centre.

There had been an attempt made, in 1873, to grow rubber outside Brazil. After some effort, twelve seedlings were germinated at the Royal Botanic Gardens, Kew. These were sent to India for cultivation, but died. A second attempt was then made, some 70,000 seeds being sent to Kew in 1875. About 4% of these germinated, and in 1876 about 2000 seedlings were sent, in Wardian cases, to Ceylon, and 22 sent to the Botanic Gardens in Singapore. Once established outside its native country, rubber was extensively propagated in the British colonies. Rubber trees were brought to the botanical gardens at Buitenzorg, Java in 1883. By 1898, a rubber plantation had been established in Malaya, and today most rubber tree plantations are in Southeast Asia and some also in tropical Africa. Efforts to cultivate the tree in its native South America were unsatisfactory.

Uses

The wood from this tree, referred to as parawood or rubberwood, is used in the manufacture of high-end furniture. It is valued for its dense grain, minimal shrinkage, attractive colour and acceptance of different finishes. It is also prized as an "environmentally friendly" wood, as it makes use of trees that have been cut down at the end of their latex-producing cycle.

Synonyms

The genus Hevea is also known as:

See also

Gallery

References

Further references

Zhang, J., Huss, V.A.R., Sun, X., Chang, K. and Pan, D. 2008. Morphology and phylogenetic position of a trebouxiophycean green algae (Chlorophyta) growing on th rubber tree, Hevea brasiliensis, with the description of a new genus and species. Eur. J. Phycol. 43(2): 185 - 193.

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