Tuesday, 17 September 2019
Hevea brasiliensis:The Rubber Tree :: Botany
Hevea brasiliensis:The Rubber Tree During the Age of Exploration many people were sent out to seek unknown plant species that might serve as raw material, remedy, or ornament. Of all the great feats of that era of botanical discovery, none was more imposing than that of the domestication of rubber. New World inhabitants had shown rubber, which they obtained from several tropical plant species, to early explorers, including Columbus. Since it was an unstable product, it remained for more than three centuries a mere curiosity. Then, in 1839, it was found that through treatment with sulfur and heat (vulcanization), rubber's elastic properties could be made more permanent. (1) Hevea brasiliensis is the source of virtually all the world's rubber production. Cutting the bark of this tree releases the latex which is then collected, preserved, and stabilized. The latex is located in the inner bark of the tree and flows in the vessels of the tree. Latex is thought to be a defense against insect predators for the tree. (1) Hevea brasiliensis was first found in the Amazon basin. The rubber trade became a mainstay of the Brazilian economy, providing at its height almost 40 % of its export revenues. It was not long before the idea was conceived of domesticating rubber. However, Brazil was not the site of the successful commercialization of rubber. Rubber cultivation was, instead, transferred to Southeast Asia. Soon abundant and cheap, rubber was put to thousands of uses. Its reduced cost was an important factor in the emergence of a mass market of automobiles; from two-thirds to three-quarters of the demand for rubber soon came from the makers of tires and tubes for motor vehicles. (1) After tires, latex products, footwear, belts and hoses, and wire cables are the most important uses for rubber. (3) Rubber is harvested in Africa, Central and South America, and in Asia, the latter accounting for greater than 90% of production. There are 11 species of Hevea. Hevea brasiliensis is a member of the Euphorbiaceae family (spurge family). Although not limited to the Euphorbiaceae, latex production is one of its distinguishing characteristics. (7) The plants of the Euphorbiaceae family are mostly monoecious herbs, shrubs, and trees, sometimes succulent and cactus-like, and comprise one of the largest families of plants with about 300 genera and 7,500 species that are further characterized by the frequent occurrence of milky sap. (6) The flowering and pollination of the Hevea brasiliensis tree are also distinguishing characteristics of this plant.