Hevea brasiliensis

Hevea brasiliensis

The Pará rubber tree or sharinga tree, seringueira, rubber tree, rubber plant (Hevea brasiliensis (Willd. ex A. Juss.) Müll.Arg., 1865) is an arboreal species belonging to the Euphorbiaceae family.

Systematic –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Plantae,
Division Magnoliophyta,
Class Magnoliopsida,
Order Euphorbiales,
Family Euphorbiaceae,
Genus Hevea,
Species H. brasiliensis.
The term is basionym:
– Siphonia brasiliensis Willd. ex A.Juss..
The terms are synonymous:
– Hevea brasiliensis f. acreana (Ule) Ducke;
– Hevea brasiliensis f. angustifolia (Ule ex Huber) Ule;
– Hevea brasiliensis f. latifolia (Ule ex Huber) Ule;
– Hevea brasiliensis f. randiana (Huber) Ducke;
– Hevea brasiliensis subsp. granthamii Barth;
– Hevea brasiliensis var. acreana Ule;
– Hevea brasiliensis var. angustifolia Ule;
– Hevea brasiliensis var. angustifolia Ule ex Huber;
– Hevea brasiliensis var. janeirensis (Müll.Arg.) Pax;
– Hevea brasiliensis var. latifolia Ule;
– Hevea brasiliensis var. latifolia Ule ex Huber;
– Hevea brasiliensis var. randiana (Huber) Pax;
– Hevea brasiliensis var. stylosa Huber;
– Hevea granthamii Bartlett;
– Hevea janeirensis Müll.Arg.;
– Hevea randiana Huber;
– Hevea sieberi Warb.;
– Siphonia brasiliensis Willd.;
– Siphonia janeirensis (Müll.Arg.) O.F.Cook;
– Siphonia ridleyana O.F.Cook.

Etymology –
The term Hevea comes from “heve”, the term used to call the tree by the indigenous people of the Amazon.
The specific epithet brasiliensis means Brazil, which indicates one of its places of origin.

Geographic Distribution and Habitat –
Hevea brasiliensis is a native plant of the Amazon and present in a native range that includes: Bolivia, Brazil, Colombia, French Guiana, Peru and Venezuela.
Its natural habitat is that of the Amazon rainforest, on predominantly clayey soils, up to around 600 m above sea level. It is often found in periodically flooded areas, but larger trees are found on well-drained uplands. In its natural habitat it forms part of the intermediate floor of the tropical forest.

Description –
Hevea brasiliensis is a deciduous tree which, in nature, grows to a height of approximately 43 m and has a conical crown. Cultivated trees are generally much smaller because latex extraction limits their growth.
It has a cylindrical trunk and may have a swollen, bottle-shaped base.
The bark is a shade of brown and the inner bark exudes latex when damaged.
The leaves are compound, trifoliate, and are arranged in a spiral on a 15-25 cm long petiole; the leaflets are elliptical-lanceolate to obovate, long pointed, with an entire margin, 5-18 cm long and 2-8 cm wide, leathery, dark green above, paler below, with 2-3 glands at the base; the young leaves are bronze in color.
The inflorescences are pubescent panicles, borne in the axils of the leaves of the young branches; they are 15-20 cm long, with unisexual flowers that give off a penetrating odor, the female ones, 5-5.5 mm in diameter and 5-7 mm long, are located at the end of the central axis and the main lateral ramifications , the male ones, 4.5-5 mm in diameter and 4.5-6 mm long, much more numerous (with a ratio of approximately 70:1), on the rest of the inflorescence.
The flowers are petalless, greenish yellow in color with a calyx with five triangular lobes; the female flowers are made up of a tricarpellar ovary with three white sessile stigmas, the male ones have ten stamens in two whorls of five above a stem column.
Pollination is predominantly cross-pollinated; it is anemophilous and entomophilous.
The fruits are three-lobed capsules of 3-5 cm in diameter, explosively dehiscent; they contain 3 ellipsoidal seeds, 2-4 cm long, shiny, greyish in color with dark brown spots, which are thrown at distances of up to 20 m.

Cultivation –
Hevea brasiliensis is a fast-growing plant and is the most important rubber-producing tree in the world.
It is widely cultivated for its latex in lowland humid tropical areas, roughly between 15° N and 10° S, where there is relatively little variation in temperature.
Many improved forms have been developed.
The tree also has many other uses, including food, oil, lumber and fuel.
For cultivation it needs a humid tropical lowland climate and grows best at altitudes of 300 – 500 meters, but also succeeds at altitudes of up to 900 meters. However, planting above 400 – 500 meters is generally not recommended because trees at higher altitudes tend to be smaller, with less vigorous growth and with reduced production of both latex and timber.
It grows best in areas where the average annual temperature is between 23 and 35°C and an average annual rainfall is between 1,500 and 3,000 mm, although it can tolerate up to 4,000 mm.
In some areas, rubber can tolerate a dry period of 2-3 months.
From a pedological point of view, it prefers fertile soil, which retains humidity, in light shade, where the plants tolerate a certain amount of water stagnation. It tolerates a wide pH range between 4 and 8, although it performs better in acidic soils.
However, it does not tolerate calcareous areas and shallow, poorly drained or peaty soils should be avoided. It grows best in deep, well-drained clay soils, covered by natural undergrowth or legume cover crops and protected from erosion.
It also requires protection from strong winds.
The plants can be exploited for their latex from around the age of 7.
The root system has a well-developed taproot with widespread lateral roots.
In areas with high rainfall, good internal soil drainage is important. Strong winds can break trunks and branches; however, there are clones that are more wind resistant.
Only a few clones are self-incompatible, but most benefit from cross-pollination or hand pollination.
The economic life cycle of a rubber plantation is, at most, 30 – 35 years, after which replanting is necessary.
The plant reproduces by seed, which has a short-term germination rate, a few weeks if appropriately preserved, with germination times of 1-3 weeks and first flowering after 5-7 years, by micropropagation, but usually by grafting in order to maintain varietal characteristics. Rootstocks obtained from seeds that are one year old or more frequently 3-5 months old are used, which have a higher success rate, with a rootstock of the same age as the rootstock.

Customs and Traditions –
Hevea brasiliensis is a plant known by various common names, including: Pará rubber tree, rubber tree (English); kayu getah, kayu karet, pokok getah para (Indonesian); caoutchouc (French); rubber tree (Italian); seringa, seringueira (Portuguese – Brazil); caucho, caucho do Para, hule, jebe, syringa (Spanish); kautschukbaum, parakautschukbaum (German); katoh, yang phara (Thai).
This plant has enormous economic importance as it is the primary source for the production of rubber which is obtained through the processing of latex which is collected by making incisions on the bark.
The seeds contain cyanic compounds which are poisonous to humans if left untreated.
In the 19th century, its commercial exploitation, linked to the discovery of the vulcanization method in 1839, made the fortune of the Brazilian cities of Manaus and Belém.
Starting from the year 1873 there were several attempts to grow this plant outside Brazil. After several attempts, botanists at the Royal Botanic Gardens at Kew managed to germinate a dozen seeds. The shoots were transferred to India for cultivation but did not take root. A second attempt was made with over 70,000 seeds sent to Kew in 1875. About 4% of them germinated, and in 1876 about 2,000 seedlings were sent to Ceylon and Singapore, to the botanical gardens administered by the British botanist Henry Nicholas Ridley. This time the attempt was successful and the rubber tree soon spread to most of the British colonies in Asia.
Indeed, once established outside its native country, rubber was widely propagated in the British colonies. Rubber trees were brought to the botanical gardens of Buitenzorg, Java, in 1883. By 1898, a rubber plantation had been established in Malaya, and by the early 20th century imported Chinese workers constituted the dominant workforce in rubber production .
The cultivation of the tree in South America (Amazon) ended, however, at the beginning of the 20th century due, above all, to the ascomycete Pseudocercospora ulei, also called Microcyclus ulei, or Dothidella ulei, endemic to the Amazon basin.
This downy mildew was considered one of the five most aggressive diseases in commercial crops in South America. Rubber production then moved to parts of the world where it is not indigenous and therefore not affected by local plant diseases. Today, most rubber tree plantations are found in South and Southeast Asia, and in 2011 the top rubber-producing countries were Thailand, Indonesia, Malaysia, India, and Vietnam.
Once upon a time, however, this plant only grew in the Amazon forest. In Brazil, before the name was changed to ‘Seringueira’, the initial name of the plant was ‘Pará rubber tree’, derived from the name of the province of Grão-Pará. In Peru the tree was called ‘árbol del caucho’ and the latex extracted from it was called ‘caucho’. The tree was used to obtain rubber by the indigenous people who inhabited its geographical distribution. The Olmec people of Mesoamerica extracted and produced similar forms of primitive rubber from similar latex-producing trees such as Castilla elastica as early as 3,600 years ago. Rubber was used, among other things, to make the balls used in the Mesoamerican ball game.
Unfortunately, for the cultivation of this plant, the toxicity of arsenic to insects, bacteria and fungi has led to massive use of arsenic trioxide in rubber plantations, especially in Malaysia.
Most rubber trees in Southeast Asia are clones of varieties highly susceptible to Pseudocercospora ulei. For these reasons, environmental historian Charles C. Mann, in his 2011 book, 1493: Uncovering the New World Columbus Created, predicted that Southeast Asian rubber plantations will be devastated by blight in the not-too-distant future, thus creating a potential calamity for the international industry.
The rubber tree takes seven to ten years to produce its first crop. Harvesters make incisions in the latex pots, deep enough to touch the pots without damaging the tree’s growth, and the latex is collected in small buckets. This process is known as rubber tapping. Latex production is highly variable from tree to tree and between clone types.
Since latex production declines with age, rubber trees are generally cut down when they reach 25 to 30 years of age. The previous practice was to burn the trees, but in recent decades the wood has been harvested for making furniture.
From a biochemical point of view, Hevea brasiliensis produces cyanogenic glycosides (CG) as a defense, concentrated in the seeds. Although effective against other attackers, cyanogenic glycosides are not very effective against pathogenic fungi. In rare cases, they are even harmful. This is the case of the rubber tree, which actually suffers worse than Pseudocercospora ulei when it produces more cyanogenic glycosides. This may be due to the fact that cyanide inhibits the production of other defensive metabolites. This results in significantly divergent subpopulations with selection for or against cyanogenic glycosides, depending on local probabilities of fungal or nonfungal parasite pressure. The carbon and nitrogen in CGs are recycled for growth and latex production if necessary, making them an attractive nitrogen store, especially if the plant is deprived of light and storage in photosynthetic proteins would therefore be useless . α-hydroxynitriles are probably contained in the cytoplasm. Linamarin is hydrolyzed by a companion linamarase, a β-glycosidase. Linamarase from Hevea brasiliensis acts on linamarin because it is a monoglucoside, while it does not act on linustatin because it is a diglucoside: in fact, the production of lovastatin inhibits the cleavage of linamarin by linamarase. This allows post-synthesis intra-plant transport of linustatin without risking premature cleavage.
Other uses include agroforestry uses.
It is possible to combine this plant with coffee or cocoa, perhaps in combination with ipecac. After a few years under legumes, no nitrogen fertilizer may be needed, but phosphorus, magnesium and potassium may be limiting in some areas.
The pressed cake or extracted flour can be used as fertilizer.
The seeds contain a semi-drying pale yellow oil, known as Para gum seed oil.
Boiling the seed removes the poison and releases the oil, which can be used for lighting, soap making, paints and varnishes.
The oil can be used as an effective treatment against houseflies and lice.
The heartwood is light cream in color, often with a pink tinge when fresh, darkening with exposure to light straw or light brown, not sharply demarcated from the sapwood. The grain is straight to slightly interlocking, the texture is moderately coarse but uniform. Sawn wood often shows black streaks with inclusion of bark material, the result of inadequate tapping practices with damaged or removed cambia; in freshly sawn wood there is a characteristic and distinct latex smell. Most of the lumber is used to make furniture. Other uses include interior trim, mouldings, e.g. For wood paneling, picture frames, drawer runners, cabinet and other handles, parquet floors, numerous household utensils, blockboard cores, pallets, cages, coffins, veneers and laminated wood, for stairs and door and window elements.
Because wood is only moderately durable when exposed to the elements, it should not be used for outdoor purposes.
Offcuts and other wood residues have been successfully used in Malaysia for the production of particle board, wood-cement board and medium density fibreboard.
The wood was previously considered a by-product of rubber plantations and used for charcoal production or as firewood, brick making, tobacco drying and rubber drying.
Wood waste is an excellent medium for growing mushrooms, especially oyster mushrooms (Pleurotus spp.).

Preparation Method –
Hevea brasiliensis is a plant that is cultivated, or used in nature, for multiple uses, both for food purposes and, above all, for the extraction of the latex from which rubber is obtained.
In food use, the cooked seeds are eaten which, although poisonous, constitute the basic food of the local jungle populations. However, the seeds must be treated by soaking them for a prolonged period or boiling them to destroy the cyanic poisons.
The seeds contain 40-50% oil. This is suitable for use as food.
However, there are no known medicinal uses.
As mentioned, by drilling the trunk a latex is obtained.
Latex coagulates with the aid of acetic acid, formic acid and alum and is the main source of natural rubber, used in a wide variety of applications including car tyres, shoes and boots, balls, rubber bands, erasers, etc.
It is also widely used by local people to make household items such as water bottles, balls, etc.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (ed.), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora d’Italia, Edagricole, Bologna.
– Treben M., 2000. Health from the Lord’s Pharmacy, Advice and experiences with medicinal herbs, Ennsthaler Editore.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/322758495/original.jpeg
– https://herbaria.plants.ox.ac.uk/bol/Content/Projects/plants400/images/hires/HEVEA_31470.JPG

Attention: Pharmaceutical applications and food uses are indicated for informational purposes only, they do not represent in any way a medical prescription; we therefore decline any responsibility for their use for healing, aesthetic or food purposes.