Hevea

Key takeaways

Hevea belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hevea to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hevea from memory before moving on to harder problems.

Reference excerpt

Hevea is a genus of flowering plants in the spurge family, Euphorbiaceae, with about ten members. It is also one of many names used commercially for the wood of the most economically important rubber tree, H. brasiliensis. The genus is native to tropical South America but is widely cultivated in other tropical countries and naturalized in several of them. It was first described in 1775.

Characteristics French botanist and explorer Jean Baptiste Christophore Fusée Aublet first described Hevea as a genus in 1775. H. brasiliensis and H. guianensis are large trees, often reaching more than 30 m (100 ft) in height. Most of the other members of the genus are small to medium trees, and H. camporum is a shrub of around 2 m (7 ft). Trees in this genus are either deciduous or evergreen. Certain species, namely H. benthamiana, H. brasiliensis and H. microphylla, bear "winter shoots", stubby side shoots with short internodes, scale leaves on the stem and larger leaves near the tip; on these, the leaves are shed leaving the tree bare before new shoots develop. The remaining species bear more vigorous side shoots which develop before the old foliage is shed and thus the tree remains green. The leaves consist of three, usually elliptical, leaflets which are held horizontally or slightly drooping in most species. The inflorescences have separate male and female flowers, with the females being at the end of the panicles. The fruits are capsules, usually with three seeds, which in all except two species (H. spruceana and H. microphylla) split explosively when ripe to eject the large seeds.

Distribution The genus occurs naturally in tropical South America, mostly in the Amazon basin. To the north of the basin, the land rises to the watershed of the Guiana Shield on the border between Brazil and Venezuela, and the southern foothills of these mountains form the northerly limit of the genus. It is also present in the upper reaches of the Orinoco River. The genus extends westwards as far as the foothills of the Andes and southwards to the foothills of the Mato Grosso. Its easterly limit is the Atlantic Ocean. The most widespread species is H. guianensis which occurs over the whole range of the genus. The Pará rubber tree (H. brasiliensis) occurs mainly south of the Amazon, as does H. camporum, but the greatest diversity occurs to the north of the river, in the Rio Negro region, where all the other species occur. In this area where there are variations in soil and topography and the rainforest experiences conditions of all-year-round humidity, the genus Hevea has been undergoing a high degree of speciation. The high humidity encourages the growth of fungal leaf diseases, and the species that are deciduous avoid immediate transfer of fungal spores from old leaves onto new growth. The Pará rubber tree has been introduced to and is naturalised in many tropical countries in Asia.

Habitat Each species has its own habitat requirements; H. brasiliensis grows on well-drained soils but tolerates light flooding; H. guianensis, H. pauciflora and H. rigidifolia grow in well-drained soil, on high river banks and on slopes; and H. camporum grows on savannahs. Other species such as H. benthamiana, H. microphylla and H. spruceana need wetter conditions in locations subject to seasonal flooding for several months each year, and H. nitida grows both in periodically inundated swamps and in drier locations such as rocky hillsides well above the flood level.

Rubber History

Rubber from Hevea trees comes from the sap that the trees produce to prevent the boring of insects.

Historical Uses Indigenous groups in Mesoamerica collected the sap through tapping. They formed rubber bouncing balls for games and also used dried sap to waterproof their clothing.

European Discovery The initial discovery is believed to be by Christopher Columbus in the 15th-16th century, through accounts of him returning with a rubber ball. The curiosity came from the soft, sticky texture when warm and hard, brittle texture when cold. There was no commercial development until the 19th century, beyond small-scale waterproofing and erasers.

Pneumatic tires In 1839, Charles Goodyear accidentally spilled a combination of rubber and sulfur on a hot stove. Through vulcanization the rubber maintained its elasticity when cold and was no longer sticky while hot. From this discovery, in 1887 pneumatic tires were created for both bicycles and cars, leading to an increase in rubber demand.

Botanical Piracy With the development of the pneumatic tire industry, trees were being tapped at too fast a rate to maintain. In response, Brazil banned the trading of Hevea trees and seeds to protect its primary export. However, in 1876 Henry Wickham, a British envoy from Kew Gardens, stole over 70,000 seeds which were shipped across the world. Only 12 seeds germinated and survived in Asia, where China and India were able to develop hevea plantations and dominate the rubber industry.

Species The following species are recognised:

Hevea benthamiana Müll.Arg. – Venezuela, SE Colombia, N Brazil Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg. – Pará rubber tree – Brazil, French Guiana, Venezuela, Colombia, Peru, Bolivia; naturalized in parts of Asia and Africa and on some tropical islands Hevea camargoana Pires – Marajó, Pará State in Brazil Hevea camporum Ducke – Amazonas State in Brazil Hevea guianensis Aubl. – Venezuela, Ecuador, Peru, Guyana, Suriname, French Guiana, Colombia, N Brazil Hevea microphylla Ule – Venezuela, Colombia, N Brazil Hevea nitida Mart. ex Müll.Arg. – Colombia, Amazonas State in Brazil Hevea pauciflora (Spruce ex Benth.) Müll.Arg. – Venezuela, Peru, Guyana, Suriname, French Guiana, Colombia, N Brazil Hevea rigidifolia (Spruce ex Benth.) Müll.Arg. – Vaupés region of Colombia, Amazonas State in Brazil Hevea spruceana (Benth.) Müll.Arg. – Guyana, Amazonas State in Brazil

References

External links Media related to Hevea at Wikimedia Commons Data related to Hevea at Wikispecies

Illustrations

Worked examples

Example 1 — a first encounter with Hevea

Start with the simplest possible case. Write down what Hevea claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hevea before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hevea ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hevea

In research: Hevea appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hevea in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hevea is common in secondary-school and first-year university syllabi. It links to neighbouring topics Crotonoideae, Euphorbiaceae genera, Rubber, so understanding it makes those chapters shorter.
In everyday life: Look for Hevea outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Hevea in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hevea means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hevea out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hevea in simple terms?

Hevea is a genus of flowering plants in the spurge family, Euphorbiaceae, with about ten members. It is also one of many names used commercially for the wood of the most economically important rubber tree, H. brasiliensis.

Why does Hevea matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hevea?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hevea.