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Plants produce resins for various reasons whose relative importances are debated. It is known that resins seal the plant's wounds, kill insects and fungi, and also allow the plant to eliminate excess metabolites.

Resin as produced by most plants is a viscous liquid, typically composed mainly of volatile fluid terpenes, with lesser components of dissolved non-volatile solids which make resin viscous and sticky. The commonest terpenes in resin are the bicyclic terpenes alpha-pinene , beta-pinene , delta-3 carene and sabinene , the monocyclic terpenes limonene and terpinolene , and smaller amounts of the tricyclic sesquiterpenes longifolene , caryophyllene and delta-cadinene . The individual components of resin can be separated by fractional distillation.

A few plants produce resins with different compositions, most notably Jeffrey Pine and Gray Pine, the volatile components of which are largely pure n-heptane with little or no terpenes. The exceptional purity of the n-heptane distilled from Jeffrey Pine resin, unmixed with other isomers of heptane, led to its being used as the defining zero point on the octane rating scale of petrol quality. As heptane is explosively flammable, distillation of resins containing it is very dangerous; before Jeffrey Pine was distinguished as a separate species from the similar, but terpene-producing Ponderosa PinePonderosa Pine Ponderosa Pine branch , , Scientific classification : Plantae : Pinophyta : Pinopsida : Pinales : Pinaceae Pinus ponderosa Binomial name Pinus ponderosa Ponderosa Pine Pinus ponderosa is a widespread and very variable pine native to western in the mid to late 19th century, some resin distilleries in CaliforniaCalifornia is a state located in the western United States, bordering the Pacific Ocean. The most populous and third largest state in the U. California is both physically and demographically diverse. The state's official nickname is "The Golden State", wh exploded as a result.

Solidified resin from which the volatile terpene components have been removed by distillation is known as rosinRosin is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vapourise the volatile liquid terpene components. It is semi-transparent and varies in color from yellow to black. At room. Typical rosin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, non-odourous or having only a slight turpentine odour and taste. It is insoluble in water, mostly soluble in alcohol, essential oils, ether and hot fatty oils, softens and melts under the influence of heat, is not capable of sublimation, and burns with a bright but smoky flame. This comprises a complex mixture of different substances including organic acids named the resin acid s. These are closely related to the terpenes, and derive from them through partial oxidation. Resin acids can be dissolved in alkaliThe word alkali can mean In chemistry, an alkali is the solution of a base in water. Since a base is defined as a substance which yields or creates hydroxide ions when dissolved in water, an alkali is a solution of hydroxide anions and their correspondings to form resin soap s, from which the purified resin acids are regenerated by treatment with acids. Examples of resin acids are abietic acidAlso known as: abietinic acid, sylvic acid, 13-isopropylpodocarpa-7,13-dien-15-oic acid Molecular formula: C HCOOH CAS No: 514-10-3 EINECS No: 208-173-3 The ester is called an abietate. Appearance: yellow resinous powder, crystals or chunks Melting point: (sylvic acid), C₂₀H₃₀O₂, and pimaric acid , C₂₀H₃₅O₂, a constituent of gallipot resin . Abietic acid can also be extracted from rosin by means of hot alcohol; it crystallizes in leaflets, and on oxidation yields trimellitic acid , isophthalic acid and terebic acid . Pimaric acid closely resembles abietic acid into which it passes when distilled in a vacuum; it has been supposed to consist of three isomers.

Some resins when soft are known as oleo-resins , and when containing benzoic acid or cinnamic acid they are called balsams. Other resinous products are in their natural condition mixed with gum or mucilaginous substance s and known as gum resin s. Many compound resins have distinct and characteristic odours, from their admixture with essential oils.

The hard transparent resins, such as the copals, dammar s, mastic and sandarach , are principally used for varnishes and cement, while the softer odoriferous oleo-resins ( frankincense, turpentine, copaiba ) and gum resins containing essential oils ( ammoniacum , asafoetida, gamboge , myrrh, and scammony ) are more largely used for therapeutic purposes and incense.

Certain resins are obtained in a fossilized condition, amber being the most notable instance of this class; African copal and the kauri gum of New Zealand are also procured in a semi-fossil condition.