Resin
Most plant resins are composed of terpenes. Specific components include alpha-pinene and beta-pinene. These molecules form the backbone of the substance. Smaller amounts contain tricyclic sesquiterpenes like longifolene. Some resins also hold a high proportion of resin acids. Rosins differ by containing diterpenes among other compounds. This chemical makeup makes them insoluble in water. They remain mixtures of organic compounds that do not dissolve easily.
Resins protect plants from insects and pathogens. They are secreted in response to injury. The liquid flows out when a tree trunk is cut or damaged. Resins repel herbivores and stop bacteria from entering wounds. Volatile phenolic compounds may attract predators of attacking insects. This biological function turns a sticky mess into a shield. Cedar of Lebanon cones show flecks of resin used historically. The process begins immediately after physical harm occurs to the organism.
Human use of plant resins has a long history documented in ancient Greece. Theophrastus wrote about these substances over two thousand years ago. Pliny the Elder recorded their uses in ancient Rome too. Frankincense and myrrh were highly prized in ancient Egypt. These materials required as incense in some religious rites. The oldest known use comes from the late Middle Stone Age in Southern Africa. People there used it as an adhesive for hafting stone tools. Amber trapped insects inside its hardened form during prehistoric times.
Examples of plant resins include amber and Balm of Gilead. Copal comes from trees of Protium copal and Hymenaea courbaril. Dammar gum originates from trees of the family Dipterocarpaceae. Dragon's blood flows from dragon trees of Dracaena species. Mastic comes from the mastic tree Pistacia lentiscus. Myrrh is harvested from shrubs of Commiphora. Sandarac resin grows on Tetraclinis articulata, the national tree of Malta. Kauri gum comes from trees of Agathis australis in New Zealand. African copal and kauri gum are procured in a semi-fossil condition.
Many materials are produced via conversion of synthetic resins to solids. Bisphenol A diglycidyl ether becomes epoxy glue upon addition of a hardener. Silicones prepare from silicone resins via room temperature vulcanization. Alkyd resins harden or cure by exposure to oxygen in the air. These industrial variants differ significantly from natural plant secretions. They serve as raw materials for paints and varnishes today. The word resin applies to nearly any component that sets into a hard finish. Nail polish serves as one common example of this modern application.
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Common questions
What are the main chemical components of plant resins?
Most plant resins are composed of terpenes including alpha-pinene and beta-pinene. These molecules form the backbone of the substance while smaller amounts contain tricyclic sesquiterpenes like longifolene.
Why do plants produce resin in response to injury?
Resins protect plants from insects and pathogens by flowing out when a tree trunk is cut or damaged. The liquid repels herbivores and stops bacteria from entering wounds while volatile phenolic compounds may attract predators of attacking insects.
When was the oldest known use of plant resins documented?
The oldest known use comes from the late Middle Stone Age in Southern Africa where people used it as an adhesive for hafting stone tools. Human use has been documented since ancient Greece with Theophrastus writing about these substances over two thousand years ago.
Which specific trees provide common examples of plant resins?
Examples include copal from Protium copal and Hymenaea courbaril, dammar gum from Dipterocarpaceae, and mastic from Pistacia lentiscus. Sandarac resin grows on Tetraclinis articulata which is the national tree of Malta while kauri gum comes from Agathis australis in New Zealand.
How are synthetic resins converted into solid materials today?
Many materials are produced via conversion of synthetic resins to solids such as Bisphenol A diglycidyl ether becoming epoxy glue upon addition of a hardener. Alkyd resins harden by exposure to oxygen in the air while silicones prepare from silicone resins via room temperature vulcanization.