Overview of Lauraceae

Lauraceae or laurel is a plant family that includes true laurel and its close relatives.The family includes about 2850 known species worldwide in about 45 genera (Christenhusz & Byng 2016).They are dicotyledonous plants mainly found in warm temperate and tropical regions, especially Southeast Asia and South America.Many are fragrant evergreen trees or shrubs, but some, such as sassafras, are deciduous, or include both deciduous and evergreen trees and shrubs, especially in tropical and temperate climates. The genus Cassytha is unique in the Lauraceae family because its members are parasitic vines.Most laurels are highly poisonous.

Overview

The family is distributed globally in tropical and warm climates.Lauraceae are important components of tropical forests from lowlands to mountains.In several forest areas, the number of species of Lauraceae ranks among the top five.Lauraceae gets its name from the habitat known as a laurel forest, where there are many trees that superficially resemble Lauraceae, although they may belong to other plant families such as Magnoliaceae or Myrtaceae.Laurel groves of various types can be found on most continents and on many major islands.Although the taxonomy of Lauraceae has not been determined, it is conservatively estimated that there are about 52 genera worldwide, including 3,000 to 3,500 species.Compared with other plant families, the taxonomy of Lauraceae is still poorly understood.This is due in part to its enormous diversity, difficulties in identifying species, and in part to underinvestment in taxonomic efforts.Recent monographs on small and medium genera (up to about 100 species) in Lauraceae have revealed many new species.A similar increase in the number of species identified in other larger genera is expected.

Description

Most Lauraceae plants are evergreen trees in habit.Exceptions include about two dozen Cassytha species, all of which are obligate parasitic vines.The fruit of plants in the Lauraceae family is a drupe, a single-seeded fleshy fruit with a hard layer, the endocarp, surrounding the seed.However, the endocarp is very thin, so the fruit resembles a single-seeded berry.The fruit of some species (notably the Ocotea genus) is partly submerged or covered in a cup-shaped or deep case formed by the calyx tube where the peduncle joins the fruit; this gives the fruit the appearance of an acorn.In some Lindera species, the base of the fruit has a peel.

Distribution and uses

Because the family is so ancient and distributed so widely across the supercontinent of Gondwana, modern species often occur in surviving populations isolated by geographical barriers, such as islands or tropical mountains.Relic forests preserve endemic flora and fauna in the community, which is of great value for inferring paleontological succession and climate change after the breakup of supercontinents.Many Lauraceae plants contain high concentrations of essential oils, some of which are used as fragrances and perfumes.In plants, most of these substances are components of irritating or poisonous sap or tissues that repel or poison many herbivorous or parasitic organisms.Some essential oils are used as fragrances, such as in the traditional laurel wreaths of the classical period, or in cabinetmaking, where aromatic woods are prized for insect repellent furniture chests.

• Some are valuable in cooking, eg bay leaf is a common ingredient in European, American and Asian cuisines.

• Avocados are important oily fruits grown in warm climates around the world.

• Many species are exploited for wood.

• Some species are valuable as sources of medicinal materials.

These genera include some of the most famous species of exceptional commercial value:

• Cinnamon: cinnamon, cinnamon and camphor laurel

• Laurus: laurel tree

• Persea: Habitat loss for avocados and overexploitation of this product has put many species at risk of extinction due to over-logging, massive illegal logging and habitat conversion.Conversely, some species, while commercially valuable in some countries, are considered invasive in others.For example, camphor tree, although a valuable ornamental and medicinal plant, has been declared a weed in subtropical forest areas of South Africa.