Latex is a stable dispersion (emulsion) of polymer in an aqueous medium. It is found in nature, but synthetic latexes can be made by polymerization a monomer such as styrene that has been emulsion with .
Latex as found in nature is a milky fluid found in 10% of all flowering plants (angiosperms).
It is a complex emulsion consisting of , , , , Vegetable oil, , , and Natural gum that coagulation on exposure to air. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or scarlet latex. Since the 17th century, latex has been used as a term for the fluid substance in plants. It serves mainly as defense against herbivorous . Latex is not to be confused with plant sap; it is a separate substance, separately produced, and with separate functions.
The word latex is also used to refer to natural latex rubber, particularly non-vulcanization rubber. Such is the case in products like latex , latex and latex clothing.
Originally, the name given to latex by indigenous Equator tribes who cultivated the plant was “caoutchouc”, from the words “caa” (tear) and “ochu” (tree), because of the way it is collected.
The cells (
) in which latex is found make up the laticiferous system, which can form in two very different ways. In many plants, the laticiferous system is formed from rows of cells laid down in the meristem
of the Plant stem
between these cells are dissolved so that continuous tubes, called latex vessels, are formed. Since these vessels are made of many cells, they are known as articulated laticifers
. This method of formation is found in the Papaveraceae
and in the rubber
trees (Para rubber tree, members of the family Euphorbiaceae
, members of the Moraceae
, such as the Panama rubber tree Castilla elastica
), and members of the family Asteraceae
. For instance, Parthenium argentatum
the guayule plant, is in the tribe Heliantheae
; other latex-bearing Asteraceae with articulated laticifers include members of the Cichorieae
, a clade
whose members produce latex, some of them in commercially interesting amounts. This includes Taraxacum kok-saghyz
, a species cultivated for latex production.
In the Asclepiadaceae
families, on the other hand, the laticiferous system is formed quite differently. Early in the development of the seedling, latex cells differentiate, and as the plant grows these latex cells grow into a branching system extending throughout the plant. In many Euphorbiaceae
, the entire structure is made from a single cell – this type of system is known as a non-articulated laticifer
, to distinguish it from the multi-cellular structures discussed above. In the mature plant, the entire laticiferous system is descended from a single cell or group of cells present in the embryo
The laticiferous system is present in all parts of the mature plant, including roots, stems, leaf, and sometimes the . It is particularly noticeable in the cortical tissues. Latex is usually exuded as a white liquid, but is some cases it can be clear, yellow or red, as in Cannabaceae.
Latex is produced by 20,000 species from over 40 families
occurring in multiple lineages in both dicotyledonous
types of plant. It is also found in
. Among tropical plant species 14% create latex, as opposed to 6% of temperate plant species.
Several members of the fungal kingdom also produce latex upon injury, such as Lactarius deliciosus
and other lactarius
. This suggests it is the product of convergent evolution and has been selected for on many separate occasions.
Latex functions to protect the plant from herbivores. The idea was first proposed in 1887 by Joseph F. James, who noted that latex
carries with it at the same time such disagreeable properties that it becomes a better protection to the plant from enemies than all the thorns, prickles, or hairs that could be provided. In this plant, so copious and so distasteful has the sap become that it serves a most important purpose in its economy.
Evidence showing this defense function include the finding that
will eat leaves drained of their latex but not intact ones, that many insects sever the veins carrying latex before they feed, and that the latex of Asclepias humistrata
) kills by trapping 30% of newly hatched monarch butterfly caterpillars.
Other evidence is that latex contains 50–1000× higher concentrations of defense substances than other plant tissues. These toxins include ones that are also toxic to the plant and consist of a diverse range of chemicals that are either poisonous or "Antinutrient". Latex is actively moved to the area of injury; in the case of Cryptostegia grandiflora, this can be more than 70 cm.
The clotting property of latex is functional in this defense since it limits wastage and its stickiness traps insects and their mouthparts.
It has been noted that while there exist other explanations for the existence of latex including storage and movement of plant nutrients, waste, and maintenance of water balance that "essentially none of these functions remain credible and none have any empirical support".
The latex of many species can be processed to produce many materials.
Natural rubber is the most important product obtained from latex; more than 12,000 plant species yield latex containing rubber, though in the vast majority of those species the rubber is not suitable for commercial use.
This latex is used to make many other products including , , , , and .
Balatá and gutta percha latex contain an inelastic polymer related to rubber.
Latex from the chicle and Dyera costulata trees is used in chewing gum.
Dried latex from the opium poppy is called opium, the source of several useful , such as morphine, codeine and papaverine, as well as the street drug heroin.
Synthetic latexes are used in (e.g. latex paint) and because they solidify by coalescence of the polymer particles as the water evaporates, and therefore can form films without releasing potentially toxic organic solvents in the environment. Other uses include cement additives, and to conceal information on . Latex, usually styrene-based, is also used in .
Latex is used in many types of clothing
. Worn on the body (or applied directly by painting) it tends to be skin-tight, producing a "second skin" effect.
Some people only experience a Allergy
when exposed to latex, like eczema
, contact dermatitis or developing a rash
Others have a serious latex allergy, and exposure to latex products such as can cause anaphylactic shock
. Guayule latex has only 2% of the levels of protein found in Hevea latexes, and is being researched as a lower-allergen substitute. Additionally, chemical processes may be employed to reduce the amount of antigenic protein in Hevea latex, yielding alternative materials such as Vytex Natural Rubber Latex which provide significantly reduced exposure to latex allergens.
About half of people with spina bifida are also allergic to natural latex rubber, as well as people who have had multiple surgeries, and people who have had prolonged exposure to natural latex.
Several species of the microbe
, and Actinoplanes
are capable of consuming rubber latex.
However, the rate of biodegradation is slow, and the growth of bacteria utilizing rubber as a sole carbon source is also slow.