If you ever pluck a leaf or flower or cut any branches of certain angiosperms, you will find a white milky solution coming out of the cut stem. This white solution is called latex. It is defined as the dispersion of several microparticles of different polymers in water. The latex chemical compound occurs in several sources in nature and can also be synthesized in laboratories and industries. For example, rubber is a form of latex that is routinely produced in industries.
Natural Sources of Latex
More than 10% of all angiosperms produce latex. This percentage surmounts to around 20,000 flowering plants belonging to more than 40 families. Both dicot and monocot plants produce latex. Around 14 percent of tropical plants and 6 percent of temperate plant species produce and use latex. Some of the plant families that produce latex include Asclepiadoideae, Apocynaceae, Euphorbiaceae, Sapotaceae, Moraceae, Asteraceae, and Papaveraceae. For example, the opium poppy plant is the major source of opium and morphine.
You will also find some fungal species to produce latex when it experiences an injury. Examples of such fungus are Lactarius deliciosus and related milk-cap fungi.
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Role of Latex in Plants
Latex has defined defense function in plants. It protects the plants from several herbivores. Several studies have shown that slugs prefer to eat leaves from where latex is drained off. However, they prefer to avoid the intact leaves. It is considered a better protection mechanism than other means like hairs, prickles, and thorns. The latex of the sandhill milkweed plant can trap and kill newly hatched caterpillars of the monarch caterpillar.
Several studies have been conducted to look into the ingredients of the latex of different plants. From these studies, it was observed that latex contains around 50-1000X higher concentrations of different defense proteins and other substances compared to other plant tissues. Sometimes, latex contains compounds that can prove to be toxic to the parent plant. However, these toxins are effectively compartmentalized in the plant body. They can also prove to be antinutritive for the plant.
Latex also displays unique clotting properties. For example, in the plant Cryptostegia grandiflora, the latex rushes to the site of injury to clot the wound. As a result, it limits wastage of plant sap and other products and traps the insects' mouthparts due to its stickiness.
Latex is also considered a medium for the movement and storage of plant nutrients like sugar, salt, alkaloids, tannin, enzymes, plant waste, etc. It is also believed to be involved in maintaining the water concentration in different plant parts. It enables the complex mixing of different substances like waxes, fats, resins, gums, etc. The latex chemical compound moves into the circulation and travels longitudinally. Thus it helps in conducting different substances from one part to another.
Latex also acts as an excretory reservoir for different plant products. The plant excretes several waste products into the latex solution.
Application of Latex in Our Daily Lives
Latex has found several applications in our daily lives. The most commonly used latex is that obtained from the rubber industry. Around 12000 species of plants produce latex that contains rubber. However, most of these rubber thus obtained are not deemed suitable for commercial uses. Such rubber is used to make different products like tires, rubber bands, grips of bat, mattresses, gloves, balloons, swimming caps, to health care products like condoms and catheters. The gutta percha and balata latex resemble the rubber latex as it contains an inelastic polymer.
Chewing gum is another important contribution of plant latex. Most people have used such gums in their daily life. Many companies have started injecting compounds of medicinal values into these chewing gums. The basis of such chewing gum is the jelutong and chicle tree latex.
As stated earlier, the dried latex obtained from opium poppy seeds is known as opium. Opium is the source of several alkaloids with analgesic properties like thebaine, codeine, and morphine. Some of these opioids are used to make stronger variants of them. The latex also contains non-analgesic alkaloids like noscapine and papaverine.
Latex has also been used for clothing purposes. The cloth sticks to the skin and produces the effect of a second skin. Several people around the world wear such latex-based clothing.