About Ricinus communis L.
Ricinus communis L., commonly known as the castor oil plant, varies greatly in growth habit and appearance. Breeding has increased this variability, with cultivars selected for specific leaf and flower colors and improved oil production. It is a fast-growing, suckering shrub that can grow to the size of a small tree, reaching around 12 metres (39 feet), but it is not cold hardy. Its glossy leaves are 15–45 centimetres (6–18 inches) long, long-stalked, alternate, and palmate with five to twelve deep, coarsely toothed lobes. In some varieties, young leaves start dark reddish purple or bronze and gradually turn dark green, sometimes with a reddish tinge, as they mature. The leaves of other varieties are green from the start, while in others a pigment masks green in all chlorophyll-bearing structures (leaves, stems, and young fruit), so these plants stay a striking purple to reddish-brown throughout their life. Dark-leaved and green-leaved plants can grow alongside each other, suggesting a single gene controls pigment production in some varieties. Stems and spherical, spiny seed capsules also vary in pigmentation. The fruit capsules of some varieties are more showy than the plant’s flowers. Flowers have no petals, are unisexual, with both male and female flowers growing on the same individual (monoecious), and are arranged in terminal panicle-like inflorescences that are green, or shades of red in some varieties. Male flowers are numerous, yellowish-green, with prominent creamy stamens. Female flowers grow at the tips of spikes, sit inside immature spiny capsules, are relatively few in number, and have prominent red stigmas. The fruit is a spiny, greenish to reddish-purple capsule that holds large, oval, shiny, bean-like, highly poisonous seeds with variable brownish mottling. Castor seeds have a warty appendage called the caruncle, a type of elaiosome that encourages seed dispersal by ants (myrmecochory). The fat-rich yellow nodule (caruncle) at one end of the seed is nutritious for young ants. After ants carry seeds back to their nests and remove the edible caruncle, they discard the rest of the seed in their trash piles, where the seed can germinate and grow into a new plant. This species reproduces via a mixed pollination system that favors selfing by geitonogamy, but can also out-cross via wind pollination (anemophily) or insect pollination (entomophily). Although R. communis is native to the southeastern Mediterranean Basin, Eastern Africa, and India, it is now widespread throughout tropical regions. In climates with suitable conditions, castor establishes itself easily and can become invasive, and it is often found growing on wasteland. Ricinus communis is the host plant of the common castor butterfly (Ariadne merione), the eri silkmoth (Samia cynthia ricini), and the castor semi-looper moth (Achaea janata). It is also used as a food plant by the larvae of some other Lepidoptera species, including Hypercompe hambletoni and the nutmeg moth (Discestra trifolii). The jumping spider Evarcha culicivora associates with this plant: the spiders eat its nectar, and preferentially use R. communis as a site for courtship. Ricinus is extremely allergenic, with an OPALS allergy scale rating of 10 out of 10. It is also a very strong trigger for asthma, and allergies to Ricinus are common and severe. The plant produces large amounts of very fine pollen that easily becomes airborne, can be inhaled into the lungs, and triggers allergic reactions. Plant sap causes skin rashes; people allergic to the plant can also develop rashes from touching leaves, flowers, or seeds. They may also have cross-allergic reactions to latex sap from the related rubber tree Hevea brasiliensis. Raw castor beans are toxic due to the presence of ricin, which is also found in lower concentrations throughout the entire plant. The lethal dose for adults is considered 4 to 8 seeds, though reports of actual poisoning are relatively rare. Guinness World Records lists this as the world's most poisonous common plant. If ricin is ingested, symptoms typically start within 2 to 4 hours, but may be delayed up to 36 hours. Symptoms include a burning sensation in the mouth and throat, abdominal pain, purging, and bloody diarrhea. Within several days, severe dehydration, low blood pressure, and decreased urine develop. Unless treated, death usually occurs within 3 to 5 days, but most cases make a full recovery. Poisoning occurs when animals, including humans, ingest broken castor beans or chew seeds to break them open; intact seeds may pass through the digestive tract without releasing toxin. Ricin gives the castor oil plant some natural protection from insect pests like aphids, and it has been investigated for potential use as an insecticide. Commercially produced cold-pressed castor oil is not toxic to humans in normal doses, whether used internally or externally. Castor oil plant is widely used as a decorative plant in parks and other public spaces, particularly as a "dot plant" in traditional bedding schemes. If sown early under glass and kept at around 20 °C (68 °F) until planted out, it can reach a height of 2–3 metres (6.6–9.8 ft) in one year. In frost-prone areas, it is usually shorter and grown as an annual. It can grow well outdoors in cooler climates, at least in southern England, and its leaves do not suffer frost damage in sheltered locations, where it remains evergreen. It was used in Edwardian-era parks in Toronto, Canada. It is not cultivated commercially in the United States, but grows wild there, notably in Griffith Park, Los Angeles. Global annual castor seed production is around two million tons. Leading production regions are India, which produces over three-quarters of the global yield, China, and Mozambique, and it is widely grown as a crop in Ethiopia. There are several active breeding programs for the species. Modern uses of natural, blended, or chemically modified castor products include: use as a non-freezing, antimicrobial, pressure-resistant lubricant for special applications, for either latex or metals, or as a lubricating component of fuels; use as a source of various chemical feedstocks; use as a raw material for some types of biodiesel; use to make attractively patterned, low-cost personal adornments such as non-durable necklaces and bracelets (holes must not be drilled in the seeds to make beads; the intact outer shell protects the wearer from poison, but wearing castor beans has been known to cause rashes and more severe reactions); use as a component of many cosmetics; use as an antimicrobial; the high percentage of ricinoleic acid residues in castor oil and its derivatives inhibits many viruses, bacteria, and fungi, making these products useful components of ointments and similar preparations; use as the main raw material (in oil form) for polyglycerol polyricinoleate, a modifier that improves the flow properties of cocoa butter in chocolate bar manufacturing, reducing production costs; and use as a repellent for moles and voles in lawns. Extract of Ricinus communis has shown acaricidal and insecticidal activity against adult Haemaphysalis bispinosa ticks and the hematophagous fly Hippobosca maculata. Members of the Bodo tribe of Bodoland in Assam, India, use the plant’s leaves to feed the larvae of muga and endi silkworms. Castor oil works as an effective motor lubricant and has been used in internal combustion engines, including World War I airplane engines, some racing car engines, and some model airplane engines. It was historically popular for lubricating two-stroke engines due to its higher heat resistance compared to petroleum-based oils. It does not mix well with petroleum products, especially at low temperatures, but mixes better with the methanol-based fuels used in glow model engines. In total-loss-lubrication applications, it tends to leave carbon deposits and varnish inside the engine, and it has been largely replaced by more stable, less toxic synthetic oils. Ricinus communis leaves are used for botanical printing (also called ecoprinting) in Asia; when bundled with cotton or silk fabric and steamed, the leaves leave a green imprint. In traditional Nigerian cuisine, fermented and carefully detoxified castor bean paste is made into the spice ogiri, used to flavor soups. Castor seeds have been found in Egyptian tombs dating back to 4000 BC, where the slow-burning oil was mostly used to fuel lamps. Herodotus and other Greek travellers recorded use of castor seed oil for lighting, body ointments, and improving hair growth and texture. Cleopatra is reputed to have used it to brighten the whites of her eyes. The Ebers Papyrus, an ancient Egyptian medical treatise dated to 1552 BC and translated in 1872, describes castor oil as a laxative. Use of castor bean oil (called eranda) in India has been documented since 2000 BC, for use in lamps and in local medicine as a laxative, purgative, and cathartic in Unani, Ayurvedic, siddha, and other ethnomedical systems. Traditional Ayurvedic and siddha medicine consider castor oil the most powerful medicinal for treating arthritic diseases, and it is regularly given to children to treat parasitic worm infections. The ancient Romans had a variety of medicinal and cosmetic uses for both the seeds and leaves of Ricinus communis. Naturalist Pliny the Elder noted the poisonous properties of the seeds, but wrote that they could be used to form wicks for oil lamps, and the oil used as a laxative and lamp oil. He also recommended topical uses for the leaves: applied with vinegar for erysipelas; used fresh on its own for breast diseases and fluxions; a decoction in wine with polenta and saffron for various inflammations; and boiled alone and applied to the face for three consecutive days to improve complexion. In Haiti, the plant is called maskreti, and it is processed into a red oil that is given to newborns as a purgative to cleanse their insides after their first bowel movements. Castor seed and its oil have also been used in Chinese local medicine for centuries, prescribed for internal use or use in wound dressings. Castor oil was used as an instrument of coercion by the paramilitary Blackshirts under Italian dictator Benito Mussolini, and by the Spanish Civil Guard in Francoist Spain. Dissidents and regime opponents were forced to ingest large amounts of the oil, triggering severe diarrhea and dehydration that could ultimately cause death. This punishment method was originally developed by Gabriele D'Annunzio, an Italian poet and Fascist supporter, during the First World War.
