Ricinus
Ricinus communis, the castor bean or castor oil plant, is a species of perennial flowering plant in the spurge family, Euphorbiaceae. It is the sole species in the monotypic genus, Ricinus, and subtribe, Ricininae.
Its seed is the castor bean, which despite the term is not a bean. Castor is indigenous to the southeastern Mediterranean Basin, East Africa, and India, but is widespread throughout tropical regions.
Castor seed is the source of castor oil, which has a wide variety of uses. The seeds contain 40–60% oil that is rich in triglycerides, mainly ricinolein. The seed also contains ricin, a highly potent water-soluble toxin.
Description
Ricinus communis can vary greatly in its growth habit and appearance. The variability has been increased by breeders who have selected a range of cultivars for leaf and flower colours, and for oil production. It is a fast-growing, suckering shrub that can reach the size of a small tree, around, but it is not cold hardy.The glossy leaves are long, long-stalked, alternate and palmate with five to twelve deep lobes with coarsely toothed segments. In some varieties they start off dark reddish purple or bronze when young, gradually changing to a dark green, sometimes with a reddish tinge, as they mature. The leaves of some other varieties are green practically from the beginning, whereas in yet others a pigment masks the green color of all the chlorophyll-bearing parts, leaves, stems and young fruit, so that they remain a dramatic purple-to-reddish-brown throughout the life of the plant. Plants with the dark leaves can be found growing next to those with green leaves, so there is most likely only a single gene controlling the production of the pigment in some varieties. The stems and the spherical, spiny seed capsules also vary in pigmentation. The fruit capsules of some varieties are more showy than the flowers.
The flowers lack petals and are unisexual where both types are borne on the same plant in terminal panicle-like inflorescences of green or, in some varieties, shades of red. The male flowers are numerous, yellowish-green with prominent creamy stamens; the female flowers, borne at the tips of the spikes, lie within the immature spiny capsules, are relatively few in number and have prominent red stigmas.
The fruit is a spiny, greenish capsule containing large, oval, shiny, bean-like, highly poisonous seeds with variable brownish mottling. Castor seeds have a warty appendage called the caruncle, which is a type of elaiosome. The caruncle promotes the dispersal of the seed by ants.
It reproduces with a mixed pollination system which favors selfing by geitonogamy but at the same time can be an out-crosser by anemophily or entomophily.
Chemistry
Three terpenoids and a tocopherol-related compound have been found in the aerial parts of Ricinus. Compounds named -19-hydroxycasba-3,7,11-trien-5-one, 6α-hydroxy-10β-methoxy-7α,8α-epoxy-5-oxocasbane-20,10-olide, 15α-hydroxylup-20-en-3-one, and -3,4,4a,8a-tetrahydro-4a-hydroxy-2,6,7,8a-tetramethyl-2--2H-chromene-5,8-dione were isolated from the methanol extracts of Ricinus communis by chromatographic methods.Partitioned h-hexane fraction of Ricinus root methanol extract resulted in enrichment of two triterpenes: lupeol and urs-6-ene-3,16-dione. Crude methanolic extract, enriched n-hexane fraction and isolates at doses 100 mg/kg p.o. exhibited significant anti-inflammatory activity in carrageenan-induced hind paw oedema model.
Taxonomy
The evolution of castor and its relation to other species are currently being studied using modern genetic tools.The plant known as "false castor oil plant", Fatsia japonica, is not closely related.
Etymology
used the name Ricinus because it is a Latin word for tick; the seed is named so because of its bump at the tip as well as the markings borne that resemble certain ticks. The genus Ricinus also exists in zoology, and designates insects which are parasites of birds; this is possible because the names of animals and plants are governed by different nomenclature codes.The common name "castor oil" probably comes from its use as a replacement for castoreum, a perfume base made from the dried perineal glands of the beaver. It has another common name, palm of Christ, or Palma Christi, that derives from castor oil's reputed ability to heal wounds and cure ailments.
Distribution and habitat
Although R. communis is indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India, today it is widespread throughout tropical regions. In areas with a suitable climate, castor establishes itself easily where it can become an invasive plant and can often be found on wasteland.Ecology
Ricinus communis is the host plant of the common castor butterfly, the eri silkmoth, and the castor semi-looper moth. It is also used as a food plant by the larvae of some other species of Lepidoptera, including Hypercompe hambletoni and the nutmeg. A jumping spider Evarcha culicivora has an association with R. communis. They consume the nectar for food and preferentially use these plants as a location for courtship.Each castor seed has a yellow nodule full of fats one end of the seed that are nutritious for young ants. After hauling their harvest into their nests and pulling off the delicious part, ants discard the rest of the seed into their trash pile, where the future plant starts to grow.
Cultivation
It is also used extensively as a decorative plant in parks and other public areas, particularly as a "dot plant" in traditional bedding schemes. If sown early, under glass, and kept at a temperature of around until planted out, the castor oil plant can reach a height of in a year. In areas prone to frost it is usually shorter, and grown as if it were an annual. However, it can grow well outdoors in cooler climates, at least in southern England, and the leaves do not appear to suffer frost damage in sheltered spots, where it remains evergreen. It was used in Edwardian times in the parks of Toronto, Canada. Although not cultivated there, the plant grows wild in the US, notably Griffith Park in Los Angeles.Cultivars
s have been developed by breeders for use as ornamental plants and for commercial production of castor oil.;Ornamental cultivars
- 'Carmencita' has gained the Royal Horticultural Society's Award of Garden Merit
- 'Carmencita Bright Red' has red stems, dark purplish leaves and red seed pods;
- 'Carmencita Pink' has green leaves and pink seed pods
- 'Gibsonii' has red-tinged leaves with reddish veins and bright scarlet seed pods
- 'New Zealand Purple' has plum colored leaves tinged with red, plum colored seed pods turn to red as they ripen
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- 'Impala' is compact with reddish foliage and stems, brightest on the young shoots
- 'Red Spire' is tall with red stems and bronze foliage
- 'Zanzibarensis' is also tall, with large, mid-green leaves that have white midribs
- 'Hale' was launched in the 1970s for the US state of Texas. It is short and has several racemes
- 'Brigham' is a variety with reduced ricin content adapted for Texas, US. It grows up to and has 10% of the ricin content of 'Hale'
- 'BRS Nordestina' was developed by Brazil's Embrapa in 1990 for hand harvest and semi-arid environments
- 'BRS Energia" was developed by Embrapa in 2004 for mechanised or hand harvest
- 'GCH6' was developed by Sardarkrushinagar Dantiwada University, India, 2004: it is resistant to root rot and tolerant to fusarium wilt
- 'GCH5' was developed by Sardarkrushinagar Dantiwada University, 1995. It is resistant to fusarium wilt
- 'Abaro' was developed by the Ethiopian Institute of Agricultural Research's Essential Oils Research Center for hand harvest
- 'Hiruy' was developed by the Ethiopian Institute of Agricultural Research's Melkassa and Wondo Genet Agricultural Research Centers for hand harvest during 2010/2011
Allergenicity and toxicity
The castor oil plant produces abundant amounts of very light pollen, which easily become airborne and can be inhaled into the lungs, triggering allergic reactions. The sap of the plant causes skin rashes. People who are allergic to the plant can also develop rashes from touching the leaves, flowers, or seeds. They can also have cross-allergic reactions to latex sap from the related Hevea brasiliensis plant.
The toxicity of raw castor beans is due to the presence of ricin. Although the lethal dose in adults is considered to be four to eight seeds, reports of actual poisoning are relatively rare. According to the Guinness World Records, this is the world's most poisonous common plant. Ricin is also present in lower concentrations throughout the plant.
If ricin is ingested, symptoms commonly begin within two to four hours, but may be delayed by up to 36 hours. These include a burning sensation in mouth and throat, abdominal pain, purging and bloody diarrhea. Within several days there is severe dehydration, a drop in blood pressure and a decrease in urine. Unless treated, death can be expected to occur within 3–5 days; however, in most cases a full recovery can be made.
Poisoning occurs when animals, including humans, ingest broken castor beans or break the seed by chewing: intact seeds may pass through the digestive tract without releasing the toxin. The toxin provides the castor oil plant with some degree of natural protection from insect pests such as aphids. Ricin has been investigated for its potential use as an insecticide.
Commercially available cold-pressed castor oil is not toxic to humans in normal doses, whether internal or external.