Raphides
Encyclopedia
Raphides are needle-shaped crystals of calcium oxalate
as the monohydrate or calcium carbonate
as aragonite, found in more than 200 families of plants.
Both ends are needle-like, but raphides tend to be more blunt at one end and more tapering at the other.
Raphides are found in specialized plant cells or crystal chambers called idioblast
s. Electron micrographs have shown that raphide needle cystals are normally four sided or H-shaped (with a groove down both sides) or with a hexagonal cross section and some are barbed. Wattendorf (1976) suggested that all circular sectioned raphides, as visible in a light microscope, are probably hexagonal in cross section Microscopy using polarized light shows bright opalescence with raphides.
, vesicle formation and dysphagia
accompanied by painful stinging and burning to the mouth and throat with symptoms occurring for up to two weeks. Airway assessment and management are of the highest priority, as are extensive irrigation and analgesics in eye exposure.
Raphides cannot normally be destroyed by boiling; that requires an acidic environment or chemical solvents like ether, but heating raphide containing plant materials (like tubers) can fix the raphides into a dried starchy matrix so they are no longer mobile and thus less harmful. Some other plants store raphides in mucilaginous environments and also do not taste acrid.
Calcium oxalate
Calcium oxalate is a chemical compound that forms needle-shaped crystals, known in plants as raphides. A major constituent of human kidney stones, the chemical is also found in beerstone, a scale that forms on containers used in breweries...
as the monohydrate or calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
as aragonite, found in more than 200 families of plants.
Both ends are needle-like, but raphides tend to be more blunt at one end and more tapering at the other.
Calcium oxalate in plants
Many plants accumulate calcium oxalate crystals in response to surplus calcium, which is found throughout the natural environment. The crystals are produced in an intriguing variety of shapes. The crystal morphology depends on the taxonomic group of the plant. In one study of over 100 species, it was found that calcium oxalate accounted for 6.3% of plant dry weight. Crystal morphology and the distribution of raphides (in roots or leaves or tubers etc.) is similar in same taxa but different in others leaving possible opportunities for plant key characteristics and systematic identification; mucilage in raphide containing cells makes light microscopy difficult, though. Little is known about the mechanisms of sequestration or indeed the reason for accumulation of raphides but it is most likely as a defense mechanism against herbivory. It has also been suggested that in some cases raphides may help form plant skeletal structure. Raphides typically occur in parenchyma cells in aerial organs especially the leaves, and are generally confined to the mesophyl. As the leaf area increases, so does the number of raphides, the process starting in even young leaves. The first indications that the cell will contain crystals is shown when the cells enlarge with a larger nucleus.Raphides are found in specialized plant cells or crystal chambers called idioblast
Idioblast
Idioblasts are isolated plant cells which differ from neighboring tissues and contain non-living substances. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin, tannin or pigments etc...
s. Electron micrographs have shown that raphide needle cystals are normally four sided or H-shaped (with a groove down both sides) or with a hexagonal cross section and some are barbed. Wattendorf (1976) suggested that all circular sectioned raphides, as visible in a light microscope, are probably hexagonal in cross section Microscopy using polarized light shows bright opalescence with raphides.
Harmful effects
Raphides can produce severe toxic reactions by facilitating the passage of toxin through the herbivore's skin when the tissue containing the raphides also contains toxins. The lethal dose to mice is around 15 mg/kg. Raphides seem to be a defense mechanism against plant predators, as they are likely to tear and harm the soft tissues of the throat or esophagus of a plant predator chewing on the plant's leaves. The venomous process is in two stages: mechanical pricking and injection of harmful protease. Typically ingestion of plants containing raphides, like those common in certain houseplants, can cause painful edemaEdema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
, vesicle formation and dysphagia
Dysphagia
Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....
accompanied by painful stinging and burning to the mouth and throat with symptoms occurring for up to two weeks. Airway assessment and management are of the highest priority, as are extensive irrigation and analgesics in eye exposure.
Raphides cannot normally be destroyed by boiling; that requires an acidic environment or chemical solvents like ether, but heating raphide containing plant materials (like tubers) can fix the raphides into a dried starchy matrix so they are no longer mobile and thus less harmful. Some other plants store raphides in mucilaginous environments and also do not taste acrid.
Plants containing raphides
Common names vary. The following list is incomplete.- AlocasiaAlocasiaAlocasia is a genus of broad-leaved rhizomatous or tuberous perennials from the Family Araceae. There are 78 species of Alocasia occurring in Tropical & Subtropical Asia to Eastern Australia and widely cultivated in Oceania and South America. The large cordate or sagittate leaves grow to a length...
(Baibing in NE India) - ArisaemaArisaemaArisaema is a genus of about 150 species in the flowering plant family Araceae, native to eastern and central Africa, Asia and eastern North America. Its species are often called Cobra lilies, particularly the Asiatic species...
(Cobra Lily) - ArumArumArum is a genus of about 25 species of flowering plants in the family Araceae, native to Europe, northern Africa, and western Asia, with the highest species diversity in the Mediterranean region....
(Cuckoopint) - Brassaia (Umbrella Tree)
- CaladiumCaladiumCaladium is a genus of flowering plants in the family Araceae. They are often known by the common name elephant ear , Heart of Jesus, and Angel Wings...
(Angel wings) - CaryotaCaryotaCaryota is a genus of palm trees. They are often known as fishtail palms because of the shape of their leaves. There are about 13 species native to Asia and the South Pacific. One of the more widely known species is Caryota urens, which yields sap used to make an unrefined sugar called jaggery, and...
(Fishtail Palm) - ColocasiaColocasiaColocasia is a genus of 25 or more species of flowering plants in the family Araceae, native to tropical Polynesia and southeastern Asia. Common names include Elephant-ear, Taro, Cocoyam, Dasheen,Chembu, and Eddoe...
(Taro, Cocoyam, Eddoe) - DieffenbachiaDieffenbachiaDieffenbachia is a genus of tropical plants in the Family Araceae noted for their patterned leaves. Members of this genus are popular as houseplants because of their tolerance for shade. The common name is "dumb cane" due to its poisoning effect on the throat due to raphides...
(Dumb Cane) - EpipremnumEpipremnumEpipremnum is a genus of sub-tropical plants that is a perennial vine, that is often confused with other Monstereae such as Rhaphidophora aurea Birdsey. All parts of the plants are toxic, mostly due to trichosclereids and raphides. The species may have originated in Southeast Asia...
(Devil's Ivy, Pothos) - FuchsiaFuchsiaFuchsia is a genus of flowering plants that consists mostly of shrubs or small trees. The first, Fuchsia triphylla, was discovered on the Caribbean island of Hispaniola in 1703 by the French Minim monk and botanist, Charles Plumier...
(Fuchsia) - MonsteraMonsteraMonstera is a genus of about 60 species of flowering plants in the family Araceae, native to tropical regions of the Americas. The genus is named from the Latin word for "monstrous" or "abnormal", the members of the genus are distinguished by their unusual leaves with natural holes.They are herbs...
(Swiss Cheese Plant) - PhilodendronPhilodendronPhilodendron is a large genus of flowering plants in the Araceae family, consisting of close to 900 or more species according to TROPICOS . Other sources quote different numbers of species. According to S.J. Mayo there are about 350-400 formally recognized species whereas according to Croat there...
(Elephant Ears) - SpathiphyllumSpathiphyllumSpathiphyllum is a genus of about 40 species of monocotyledonous flowering plants in the family Araceae, native to tropical regions of the Americas and southeastern Asia. Certain species of Spathiphyllum are commonly known as Spath or Peace Lilies.They are evergreen herbaceous perennial plants with...
(Peace Lily) - SpinaciaSpinaciaSpinacia is the spinach genus.-External links:*...
(Spinach) - TradescantiaTradescantiaTradescantia , the Spiderworts, is a genus of an estimated 71 species of perennial plants in the family Commelinaceae, native to the New World from southern Canada south to northern Argentina. They are weakly upright to scrambling plants, growing to 30–60 cm tall, and are commonly found...
(Wandering Jew)