Raphides ( ; singular ''raphide'' or ''raphis'') are needle-shaped crystals of calcium oxalate monohydrate ( prismatic

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

crystals) or

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

as aragonite ( dipyramidal orthorhombic crystals), found in more than 200 families of plants. Both ends are needle-like, but raphides tend to be blunt at one end and sharp 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 a 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 some 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 the 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 structures. Raphides typically occur in

parenchyma upright=1.6, Lung parenchyma showing damage due to large subpleural bullae. Parenchyma () is the bulk of functional substance in an animal organ such as the brain or lungs, or a structure such as a tumour. In zoology, it is the tissue that ...

cells in aerial organs, especially the leaves, and are generally confined to the mesophyll. As the leaf area increases, so does the number of raphides, the process starting in even young leaves. The first indication 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 idioblasts. Also, Electron micrographs have shown that raphide needle crystals 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 The hexagonal crystals reported by Wattendorf in ''

Agave americana ''Agave americana'', commonly known as the century plant, maguey, or American aloe, is a flowering plant species belonging to the family Asparagaceae. It is native to Mexico and the United States, specifically Texas. This plant is widely cultiv ...

'' were apparently calcium oxalate. Microscopy using polarized light shows bright opalescence with raphides. Plants like '' Tradescantia pallida'' also accumulate calcium oxalate crystals in response to heavy metals stress.

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 consuming animals, as they are likely to tear and harm the soft tissues of the throat or esophagus of an animal chewing on the plant's leaves. The venomous process is in two stages: mechanical pricking and injection of harmful

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products ...

. Typically ingestion of plants containing raphides, like those common in certain houseplants, can cause immediate numbing followed shortly by painful foot swelling, vesicle formation and swelling throat, 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. Plants containing large amounts of raphides are generally acrid and unpalatable. However, it is not always possible to detect the presence of raphides through taste alone. In some tubers such as the Indian turnip which contain large quantities of raphides, the roots are not unpalatable when cooked because the raphides are bound within a matrix of starch which prevents the tongue from sensing their presence. Some other plants store raphides in mucilaginous environments and also do not taste acrid. There is some doubt about the role of raphides in defense against herbivory. Insects are only rarely affected by them, and no more than by sand.

Ruminant Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microb ...

s are not harmed by them, because certain bacteria in their

rumen The rumen, also known as a paunch, is the largest stomach compartment in ruminants. The rumen and the reticulum make up the reticulorumen in ruminant animals. The diverse microbial communities in the rumen allows it to serve as the primary si ...

help to degrade oxalate.

Plants containing raphides

Common names vary. The following list is incomplete. Raphides are found in many species in the families

Araceae The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). Also ...

and Commelinaceae, but are also found in a few species in a number of other families.

Acanthaceae Acanthaceae () is a Family (biology), family (the acanthus family) of dicotyledonous flowering plants containing almost 250 genera and about 2500 species. Most are Tropics, tropical Herbaceous plant, herbs, shrubs, or twining vines; some are epip ...

: * '' Strobilanthes barbata'' (stem, leaf) * '' Strobilanthes callosa'' (stem, leaf) * '' Strobilanthes ciliata'' (stem, leaf) * '' Strobilanthes heyneana'' (leaf) * '' Strobilanthes integrifolia'' (stem, leaf) * '' Strobilanthes lupulina'' (stem, leaf) * '' Strobilanthes reticulata'' (stem, leaf) * '' Strobilanthes sessilis'' (stem, leaf) * '' Thunbergia erecta'' (stem, leaf) * '' Thunbergia laurifolia'' (stem, leaf)

Actinidiaceae The Actinidiaceae are a small family (biology), family of flowering plants. The family has three genus, genera and about 360 species and is a member of the order Ericales. Distribution They are temperate and subtropical woody plant, woody vines, ...

: * '' Actinidia arguta'' (root, flower, fruit) * ''

Actinidia callosa ''Actinidia callosa'', the Himalayan kiwi vine, is a species of flowering plant in the Chinese gooseberry family Actinidiaceae. A deciduous climber reaching , it is found in a wide variety of habitats at elevations from . Cultivated for its frui ...

'' (fruit) * ''

Actinidia chinensis ''Actinidia chinensis'' is a fruiting vine native to China. It is one of some 40 related species of the genus '' Actinidia'', and the origin of most commercial varieties of kiwifruit. There are three accepted varieties of the species. ''Actini ...

Beta Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...

'' * '' Spinacia''

Amaryllidaceae The Amaryllidaceae are a family of herbaceous, mainly perennial and bulbous (rarely rhizomatous) flowering plants in the monocot order Asparagales. The family takes its name from the genus '' Amaryllis'' and is commonly known as the amaryl ...

: * '' Crinum amabile'' (leaf) * '' Leucojum aestivum'' (leaf) * '' Pancratium sickenbergeri'' (leaf)

Monstera deliciosa ''Monstera deliciosa'', the Swiss cheese plant or split-leaf philodendron is a species of flowering plant native to tropical forests of southern Mexico, south to Panama. It has been introduced to many tropical areas, and has become a mildly invas ...

Thaumatophyllum speciosum ''Thaumatophyllum speciosum'' is a species of plant in the family Araceae, native to Brazil and Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features d ...

'' (flower) * '' Thaumatophyllum tweedianum'' (flower) * ''

Thaumatophyllum uliginosum ''Thaumatophyllum'' (formerly ''Philodendron#Modern classification, Meconostigma'') is a genus of flowering plants in the arum family, Araceae. Its species are native to northern (tropical) South America. Taxonomy The genus ''Thaumatophyllum'' ...

'' (flower) * '' Thaumatophyllum undulatum'' (flower) * '' Thaumatophyllum williamsii'' (flower) * '' Typhonium flagelliforme'' (stem) * '' Xanthosoma sagittifolium'' (root, stem, leaf) * '' Zantedeschia aethiopia'' (flower)

Araliaceae The Araliaceae are a family of flowering plants composed of about 43 genera and around 1500 species consisting of primarily woody plants and some herbaceous plants commonly called the ginseng family. The morphology of Araliaceae varies widely ...

: * '' Brassaia''

Arecaceae The Arecaceae () is a family (biology), family of perennial plant, perennial, flowering plants in the Monocotyledon, monocot order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, all commonly k ...

: * '' Acrocomia aculeata'' (root, leaf, flower) * '' Acrocomia crispa'' (root, leaf, flower) * '' Acrocomia emensis'' (root, leaf, flower) * '' Acrocomia glaucensis'' (root, leaf, flower) * '' Acrocomia hassleri'' (root, leaf, flower) * '' Acrocomia intumescens'' (root, leaf, flower) * '' Acrocomia totai'' (root, leaf, flower) * '' Allagoptera campestris'' (leaf) * '' Ammandra decasperma'' (pseudopedicel) * '' Aphandra natalia'' (pseudopedicel) * '' Archontophoenix alexandrae'' (embryo) * '' Areca catechu'' (embryo) * '' Areca macrocalyx'' (embryo) * '' Areca novohibernica'' (embryo) * '' Arenga tremula'' (embryo) * ''

Bactris gasipaes ''Bactris gasipaes'' is a species of Arecaceae, palm native to the tropical forests of Central America, Central and South America. It is well spread in these regions, where it is often cultivated by smallholders in agroforestry systems or more ...

'' (fruit) * '' Brassiophoenix dryomphloeides'' (embryo) * '' Butia buenopolensis'' (leaf, flower) * '' Butia campicola'' (leaf) * '' Butia capitata'' (leaf) * '' Butia catarinensis'' (leaf) * '' Butia exospadix'' (leaf) * '' Butia leptospatha'' (leaf) * '' Butia marmorii'' (leaf) * '' Butia microspadix'' (leaf) * '' Butia pubispatha'' (leaf) * '' Calyptrocalyx albertisianus'' (fruit) * '' Calyptrocalyx hollrungii'' (embryo) * '' Calyptrocalyx lepidotus'' (fruit) * '' Calyptrocalyx spicatus'' (embryo) * '' Caryota cumingii'' (embryo) * '' Caryota mitis'' (root, stem, leaf, flower, fruit) * '' Caryota rumphiana'' (stem, leaf) * '' Chamaedorea tepejilote'' (embryo) * '' Cocos nucifera'' (root, stem, leaf) * '' Copernicia tectorum'' (flower, fruit) * '' Cyrtostachys renda'' (embryo) * '' Drymophloeus pachycladus'' (embryo) * '' Drymophloeus subdistichus'' (embryo) * '' Dypsis decaryi'' (embryo) * '' Dypsis leptocheilos'' (embryo) * '' Dypsis lutescens'' (embryo) * '' Euterpe oleracea'' (embryo) * '' Howea fosteriana'' (fruit) * '' Hydriastele rostrata'' (embryo) * '' Hyophorbe verschaffeltii'' * '' Iguanura sp. (embryo) * '' Laccospadix australasicus'' (fruit) * '' Linospadix microcarya'' (fruit) * '' Linospadix monostachya'' (fruit) * '' Livistonia saribus'' (embryo) * '' Normanbya normanbyi'' (embryo) * '' Oenocarpus bacaba'' (embryo) * '' Oenocarpus bataua'' (embryo) * '' Oncosperma horridum'' (embryo) * '' Oncosperma tigillarium'' (embryo) * '' Pelagodoxa henryana'' (fruit) * '' Pinanga coronata'' (embryo) * '' Pinanga negrosensis'' (embryo) * '' Pinanga malaiana'' (embryo) * '' Pinanga scortechinii'' (embryo) * '' Prestoea acuminata'' (embryo) * '' Ptychosperma caryotoides'' (embryo) * '' Rhapis excelsa'' (embryo) * '' Solfia samoensis'' (embryo) Aspleniaceae: * '' Asplenium cardiophyllum'' (leaf epidermis)

Asparagaceae Asparagaceae (), known as the asparagus family, is a family of flowering plants, placed in the order Asparagales of the monocots. The family name is based on the edible garden asparagus, '' Asparagus officinalis''. This family includes both ...

: * '' Agave debilis'' (root, leaf) * '' Agave geminiflora'' (flower) * '' Agave gracillima'' (root, leaf) * '' Agave guerrerensis'' (root, stem, leaf) * '' Agave guttata'' (root, leaf) * '' Agave hauniensis'' (root, leaf) * '' Agave howardii'' (flower) * '' Agave longiflora'' (root, stem, leaf) * '' Agave multicolor'' (flower) * '' Agave nanchititlensis'' (root, leaf) * '' Agave neonelsonii'' (flower) * '' Agave parrasana'' (leaf) * '' Agave platyphylla'' (flower) * '' Agave polycantha'' (flower) * '' Agave potosina'' (root, stem, leaf) * '' Agave pratensis'' (root, leaf) * '' Agave scabra'' (root, leaf) * '' Agave singuliflora'' (root, leaf) * '' Agave stictata'' (root, leaf) * '' Agave tequilana'' (root, leaf) * '' Agave victoriae-reginae'' (leaf) * ''Bellevalia paradoxa'' (leaf) * '' Chlorophytum orchidastrum'' * '' Cordyline terminalis'' (root, stem, leaf) * '' Dracaena sanderiana'' (leaf) * '' Hyacinthella nervosa'' (leaf) * '' Hyacinthella hispida'' (leaf) * '' Hyacinthella siirtensis'' (leaf) * '' Hyacinthella venusta'' (leaf) * '' Ornithogalum alpiganum'' (stem, leaf) * '' Ornithogalum caudatum'' (flower) * '' Polygonatum odoratum'' (leaf) * '' Polygonatum prattii'' (leaf) * '' Triteleia crocea'' (ovary) * '' Triteleia dudleyi'' (ovary) * '' Triteleia hendersonii'' (ovary) * '' Triteleia hyacintha'' (ovary) * '' Triteleia ixioides'' (ovary) * '' Triteleia laxa'' (ovary) * '' Yucca treculiana'' (root) Asphodelaceae: * '' Aloe harlana'' (leaf) * '' Aloe nobilis'' (leaf) * '' Asphodelus aestivus'' (root) * '' Gasteria obliqua'' (leaf) * '' Haworthia cymbiformis'' (leaf)

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

: * '' Aster warmingii'' (root) * '' Baccharis glaziovii'' (stem) * '' Silybum marianum'' (stem) * '' Solidago chilensis'' (stem) Balsaminaceae: * '' Impatiens arguta'' (stem) * '' Impatiens balfourii'' (stem, leaf, flower) * '' Impatiens niamniamensis'' (stem) * '' Impatiens parviflora'' (flower) * '' Impatiens thomsonii'' (stem, leaf, flower)

Boraginaceae Boraginaceae, the Borago, borage or forget-me-not family, includes about 2,000 species of shrubs, trees, and herbs in 146 to 154 genus, genera with a worldwide distribution. The APG IV system from 2016 classifies the Boraginaceae as single famil ...

: * '' Onosma mollis'' (leaf) * '' Onosma sorgeri'' (leaf) Bromeliaceae: * very widespread

Cactaceae A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...

: * widespread

Colchicaceae Colchicaceae is a family of flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; ...

: * '' Colchicum kurdi'' (root) Commelinaceae: * '' Cochliostema odoratissimum'' (stem, leaf, flower) * '' Commelina coelestis'' (pollen) * '' Commelina tuberosa'' (pollen) * '' Dichorisandra thyrsiflora'' (anther) * '' Tinantia anomala'' (root, leaf, flower) * '' Tinantia pringlei'' (root, leaf, flower) * '' Tradescantia ohiensis'' (stem) * '' Tradescantia pallida'' (anther) * '' Tradescantia spathacea'' (anther) * '' Triceratella''

Cucurbitaceae The Cucurbitaceae (), also called cucurbits or the gourd family, are a plant family (biology), family consisting of about 965 species in 101 genera.

: * '' Momordica dioica'' (stem) * '' Momordica cochinchinensis'' (stem) Dioscoreaceae: * '' Dioscorea bulbifera'' (root, bulbil) * '' Dioscorea esculenta'' (root) * '' Dioscorea hispida'' (root, petiole) * '' Dioscorea japonica'' (root) * '' Dioscorea polystachya'' (root, stem) Ebenaceae: * '' Diospyros montana'' (bark, fruit)

Euphorbiaceae Euphorbiaceae (), the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of Euphorbia, the type genus of the family. Most spurges, such as ''Euphorbia paralias'', ar ...

: * '' Ricinus communis'' (leaf)

Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...

: * '' Acacia robeorum'' (stem, leaf) * '' Medicago truncatula'' (leaf) * '' Pachyrhizus tuberosus'' (root) Haemodoraceae: * '' Anigozanthos flavidus'' (leaf, flower) * '' Conostylis candicans'' (flower) Heliconiaceae: * '' Heliconia indica'' (root, flower, fruit) * '' Heliconia longiflora'' (leaf) Hydrangeaceae: * '' Hydrangea macrophylla'' (leaf)

Lamiaceae The Lamiaceae ( ) or Labiatae are a family (biology), family of flowering plants commonly known as the mint, deadnettle, or sage family. Many of the plants are aromatic in all parts and include widely used culinary herbs like basil (herb), ba ...

: * '' Satureja khuzestanica'' (leaf) Liliaceae: * '' Drimia maritima'' (leaf, flower bud) Lowiaceae: * '' Orchidantha maxillarioides'' (stem, leaf) Marcgraviaceae: * very widespread Musaceae: * ''

Musa acuminata ''Musa acuminata'' is a species of banana native to South Asia, Southern Asia, its range comprising the Indian subcontinent and Southeast Asia. Many of the modern edible dessert bananas are derived from this species, although some are hybrids wi ...

'' (leaf, fruit) * '' Musa ingens'' (leaf, flower) * '' Musa maclayi'' (leaf, flower, fruit) Nyctaginaceae: * '' Bougainvillea glabra'' (leaf) * '' Bougainvillea spectabilis'' (leaf) Oleaceae: * very widespread Onagraceae: * '' Epilobium tibetanum'' (leaf) * '' Ludwigia peploides'' (leaf)

Orchidaceae Orchids are plants that belong to the family (biology), family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan distribution, cosmopolitan plants that ...

: * very widespread Pandanaceae: * '' Pandanus dubius'' (wood) * '' Pandanus leram'' (leaf) * '' Pandanus tectorius'' (wood) Passifloraceae'': * '' Passiflora cincinnata'' (fruit) Philydraceae: * '' Heimholtzia glaberrima''

Piperaceae The Piperaceae (), also known as the pepper family, are a large family (biology), family of flowering plants. The group contains roughly 3,600 currently accepted species in five genera. The vast majority of species can be found within the two mai ...

Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...

: * '' Cenchrus echinatus''

Polygonaceae The Polygonaceae are a Family (biology), family of flowering plants known Common name, informally as the knotweed family or smartweed—buckwheat family in the United States. The Botanical name, name is Basionym, based on the genus ''Polygonum'', ...

: * '' Rheum rhabarbarum'' Pontederiaceae: * '' Monochoria africana'' (anther) * '' Pontederia cordata'' (root) * '' Pontederia crassipes'' (stem) Roridulaceae: * '' Roridula gorgonias'' (flower)

Rosaceae Rosaceae (), the rose family, is a family of flowering plants that includes 4,828 known species in 91 genera. The name is derived from the type genus '' Rosa''. The family includes herbs, shrubs, and trees. Most species are deciduous, but som ...

: * '' Rubus alutaceus'' (leaf)

Rubiaceae Rubiaceae () is a family (biology), family of flowering plants, commonly known as the coffee, madder, or bedstraw family. It consists of terrestrial trees, shrubs, lianas, or herbs that are recognizable by simple, opposite leaves with Petiole ( ...

: * very widespread Tetrameristaceae: * '' Pelliciera rhizophorae'' (stem, flower) * '' Pentamerista neotropica'' (flower) * '' Tetramerista glabra'' (stem) Typhaceae: * '' Typha angustifolia'' (leaf) * '' Typha latifolia'' (leaf)

Vitaceae The Vitaceae are a family of flowering plants, with 14 genera and around 910 known species, including common plants such as Vitis, grapevines (''Vitis'' spp.) and Parthenocissus quinquefolia, Virginia creeper (''Parthenocissus quinquefolia''). Th ...

: * '' Cissus alata'' (leaf) * '' Cissus discolor'' (leaf) * '' Cissus quadrangularis'' (leaf) * '' Cissus repanda'' (leaf) * '' Cissus rotundifolia'' (leaf) * '' Parthenocissus quinquefolia'' (leaf) * '' Parthenocissus tricuspidata'' (leaf) * '' Parthenocissus vitacea'' (leaf) * '' Rhoicissus tomentosa'' (leaf) * '' Tetrastigma voinierianum'' (leaf) * '' Vitis berlandieri'' (root) * '' Vitis rupestris'' (anther) * ''

Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean Basin, Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern ...

'' (leaf)

References

Bibliography

* See ''Supporting Information''. * * {{Cite journal , year=2004 , last=Keating , first=Richard C. , title=Systematic Occurrence of Raphide Crystals in Araceae. , url=https://www.jstor.org/stable/3298626 , journal=Annals of the Missouri Botanical Garden , language=en , volume=91 , issue=3 , pages=495–504 , jstor=3298626 Plant physiology Oxalate minerals Organic minerals Plant toxins

Calcium oxalate in plants

Harmful effects

Plants containing raphides

See also

References

Bibliography