- 19th-century illustration
- Vertically growing specimen
- Specimen in Chino, California
- Flowers
- Seed heads in late summer
Conium maculatum | |
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Conium maculatum in California | |
Scientific classification ![]() | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Apiales |
Family: | Apiaceae |
Genus: | Conium |
Species: | C. maculatum |
Binomial name | |
Conium maculatum L., 1753 | |
Synonyms [1] | |
List
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Conium maculatum, known as hemlock (British English), [2] or poison hemlock (American English) [3] is a highly poisonous flowering plant in the carrot family Apiaceae, native to Europe and North Africa. It is herbaceous without woody parts and has a biennial lifecycle. A hardy plant capable of living in a variety of environments, hemlock is widely naturalised in locations outside its native range, such as parts of Australia, West Asia, and North and South America, to which it has been introduced. It is capable of spreading and thereby becoming an invasive weed.
All parts of the plant are toxic, especially the seeds and roots, and especially when ingested. Under the right conditions the plant grows quite rapidly during the growing season and can reach heights of 2.4 metres (8 feet), with a long penetrating root. The plant has a distinctive odour usually considered unpleasant that carries with the wind. The hollow stems are usually spotted with a dark maroon colour and become dry and brown after completing its biennial lifecycle. The hollow stems of the plant are deadly for up to three years after the plant has died. [4]
Conium maculatum is a herbaceous flowering plant that grows to 1.5–2.5 metres (5–8 feet) tall, exceptionally 3.6 m (12 ft). [5] All parts of the plant are hairless (glabrous). Hemlock has a smooth, green, hollow stem, usually spotted or streaked with red or purple. The leaves are two- to four-pinnate, finely divided and lacy, overall triangular in shape, up to 50 centimetres (20 inches) long and 40 cm (16 in) broad. [6] Hemlock's flower is small and white; they are loosely clustered and each flower has five petals. [7]
A biennial plant, hemlock produces leaves at its base the first year but no flowers. In its second year it produces white flowers in umbrella-shaped clusters. [8]
Hemlock can be confused with the wild carrot plant ( Daucus carota , sometimes called Queen Anne's lace). Wild carrot has a hairy stem without purple markings, and grows less than 1 m (3+1⁄2 ft) tall. [9] One can distinguish the two from each other by hemlock's smooth texture, vivid mid-green colour, purple spotting of stems and petioles and typical height of the flowering stems being at least 1.5 m (5 ft) twice the maximum for wild carrot. Wild carrots have hairy stems that lack the purple blotches. [10] [11] The species can also be confused with harmless cow parsley ( Anthriscus sylvestris, also sometimes called Queen Anne's lace). [8] [12]
The plant should not be visually confused with the North American-native Tsuga , a coniferous tree sometimes called the hemlock, hemlock fir, or hemlock spruce, from a slight similarity in the leaf smell. The ambiguous shorthand of 'hemlock' for this tree is more common in the US dialect than the plant it is actually named after.[ citation needed ] Similarly, the plant should not be confused with Cicuta (commonly known as water hemlock). [12]
The genus name "Conium" refers to koneios, the Greek word for 'spin' or 'whirl', alluding to the dizzying effects of the plant's poison after ingestion. In the vernacular, "hemlock" most commonly refers to the species C. maculatum. Conium comes from the Ancient Greek κώνειον – kṓneion: "hemlock". This may be related to konas (meaning to whirl), in reference to vertigo, one of the symptoms of ingesting the plant. [13]
C. maculatum, also known as poison hemlock, was the first species within the genus to be described. It was identified by Carl Linnaeus in his 1753 publication, Species Plantarum. Maculatum means 'spotted', in reference to the purple blotches characteristic of the stalks of the species. [14]
Vernacular names in the English language are hemlock (British English), poison hemlock (American English), poison parsley, spotted corobane (rarer forms), carrot fern (Australian Eng.), devil's bread or devil's porridge (Irish Eng.) [15]
The hemlock plant is native to Europe and the Mediterranean region. [16]
It exists in some woodland (and elsewhere) in most British Isles counties; [17] in Ulster these are particularly County Down, County Antrim and County Londonderry. [18]
It has become naturalised in Asia, North America, Australia and New Zealand. [19] [20] [15] It is sometimes encountered around rivers in southeast Australia and Tasmania. [21] Infestations and human contact with the plant are sometimes newsworthy events in the U.S. due to its extreme toxicity. [22] [23]
The plant is often found in poorly drained soil, particularly near streams, ditches, and other watery surfaces. It also appears on roadsides, edges of cultivated fields, and waste areas. [19] Conium maculatum grows in quite damp soil, [2] but also on drier rough grassland, roadsides and disturbed ground. It is used as a food plant by the larvae of some lepidoptera, including silver-ground carpet moths and particularly the poison hemlock moth ( Agonopterix alstroemeriana ). The latter has been widely used as a biological control agent for the plant. [24] Hemlock grows in the spring, when much undergrowth is not in flower and may not be in leaf. All parts of the plant are poisonous. [3]
Hemlock contains coniine and some similar poisonous alkaloids, and is poisonous to all mammals (and many other organisms) that eat it. Intoxication has been reported in cattle, pigs, sheep, goats, donkeys, rabbits, and horses. Ingesting more than 150–300 milligrams of coniine, approximately equivalent to six to eight hemlock leaves, can be fatal for adult humans. [25] The seeds and roots are more toxic than the leaves. [26] Farmers also need to ensure that the hay fed to their animals does not contain hemlock. Hemlock is most poisonous in the spring when the concentration of γ-coniceine (the precursor to other toxins) is at its peak. [27] [28]
C. maculatum is known for being extremely poisonous. Its tissues contain a number of different alkaloids. In flower buds, the major alkaloid found is γ-coniceine. This molecule is transformed into coniine later during the fruit development. [30] The alkaloids are volatile; as such, researchers assume that these alkaloids play an important role in attracting pollinators such as butterflies and bees. [31]
Conium contains the piperidine alkaloids coniine, N-methylconiine, conhydrine, pseudoconhydrine and gamma-coniceine (or g-coniceïne), which is the precursor of the other hemlock alkaloids. [19] [32] [33] [34]
Coniine has pharmacological properties and a chemical structure similar to nicotine. [19] [35] Coniine acts directly on the central nervous system through inhibitory action on nicotinic acetylcholine receptors. Coniine can be dangerous to humans and livestock. [33] With its high potency, the ingestion of seemingly small doses can easily result in respiratory collapse and death. [36]
The alkaloid content in C. maculatum also affects the thermoregulatory centre by a phenomenon called peripheral vasoconstriction, resulting in hypothermia in calves. [37] In addition, the alkaloid content was also found to stimulate the sympathetic ganglia and reduce the influence of the parasympathetic ganglia in rats and rabbits, causing an increased heart rate. [38]
Coniine also has significant toxic effects on the kidneys. The presence of rhabdomyolysis and acute tubular necrosis has been shown in patients who died from hemlock poisoning. A fraction of these patients were also found to have acute kidney injury. [39] Coniine is toxic for the kidneys because it leads to the constriction of the urinary bladder sphincter and eventually the accumulation of urine. [40]
A short time after ingestion, the alkaloids induce potentially fatal neuromuscular dysfunction due to failure of the respiratory muscles. Acute toxicity, if not lethal, may resolve in spontaneous recovery, provided further exposure is avoided. Death can be prevented by artificial ventilation until the effects have worn off 48–72 hours later. [19] For an adult, the ingestion of more than 100 mg (0.1 gram) of coniine (about six to eight fresh leaves, or a smaller dose of the seeds or root) may be fatal. Narcotic-like effects can be observed as soon as 30 minutes after ingestion of green leaf matter of the plant, with victims falling asleep and unconsciousness gradually deepening until death a few hours later. [41]
The onset of symptoms is similar to that caused by curare, with an ascending muscular paralysis leading to paralysis of the respiratory muscles, causing death from oxygen deprivation. [42]
It has been observed that poisoned animals return to feed on the plant after initial poisoning. Chronic toxicity affects only pregnant animals when they are poisoned at low levels by C. maculatum during the fetus' organ-formation period; in such cases the offspring is born with malformations, mainly palatoschisis and multiple congenital contractures (arthrogryposis). The damage to the fetus due to chronic toxicity is irreversible. Though arthrogryposis may be surgically corrected in some cases, most of the malformed animals die. Such losses may be underestimated, at least in some regions, because of the difficulty in associating malformations with the much earlier maternal poisoning.
Since no specific antidote is available, prevention is the only way to deal with the production losses caused by the plant. Control with herbicides and grazing with less-susceptible animals (such as sheep) have been suggested. It is a common myth that C. maculatum alkaloids can enter the human food chain via milk and fowl, and scientific studies have disproven these claims. [43]
In ancient Greece, hemlock was used to poison condemned prisoners. Conium maculatum is the plant that killed Theramenes, Socrates, Polemarchus, and Phocion. [44] Socrates, the most famous victim of hemlock poisoning, was accused of impiety and corrupting the minds of the young men of Athens in 399 BC, and his trial gave down his death sentence. He decided to take a potent infusion of hemlock.
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen or sulfur. More rarely still, they may contain elements such as phosphorus, chlorine, and bromine.
Daucus carota, whose common names include wild carrot, European wild carrot, bird's nest, bishop's lace, and Queen Anne's lace, is a flowering plant in the family Apiaceae. It is native to temperate regions of the Old World and was naturalized in the New World.
Conium is a genus of flowering plants in the family Apiaceae. As of December 2020, Plants of the World Online accepts six species.
Coniine is a poisonous chemical compound, an alkaloid present in and isolable from poison hemlock (Conium maculatum), where its presence has been a source of significant economic, medical, and historico-cultural interest; coniine is also produced by the yellow pitcher plant (Sarracenia flava), and fool's parsley (Aethusa cynapium). Its ingestion and extended exposure are toxic to humans and all classes of livestock; its mechanism of poisoning involves disruption of the central nervous system, with death caused by respiratory paralysis. The biosynthesis of coniine contains as its penultimate step the non-enzymatic cyclisation of 5-oxooctylamine to γ-coniceine, a Schiff base differing from coniine only by its carbon-nitrogen double bond in the ring. This pathway results in natural coniine that is a mixture—a racemate—composed of two enantiomers, the stereoisomers (S)-(+)-coniine and (R)-(−)-coniine, depending on the direction taken by the chain that branches from the ring. Both enantiomers are toxic, with the (R)-enantiomer being the more biologically active and toxic of the two in general. Coniine holds a place in organic chemistry history as being the first of the important class of alkaloids to be synthesized, by Albert Ladenburg in 1886, and it has been synthesized in the laboratory in a number of unique ways through to modern times.
Cicuta virosa, the cowbane or northern water hemlock, is a poisonous species of Cicuta, native to northern and central Europe, northern Asia and northwestern North America.
Cicutoxin is a naturally-occurring poisonous chemical compound produced by several plants from the family Apiaceae including water hemlock (Cicuta species) and water dropwort (Oenanthe crocata). The compound contains polyene, polyyne, and alcohol functional groups and is a structural isomer of oenanthotoxin, also found in water dropwort. Both of these belong to the C17-polyacetylenes chemical class.
Cicuta, commonly known as water hemlock, is a genus of four species of highly poisonous plants in the family Apiaceae. They are perennial herbaceous plants which grow up to 2.5 meters (8 ft) tall, having distinctive small green or white flowers arranged in an umbrella shape (umbel). Plants in this genus may also be referred to as cowbane or poison parsnip. Cicuta is native to temperate regions of the Northern Hemisphere, mainly North America and Europe, typically growing in wet meadows, along streambanks and other wet and marshy areas. These plants bear a close resemblance to other members in the family Apiaceae and may be confused with a number of edible or poisonous plants. The common name hemlock may also be confused with poison hemlock, or with the Hemlock tree.
Taxus cuspidata, the Japanese yew or spreading yew, is a member of the genus Taxus, native to Japan, Korea, northeast China and the extreme southeast of Russia.
Cicuta maculata is a highly poisonous species of flowering plant in the carrot family known by several common names, including spotted water hemlock, spotted parsley, spotted cowbane, and the suicide root by the Iroquois. It is native to nearly all of North America, from northern Canada to southern Mexico.
Ligusticum porteri, also known as oshá, wild parsnip, Porter’s Lovage or wild celery, is a perennial herb found in parts of the Rocky Mountains and northern New Mexico, especially in the southwestern United States.
Aconitum napellus, monkshood, aconite, Venus' chariot or wolfsbane, is a species of highly toxic flowering plants in the genus Aconitum of the family Ranunculaceae, native and endemic to western and central Europe. It is an herbaceous perennial plant growing to 1 m tall, with hairless stems and leaves. The leaves are rounded, 5–10 cm (2.0–3.9 in) diameter, palmately divided into five to seven deeply lobed segments. The flowers are dark purple to bluish-purple, narrow oblong helmet-shaped, 1–2 cm (0.39–0.79 in) tall. Plants native to Asia and North America formerly listed as A. napellus are now regarded as separate species. The plant is extremely poisonous in both ingestion and body contact.
Oenanthotoxin is a toxin extracted from hemlock water-dropwort and other plants of the genus Oenanthe. It is a central nervous system poison, and acts as a noncompetitive antagonist of the neurotransmitter gamma-aminobutyric acid. A case has been made for the presence of this toxin in local Oenanthe species playing a causative role in euthanasia in ancient Sardinia. It was crystallized in 1949 by Clarke and co-workers. It is structurally closely related to the toxins cicutoxin and carotatoxin. Oenanthotoxin is a C17 polyacetylene isomer of cicutoxin.
Sium suave, the water parsnip or hemlock waterparsnip, is a perennial wildflower in the family Apiaceae. It is native to many areas of both Asia and North America. The common name water parsnip is due to its similarity to parsnip and its wetland habitat. The alternate common name hemlock waterparsnip is due to its similarity to the highly poisonous spotted water hemlock.
Coturnism is an illness featuring muscle tenderness and rhabdomyolysis after consuming quail that have fed on poisonous plants.
The hemlock moth, also known as the defoliating hemlock moth or poison hemlock moth, is a nocturnal moth species of the family Depressariidae. Of Palaearctic origin, it was first found in North America in 1973 when it was accidentally introduced. The moth is now widespread throughout the northern half of the United States, southern Canada, northern Europe, and, more recently, New Zealand and Australia. The larval form grows to around 10 mm, while the adults wingspan is between 17 mm and 19 mm.
Lupinus formosus, the summer lupine or western lupine, is a species of flowering plant in the legume family, Fabaceae. It is native to California and Oregon in the United States.
Conhydrine is a poisonous alkaloid found in poison hemlock in small quantities.
Oenanthe crocata, hemlock water-dropwort is a flowering plant in the carrot family, native to Europe, North Africa and western Asia. It grows in damp grassland and wet woodland, often along river and stream banks. All parts of the plant are extremely toxic and it has been known to cause human and livestock poisoning.
Conium alkaloids are natural products of the piperidine alkaloid type.