Ragweed | |
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Ambrosia psilostachya | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Asterales |
Family: | Asteraceae |
Subfamily: | Asteroideae |
Tribe: | Heliantheae |
Subtribe: | Ambrosiinae |
Genus: | Ambrosia L. |
Synonyms [1] | |
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Ragweeds are flowering plants in the genus Ambrosia in the aster family, Asteraceae. They are distributed in the tropical and subtropical regions of the Americas, especially North America, [2] where the origin and center of diversity of the genus are in the southwestern United States and northwestern Mexico. [3] Several species have been introduced to the Old World and some have naturalized and have become invasive species. [2] In Europe, this spread is expected to continue, due to ongoing climate change. [4]
The name "ragweed" is derived from "ragged" + "weed," coming from the ragged appearance of the plant's leaves. [5] Other common names include bursages [6] and burrobrushes. [7] The genus name is from the Greek ambrosia , meaning "food or drink of immortality". [2]
Ragweed pollen is notorious for causing allergic reactions in humans, specifically allergic rhinitis. Up to half of all cases of pollen-related allergic rhinitis in North America are caused by ragweeds. [8]
The most widespread species of the genus in North America is Ambrosia artemisiifolia .
Ragweeds are annual and perennial herbs and shrubs. Species may grow just a few centimeters tall or exceed four meters in height. The stems are erect, decumbent or prostrate, and many grow from rhizomes. The leaves may be arranged alternately, oppositely, or both. The leaf blades come in many shapes, sometimes divided pinnately or palmately into lobes. The edges are smooth or toothed. Some are hairy, and most are glandular. [2]
Ragweeds are monoecious, most producing inflorescences that contain both staminate and pistillate flowers. Inflorescences are often in the form of a spike or raceme made up mostly of staminate flowers with some pistillate clusters around the base. Staminate flower heads have stamens surrounded by whitish or purplish florets. Pistillate flower heads have fruit-yielding ovules surrounded by many phyllaries and fewer, smaller florets. [2] The pistillate flowers are wind pollinated, [9] [10] and the fruits develop. They are burs, sometimes adorned with knobs, wings, or spines. [2]
Many Ambrosia species occur in desert and semi-desert areas, and many are ruderal species that grow in disturbed habitat types. [3]
Ragweed pollen is a common allergen. A single plant may produce about a billion grains of pollen per season, [11] [12] and the pollen is transported on the wind. It causes about half of all cases of pollen-associated allergic rhinitis in North America, where ragweeds are most abundant and diverse. [8] Common culprits are common ragweed (A. artemisiifolia) and great ragweed (A. trifida). [13]
Concentration of ragweed pollen—in the absence of significant rainfall, which removes pollen from the air- is the lowest in the early morning hours (6:00 AM), when emissions starts. Pollen concentration peaks at midday. [14] Ragweed pollen can remain airborne for days and travel great distances, and can even be carried 300–400 miles (500–600 km) out to sea. [12] Ragweeds native to the Americas have been introduced to Europe starting in the nineteenth century and especially during World War I, and have spread rapidly since the 1950s. [15] Eastern Europe, particularly Hungary, has been badly affected by ragweed since the early 1990s, when the dismantling of Communist collective agriculture led to large-scale abandonment of agricultural land, and new building projects also resulted in disturbed, un-landscaped areas. [16]
The major allergenic compound in the pollen has been identified as Amb a 1, a 38 kDa nonglycosylated protein composed of two subunits. It also contains other allergenic components, such as profilin and calcium-binding proteins. [17]
Ragweed allergy sufferers may show signs of oral allergy syndrome, a food allergy classified by a cluster of allergic reactions in the mouth in response to the consumption of certain fruits, vegetables, and nuts. [18] Foods commonly involved include beans, celery, cumin, hazelnuts, kiwifruit, parsley, potatoes, bananas, melons, cucumbers, and zucchini. Because cooking usually denatures the proteins that cause the reaction, the foods are more allergenic when eaten raw; exceptions are celery and nuts, which may not be safe even when cooked. Signs of reaction can include itching, burning, and swelling of the mouth and throat, runny eyes and nose, hives, and, less commonly, vomiting, diarrhea, asthma, and anaphylaxis. These symptoms are due to the abnormal increase of IgE antibodies which attach to a type of immune cell called mast cells. When the ragweed antigen then attaches to these antibodies the mast cells release histamine and other symptom-evoking chemicals. [19]
Merck & Co, under license from allergy immunotherapy (AIT) company ALK, has launched a ragweed allergy immunotherapy treatment in sublingual tablet form in the US and Canada.[ citation needed ]
As of 2006, research into allergy immunotherapy treatment involved administering doses of the allergen to accustom the body to induce specific long-term tolerance. [20]
Where herbicides cannot be used, mowing may be repeated about every three weeks, as it grows back rapidly. In the past, ragweed was usually cut down, left to dry, and then burned. [21] This method is used less often now, because of the pollution caused by smoke. Manually uprooting ragweed is generally ineffective, and skin contact can cause allergic reaction. If uprooting is the method of choice, it should be performed before flowering. There is evidence that mechanical and chemical control methods are actually no more effective in the long run than leaving the weed in place. [21]
Fungal rusts and the leaf-eating beetle Ophraella communa have been proposed as agents of biological pest control of ragweeds, but the latter may also attack sunflowers, and applications for permits and funding to test these controls have been unsuccessful. [22] The beetle has, however, appeared in Europe, either on its own or as an uncontrolled introduction, and it has started making a dent into Ambrosia populations there. [23] [24] [25] [26]
There are about 50 species in genus Ambrosia. Species include: [27]
An allergen is an otherwise harmless substance that triggers an allergic reaction in sensitive individuals by stimulating an immune response.
Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, itchy, and watery eyes, and swelling around the eyes. The fluid from the nose is usually clear. Symptom onset is often within minutes following allergen exposure, and can affect sleep and the ability to work or study. Some people may develop symptoms only during specific times of the year, often as a result of pollen exposure. Many people with allergic rhinitis also have asthma, allergic conjunctivitis, or atopic dermatitis.
Allergen immunotherapy, also known as desensitization or hypo-sensitization, is a medical treatment for environmental allergies and asthma. Immunotherapy involves exposing people to larger and larger amounts of allergens in an attempt to change the immune system's response.
Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including grasses, sedges, and rushes. Other common anemophilous plants are oaks, pecans, pistachios, sweet chestnuts, alders and members of the family Juglandaceae. Approximately 12% of plants across the globe are pollinated by anemophily, including cereal crops like rice and corn and other prominent crop plants like wheat, rye, barley, and oats. In addition, many pines, spruces, and firs are wind-pollinated.
Ambrosia artemisiifolia, with the common names common ragweed, annual ragweed, and low ragweed, is a species of the genus Ambrosia native to regions of the Americas.
Oral allergy syndrome (OAS) or pollen-food allergy syndrome (PFAS) is a type of allergy classified by a cluster of allergic reactions in the mouth and throat in response to eating certain fruits, nuts, and vegetables. It typically develops in adults with hay fever. It is not usually serious.
Ambrosia dumosa, the burro-weed or white bursage, a North American species of plants in the family Asteraceae. It is a common constituent of the creosote-bush scrub community throughout the Mojave desert of California, Nevada, and Utah and the Sonoran Desert of Arizona and northwestern Mexico.
Ambrosia trifida, the giant ragweed, is a species of flowering plant in the family Asteraceae. It is native to North America, where it is widespread in Canada, the United States, and northern Mexico.
Ambrosia ambrosioides, also known as canyon ragweed or chicura, is a ragweed found in the deserts of northern Mexico, Arizona, and California.
Pectate lyase is an enzyme involved in the maceration and soft rotting of plant tissue. Pectate lyase is responsible for the eliminative cleavage of pectate, yielding oligosaccharides with 4-deoxy-α-D-mann-4-enuronosyl groups at their non-reducing ends. The protein is maximally expressed late in pollen development. It has been suggested that the pollen expression of pectate lyase genes might relate to a requirement for pectin degradation during pollen tube growth.
Ambrosia acanthicarpa is a North American species of bristly annual plants in the family Asteraceae. Members of the genus Ambrosia are called ragweeds. The species has common names including flatspine bur ragweed, Hooker's bur-ragweed, annual burrweed, annual bur-sage, and western sand-bur. The plant is common across much of the western United States and in the Prairie Provinces of Canada.
Ambrosia psilostachya is a species of ragweed known by the common names Cuman ragweed and perennial ragweed, and western ragweed.
Ambrosia chenopodiifolia is a species of ragweed known by the common names San Diego bursage and San Diego bur ragweed. It is native to the Mexican states of Baja California and Baja California Sur, as well as to Orange and San Diego Counties it int US State of California. It is a member of the coastal sage scrub plant community.
Ambrosia confertiflora is a North American species of ragweed known by the common name weakleaf bur ragweed.
Ambrosia eriocentra is a North American species of ragweed known by the common names woolly bursage and woollyfruit burr ragweed.
Ambrosia ilicifolia is a species of ragweed known by the common names hollyleaf burr ragweed and hollyleaf bursage.
Ambrosia tomentosa, the skeletonleaf bur ragweed, silverleaf povertyweed, or skeleton-leaf bursage, is a North American species of perennial plants in the family Asteraceae.
Ambrosia deltoidea is a North American species of flowering plant in the family Asteraceae known by the common names triangle bur ragweed, triangle bursage, and triangleleaf bursage.
Ophraella communa, common name ragweed leaf beetle, is a species of beetles belonging to the family Chrysomelidae.
Ambrosia cordifolia, called the Tucson bur ragweed, is a North American species of plant in the family Asteraceae. It is native to northern Mexico and the State of Arizona in the United States.