Botanical sexism is a term that describes the preferential planting of cloned male plants in urban areas because they do not produce fruits and flowers that litter the landscape. However, because males produce pollen, areas with only male plants can have high pollen in the air and, therefore, be inhospitable to people with pollen allergies.
According to horticulturist Tom Ogren, who coined the term, pollen allergies have been amplified due to the planting in urban areas of male clones, which increases the amount of pollen in the air. The planting of more female plants would decrease the overall amount of pollen since they do not produce pollen and remove pollen from the air for pollination. [1] The theory has existed since at least the 2000s. [2] [3] Biological sexism is used in the Ogren Plant Allergy Scale (OPALS), which has been adopted by the United States Department of Agriculture. [4] Botanical sexism has found some scientific acceptance as a reason for increased allergies and asthma; [5] [6] however, other scientists have also been critical of it, stating that it only applies to certain trees and is not as widespread as Ogren alleges. [2] [7]
The dioecious species affected by botanical sexism include willows, poplars, aspens, ashes, silver maples, pistache, mulberry, pepper tree and other woody plants such as junipers, yew pines, fern pines, wax myrtles, alpine currants, plum yews, and yews. [1]
The claims made about botanical sexism have been contested. Rita Sousa-Silva, an assistant professor of ecology at the University of Leiden, has said that the OPALS rating system has "no scientific background". [8] Some have pointed out that the majority of tree species (~75% globally) are cosexual, meaning they produce flowers with both male and female parts. As a result, a human sexual binary does not apply to most trees, with only 5% globally being dioecious, though this does not preclude the possibility that urban trees could be largely male. [9] William Elmendorf, a professor of urban forestry management at Penn State University, has said that terms like "fruitless" or "podless" were previously used more commonly to refer to dioecious trees selected for low fruit production, such as ginkgos. [10] It has been noted that there is limited data to confirm or deny the claim that male trees are more prevalent than female trees in the urban landscape. [11] The idea that additional female trees would significantly reduce pollen has also been challenged with some instead pointing to planting fewer wind-pollinated species. [12]
Kiwifruit or Chinese gooseberry is the edible berry of several species of woody vines in the genus Actinidia. The most common cultivar group of kiwifruit is oval, about the size of a large hen's egg: 5–8 centimetres in length and 4.5–5.5 cm in diameter. It has a thin, fuzzy, fibrous, tart but edible light brown skin and light green or golden flesh with rows of tiny, black, edible seeds. The fruit has a soft texture with a sweet and unique flavour.
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains, which produce male gametes. Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of gymnosperms. If pollen lands on a compatible pistil or female cone, it germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail. The study of pollen is called palynology and is highly useful in paleoecology, paleontology, archaeology, and forensics. Pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to the stigma of another in cross-pollination. In a case of self-pollination, this process takes place from the anther of a flower to the stigma of the same flower.
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta, also known as Coniferophyta or Coniferae. The division contains a single extant class, Pinopsida. All extant conifers are perennial woody plants with secondary growth. The great majority are trees, though a few are shrubs. Examples include cedars, Douglas-firs, cypresses, firs, junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and yews. As of 2002, Pinophyta contained seven families, 60 to 65 genera, and more than 600 living species.
Morus, a genus of flowering plants in the family Moraceae, consists of diverse species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions. Generally, the genus has 64 subordinate taxa, three of which are well-known and are ostensibly named for the fruit color of the best-known cultivar: white, red, and black mulberry, with numerous cultivars and some taxa currently unchecked and awaiting taxonomic scrutiny. M. alba is native to South Asia, but is widely distributed across Europe, Southern Africa, South America, and North America. M. alba is also the species most preferred by the silkworm, and is regarded as an invasive species in Brazil and the United States.
Junipers are coniferous trees and shrubs in the genus Juniperus of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere, from the Arctic, south to tropical Africa, throughout parts of western, central and southern Asia, east to eastern Tibet in the Old World, and in the mountains of Central America. The highest-known juniper forest occurs at an altitude of 4,900 metres (16,100 ft) in southeastern Tibet and the northern Himalayas, creating one of the highest tree lines on earth.
Strelitzia is a genus of five species of perennial plants, native to South Africa. It belongs to the plant family Strelitziaceae. A common name of the genus is bird of paradise flower/plant, because of a resemblance of its flowers to birds-of-paradise. In South Africa, it is commonly known as a crane flower.
Taxus is a genus of coniferous trees or shrubs known as yews in the family Taxaceae. Yews occur around the globe in temperate zones of the northern hemisphere, northernmost in Norway and southernmost in the South Celebes. Some populations exist in tropical highlands.
A pollenizer, sometimes pollinizer is a plant that provides pollen.
Cupressaceae is a conifer family, the cypress, with worldwide distribution. The family includes 27–30 genera, which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecious trees and shrubs up to 116 m (381 ft) tall. The bark of mature trees is commonly orange- to red-brown and of stringy texture, often flaking or peeling in vertical strips, but smooth, scaly or hard and square-cracked in some species.
Podocarpus is a genus of conifers, the most numerous and widely distributed of the podocarp family, the Podocarpaceae. The name comes from Greek πούς + καρπός. Podocarpus species are evergreen shrubs or trees, usually from 1 to 25 m tall, known to reach 40 m (130 ft) at times. The cones have two to five fused cone scales, which form a fleshy, berry-like, brightly coloured receptacle at maturity. The fleshy cones attract birds, which then eat the cones and disperse the seeds in their droppings. About 97 to 107 species are placed in the genus depending on the circumscription of the species.
Plant reproductive morphology is the study of the physical form and structure of those parts of plants directly or indirectly concerned with sexual reproduction.
Dioecy is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly or indirectly. Dioecious reproduction is biparental reproduction. Dioecy has costs, since only the female part of the population directly produces offspring. It is one method for excluding self-fertilization and promoting allogamy (outcrossing), and thus tends to reduce the expression of recessive deleterious mutations present in a population. Plants have several other methods of preventing self-fertilization including, for example, dichogamy, herkogamy, and self-incompatibility.
Strelitzia reginae, commonly known as the crane flower, bird of paradise, or isigude in Nguni, is a species of flowering plant native to the Cape Provinces and KwaZulu-Natal in South Africa. An evergreen perennial, it is widely cultivated for its dramatic flowers. In temperate areas it is a popular houseplant.
Taxus baccata is a species of evergreen tree in the family Taxaceae, native to Western Europe, Central Europe and Southern Europe, as well as Northwest Africa, northern Iran, and Southwest Asia. It is the tree originally known as yew, though with other related trees becoming known, it may be referred to as common yew, European yew, or in North America English yew. It is a woodland tree in its native range, and it's also grown as an ornamental tree, hedge or topiary. Most parts of the plant are poisonous, with toxins that can be absorbed through inhalation, ingestion and through the skin; consumption of even a small amount of the foliage can result in death.
The paper mulberry is a species of flowering plant in the family Moraceae. It is native to Asia, where its range includes mainland China, Taiwan, Japan, Korea, Southeast Asia, Myanmar, and India. It is widely cultivated elsewhere and it grows as an introduced species in New Zealand, parts of Europe, the United States, and Africa. Other common names include tapa cloth tree.
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.
Taxus wallichiana, the Himalayan yew, is a species of yew, native to the Himalaya and parts of south-east Asia. The species has a variety of uses in traditional medicine. It is currently classified as endangered by the IUCN.
Juniperus pinchotii, commonly known as Pinchot juniper or redberry juniper, is a species of juniper native to south-western North America, in Mexico: Nuevo León and Coahuila, and in the United States: south-eastern New Mexico, central Texas, and western Oklahoma.
Ficus hispida, also known as the opposite leaf Fig, is a small tree in the family Moraceae, with a distribution ranging from India and southern China southwards to northern Australia. It is morphologically gynodioecious, but functionally dioecious. Male trees are hermaphrodites with both staminate flowers that produce pollen and pistillate flowers that produce almost no seeds but can form galls containing pollinator wasp larvae. Female trees have pistillate flowers that do produce seeds but are inhospitable to pollinator wasp larvae.
The Ogren Plant Allergy Scale (OPALS) is an allergy rating system for plants that measures the potential of a plant to cause allergic reactions in humans.
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