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102-503: The avocado , alligator pear or avocado pear ( Persea americana ) is an evergreen tree in the laurel family ( Lauraceae ). It is native to the Americas and was first domesticated in Mesoamerica more than 5,000 years ago. It was prized for its large and unusually oily fruit . The tree likely originated in the highlands bridging south-central Mexico and Guatemala . Avocado trees have

204-635: A type section , Global Boundary Stratotype Section and Point (GSSP), for the upper Pleistocene/Holocene boundary ( i.e. the upper boundary). The proposed section is the North Greenland Ice Core Project ice core 75° 06' N 42° 18' W. The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone , isotopic stage 103. Above this point there are notable extinctions of

306-447: A "cocktail avocado", which does not contain a pit, is available on a limited basis. They are five to eight centimetres long; the whole fruit may be eaten, including the skin. It is produced from an unpollinated blossom in which the seed does not develop. Seedless avocados regularly appear on trees. Known in the avocado industry as "cukes", they are usually discarded commercially due to their small size. In 2020, world production of avocados

408-507: A 6% increase over the previous year, and that 2 million tonnes would be exported. The Mexican state of Michoacán is the world leader in avocado production, accounting for 80% of all Mexican output. Most Mexican growers produce the Hass variety due to its longer shelf life for shipping and high demand among consumers. Seventy-six percent of Mexico's avocado exports go to the United States, with

510-585: A change from low-amplitude glacial cycles with a dominant periodicity of 41,000 years to asymmetric high-amplitude cycles dominated by a periodicity of 100,000 years. However, a 2020 study concluded that ice age terminations might have been influenced by obliquity since the Mid-Pleistocene Transition, which caused stronger summers in the Northern Hemisphere . Glaciation in the Pleistocene

612-497: A cold or dry/wet season. Evergreen trees also lose leaves, but each tree loses its leaves gradually and not all at once. Most tropical rainforest plants are considered to be evergreens, replacing their leaves gradually throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous. Most warm temperate climate plants are also evergreen. In cool temperate climates, fewer plants are evergreen. In such climates, there

714-409: A decorative houseplant . The pit germinates in normal soil conditions or partially submerged in a small glass (or container) of water. In the latter method, the pit sprouts in four to six weeks, at which time it is planted in standard houseplant potting soil. The plant normally grows large enough to be prunable; it does not bear fruit unless it has ample sunlight. Home gardeners can graft a branch from

816-574: A deviation from today's annual mean temperature, taken as zero. This sort of graph is based on another isotope ratio versus time. Ratios are converted to a percentage difference from the ratio found in standard mean ocean water (SMOW). The graph in either form appears as a waveform with overtones . One half of a period is a Marine isotopic stage (MIS). It indicates a glacial (below zero) or an interglacial (above zero). Overtones are stadials or interstadials. According to this evidence, Earth experienced 102 MIS stages beginning at about 2.588 Ma BP in

918-421: A few regions had been studied and the names were relatively few. Today the geologists of different nations are taking more of an interest in Pleistocene glaciology. As a consequence, the number of names is expanding rapidly and will continue to expand. Many of the advances and stadials remain unnamed. Also, the terrestrial evidence for some of them has been erased or obscured by larger ones, but evidence remains from

1020-599: A frequent claim is that testicle was the word's original meaning. This is not the case, as the original meaning can be reconstructed as "avocado" – rather the word seems to have been used in Nahuatl as a euphemism for "testicle". The modern English name comes from a rendering of the Spanish aguacate as avogato . The earliest known written use in English is attested from 1697 as avogato pear , later avocado pear (due to its shape),

1122-492: A fruit-bearing plant to speed maturity, which typically takes four to six years to bear fruit. Avocado trees are vulnerable to bacterial, viral , fungal , and nutritional diseases (excesses and deficiencies of key minerals). Disease can affect all parts of the plant, causing spotting, rotting, cankers, pitting, and discoloration. The pyriform scale insect ( Protopulvinaria pyriformis ) is known from Australia, South Africa, Israel, Italy, France, Spain, Cuba, Florida, and Peru. It

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1224-731: A higher soil acidity and lower soil nitrogen content. This is the case with Mediterranean evergreen seedlings, which have unique C and N storages that allow stored resources to determine fast growth within the species, limiting competition and bolstering survival. These conditions favor the growth of more evergreens and make it more difficult for deciduous plants to persist. In addition, the shelter provided by existing evergreen plants can make it easier for younger evergreen plants to survive cold and/or drought. Evergreen plants can have decorative as well as functional uses. In months where most other plants are dormant, evergreens with their sturdy structure, and vibrant foliage are popular choices to beautify

1326-510: A landscape. Additionally, evergreens can serve as a windbreak , stopping heat loss from buildings during cold months when placed on the northwest side of a structure. Pleistocene The Pleistocene ( / ˈ p l aɪ s t ə ˌ s iː n , - s t oʊ -/ PLY -stə-seen, -⁠stoh- ; referred to colloquially as the Ice Age ) is the geological epoch that lasted from c.  2.58 million to 11,700 years ago, spanning

1428-420: A larger volume of parenchyma and air spaces per unit leaf area. They have larger leaf biomass per unit leaf area, and hence a lower specific leaf area . Construction costs do not differ between the groups. Evergreens have generally a larger fraction of total plant biomass present as leaves (LMF), but they often have a lower rate of photosynthesis. Deciduous trees shed their leaves usually as an adaptation to

1530-509: A native growth range from Mexico to Costa Rica . Its fruit, sometimes also referred to as an alligator pear or avocado pear , is botanically a large berry containing a single large seed. Sequencing of its genome showed that the evolution of avocados was shaped by polyploidy events and that commercial varieties have a hybrid origin. Avocado trees are partly self-pollinating , and are often propagated through grafting to maintain consistent fruit output. Avocados are presently cultivated in

1632-413: A problem, with heavy crops in one year being followed by poor yields the next. Like the banana, the avocado is a climacteric fruit, which matures on the tree, but ripens off the tree. Avocados used in commerce are picked hard and green and kept in coolers at 3.3 to 5.6 °C (37.9 to 42.1 °F) until they reach their final destination. Avocados must be mature to ripen properly. Avocados that fall off

1734-580: A staple fruit in Chile with 30% of production destined for the domestic market. No import tariffs are imposed on Chilean avocados by China, the United States, or the European Union due to free trade agreements. Other avocado cultivars include 'Spinks' . Historically attested varieties (which may or may not survive among horticulturists ) include the 'Challenge', 'Dickinson', 'Kist', 'Queen', 'Rey', 'Royal', 'Sharpless', and 'Taft'. A stoneless avocado, marketed as

1836-568: A team of Russian scientists in collaboration with Princeton University announced that they had brought two female nematodes frozen in permafrost , from around 42,000 years ago, back to life. The two nematodes, at the time, were the oldest confirmed living animals on the planet. The evolution of anatomically modern humans took place during the Pleistocene. At the beginning of the Pleistocene Paranthropus species were still present, as well as early human ancestors, but during

1938-519: A term sometimes corrupted to alligator pear . In Central American, Caribbean Spanish-speaking countries, and Spain it is known by the Mexican Spanish name aguacate , while South American Spanish-speaking countries Argentina, Chile, Perú and Uruguay use a Quechua -derived word, palta . In Portuguese, it is abacate . The Nahuatl āhuacatl can be compounded with other words, as in ahuacamolli , meaning avocado soup or sauce, from which

2040-578: A thinner exocarp because of selective breeding by humans. The species was scientifically named by the British botanist Philip Miller in 1768. The genus Persea to which the avocado belongs is considered to have a North American origin, with Persea suggested to have diversified in Central America during the Pleistocene epoch. The modern avocado is thought to have speciated from other Persea during

2142-513: A wide range through human agency before the arrival of the Europeans. The three separate landraces were most likely to have already intermingled in pre-Columbian America and were described in the Florentine Codex . As a result of artificial selection , the fruit and correspondingly the seeds of cultivated avocados became considerably larger relative to their earlier wild forebears millennia before

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2244-613: Is a climacteric , single-seeded berry , due to the imperceptible endocarp covering the seed, rather than a drupe . The pear-shaped fruit is usually 7–20 cm (3–8 in) long, weighs between 100 and 1,000 g ( 3 + 1 ⁄ 2 and 35 + 1 ⁄ 2  oz), and has a large central seed , 5–6.4 cm (2– 2 + 1 ⁄ 2  in) long. Early wild avocados prior to domestication had much smaller seeds around 2.1–2.2 centimetres (0.83–0.87 in) in diameter, likely corresponding to smaller fruit size. The species produces various cultivars with larger, fleshier fruits with

2346-438: Is a predominance of conifers because few evergreen broadleaf plants can tolerate severe cold below about −26 °C (−15 °F). In addition, evergreen foliage experiences significant leaf damage in these cold, dry climates. Root systems are the most vulnerable aspect of many plants. Even though roots are insulated by soil, which tends to be warmer than average air temperatures, soil temperatures that drop too low can kill

2448-765: Is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America , and several hundred in Eurasia . The mean annual temperature at the edge of the ice was −6 °C (21 °F); at the edge of the permafrost, 0 °C (32 °F). Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 metres (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 metres (300 ft) or more over

2550-602: Is limited to a small fraction of the vast genetic diversity in the species. Conservation of this genetic diversity has relied largely on field collection, as avocado seeds often do not survive storage in seed banks. This is problematic, as field preservation of living cultivars is expensive, and habitat loss threatens wild cultivars. More recently, an alternate method of conservation has been developed based on cryopreservation of avocado somatic embryos with reliable methods for somatic embryogenesis and reconstitution into living trees. The avocado tree can be grown domestically and used as

2652-634: Is located in Southern California . Avocado is the official fruit of the state of California. Fallbrook, California , claims, without official recognition, the title of "Avocado Capital of the World" (also claimed by the town of Uruapan in Mexico), and both it and Carpinteria, California , host annual avocado festivals. The California Avocado Commission and the California Avocado Society are

2754-454: Is no systematic correspondence between pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term "Riss pluvial" in Egyptian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been stratigraphically defined. The sum of transient factors acting at

2856-453: Is normally found on avocado, and in Peru it is said to be the worst insect pest of the fruit. Certain cultivars of avocado seem more susceptible to attack by the scale than others. Mexico is by far the world's largest avocado growing country, producing several times more than the second largest producer. In 2013, the total area dedicated to avocado production was 188,723 hectares (466,340 acres), and

2958-419: Is now an industry standard, was pioneered in the 1980s by farmer Gil Henry of Escondido, California , in response to footage from a hidden supermarket camera which showed shoppers repeatedly squeezing hard, unripe avocados, putting them "back in the bin", and moving on without making a purchase. In some cases, avocados can be left on the tree for several months, which is an advantage to commercial growers who seek

3060-537: Is poisonous to some birds, and the American Society for the Prevention of Cruelty to Animals (ASPCA) lists it as toxic to horses. Avocado leaves contain a toxic fatty acid derivative, persin , which in sufficient quantity can cause colic in horses and without veterinary treatment, death. The symptoms include gastrointestinal irritation, vomiting, diarrhea, respiratory distress, congestion, fluid accumulation around

3162-609: Is such a problem that the phrase blood guacamole has been adopted to describe the social effects in Mexico of the vast worldwide demand for its fruits. Avocados were introduced to California from Nicaragua in the early 1850s, when avocado trees imported from the Central American country were observed and reported growing near San Gabriel. The avocado has since become a successful cash crop . About 24,000 hectares (59,000 acres) – as of 2015, some 80% of United States avocado production –

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3264-432: Is unlikely to be identical to the parent cultivar in fruit quality. Prime quality varieties are therefore propagated by grafting to rootstocks that are propagated by seed (seedling rootstocks) or by layering (clonal rootstocks). After about a year of growing in a greenhouse, the young rootstocks are ready to be grafted. Terminal and lateral grafting is normally used. The scion cultivar grows for another 6–12 months before

3366-638: The Alpine ice sheet on the Alps . Scattered domes stretched across Siberia and the Arctic shelf. The northern seas were ice-covered. South of the ice sheets large lakes accumulated because outlets were blocked and the cooler air slowed evaporation. When the Laurentide Ice Sheet retreated, north-central North America was completely covered by Lake Agassiz . Over a hundred basins, now dry or nearly so, were overflowing in

3468-635: The Ruwenzori Range in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia and to the west in the Atlas Mountains . In the northern hemisphere, many glaciers fused into one. The Cordilleran Ice Sheet covered the North American northwest; the east was covered by the Laurentide . The Fenno-Scandian ice sheet rested on northern Europe , including much of Great Britain;

3570-595: The Tehuacan Valley in the state of Puebla , Mexico. There is evidence for three possible separate domestications of the avocado, resulting in the currently recognized Guatemalan ( quilaoacatl ), Mexican ( aoacatl ) and West Indian ( tlacacolaocatl ) landraces . The Guatemalan and Mexican and landraces originated in the highlands of those countries, while the West Indian landrace is a lowland variety that ranges from Guatemala, Costa Rica, Colombia, Ecuador to Peru, achieving

3672-799: The Water Footprint Network , it takes an average of approximately 70 litres (18 US gallons; 15 imperial gallons) of applied fresh ground or surface water, not including rainfall or natural moisture in the soil, to grow one avocado (283 L/kg [33.9 US gal/lb; 28.2 imp gal/lb]). However, the amount of water needed depends on where it is grown; for example, in the main avocado-growing region of Chile, about 320 L (85 US gal; 70 imp gal) of applied water are needed to grow one avocado (1,280 L/kg [153 US gal/lb; 128 imp gal/lb]). Increasing demand and production of avocados may cause water shortages in some avocado production areas, such as

3774-437: The calcareous nannofossils : Discoaster pentaradiatus and Discoaster surculus . The Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has, in the past, been used to mean the last ice age. Formerly, the boundary between the two epochs was drawn at the time when the foraminiferal species Hyalinea baltica first appeared in the marine section at La Castella, Calabria, Italy. However,

3876-628: The free trade agreement between the US, Canada and Mexico in July 2020 facilitating avocado shipments within the North American free trade zone . The Mexican domestic market was expanding during 2020. Mexican avocado exports are challenged by growth of production by Peru and the Dominican Republic to supply the US and European markets. During the COVID-19 pandemic , Mexican avocado farmers restricted harvesting as

3978-477: The last glacial period ended about 10,000 years ago. Over 11 major glacial events have been identified, as well as many minor glacial events. A major glacial event is a general glacial excursion, termed a "glacial." Glacials are separated by "interglacials". During a glacial, the glacier experiences minor advances and retreats. The minor excursion is a "stadial"; times between stadials are "interstadials". These events are defined differently in different regions of

4080-588: The woolly rhinoceros , various giraffids , such as the Sivatherium ; ground sloths , Irish elk , cave lions , cave bears , Gomphotheres , American lions , dire wolves , and short-faced bears , began late in the Pleistocene and continued into the Holocene. Neanderthals also became extinct during this period. At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice , migratory birds, and swifter animals like whitetail deer had replaced

4182-701: The "Tarantian"). In addition to these international subdivisions, various regional subdivisions are often used. In 2009 the International Union of Geological Sciences (IUGS) confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, and accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP . The start date has now been rounded down to 2.580 million years BP. The IUGS has yet to approve

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4284-485: The ' Hass ' cultivar can tolerate temperatures down to −1 °C. Several cold-hardy varieties are planted in the region of Gainesville, Florida , which survive temperatures as low as −6.5 °C (20 °F) with only minor leaf damage. The trees also need well-aerated soils, ideally more than 1 m deep. However, Guatemalan varieties such as "MacArthur", "Rincon", or "Nabal" can withstand temperatures down to −1.6 °C (29 °F) According to information published by

4386-472: The Columbian exchange. The earliest residents of northern coastal Peru were living in temporary camps in an ancient wetland and eating avocados, along with chilies, mollusks, sharks, birds, and sea lions. The oldest discovery of an avocado pit comes from Coxcatlan Cave , dating from around 9,000 to 10,000 years ago. Other caves in the Tehuacan Valley from around the same time period also show early evidence for

4488-558: The Early Pleistocene Gelasian . Early Pleistocene stages were shallow and frequent. The latest were the most intense and most widely spaced. By convention, stages are numbered from the Holocene, which is MIS1. Glacials receive an even number and interglacials receive an odd number. The first major glacial was MIS2-4 at about 85–11 ka BP. The largest glacials were 2, 6, 12, and 16. The warmest interglacials were 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under

4590-402: The Earth's most recent period of repeated glaciations . Before a change was finally confirmed in 2009 by the International Union of Geological Sciences , the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with

4692-409: The Earth's surface is cyclical: climate, ocean currents and other movements, wind currents, temperature, etc. The waveform response comes from the underlying cyclical motions of the planet, which eventually drag all the transients into harmony with them. The repeated glaciations of the Pleistocene were caused by the same factors. The Mid-Pleistocene Transition , approximately one million years ago, saw

4794-500: The Mexican state of Michoacán . Avocados may also cause environmental and socioeconomic impacts in major production areas, illegal deforestation , and water disputes . Water requirements for growing avocados are three times higher than for apples, and 18 times higher than for tomatoes. Commercial orchards produce an average of seven tonnes per hectare each year, with some orchards achieving 20 tonnes per hectare. Biennial bearing can be

4896-479: The North American west. Lake Bonneville , for example, stood where Great Salt Lake now does. In Eurasia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided . African lakes were fuller, apparently from decreased evaporation. Deserts, on the other hand, were drier and more extensive. Rainfall was lower because of the decreases in oceanic and other evaporation. It has been estimated that during

4998-490: The Pleistocene's overall climate could be characterised as a continuous El Niño with trade winds in the south Pacific weakening or heading east, warm air rising near Peru , warm water spreading from the west Pacific and the Indian Ocean to the east Pacific, and other El Niño markers. Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It

5100-479: The Pleistocene, estimated at around either 1.3 million or 430,000 years ago. A number of authors, including Connie Barlow in her 2001 book The Ghosts of Evolution , have speculated that the avocado is an " evolutionary anachronism " with megafaunal dispersal syndrome (a concept originally proposed in the 1980s by Paul S. Martin and Daniel H. Janzen ), arguing that the avocado likely coevolved dispersal of its large seed by now-extinct megafauna . Barlow proposed that

5202-782: The Pleistocene, the East Antarctic Ice Sheet thinned by at least 500 meters, and that thinning since the Last Glacial Maximum is less than 50 meters and probably started after ca 14 ka. During the 2.5 million years of the Pleistocene, numerous cold phases called glacials ( Quaternary ice age ), or significant advances of continental ice sheets, in Europe and North America, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of

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5304-411: The Pleistocene, the plates upon which they sit probably having moved no more than 100 km (62 mi) relative to each other since the beginning of the period. In glacial periods, the sea level would drop by up to 120 m (390 ft) lower than today during peak glaciation, exposing large areas of the present continental shelf as dry land. According to Mark Lynas (through collected data),

5406-620: The Pleistocene. The climate was strongly variable depending on the glacial cycle, with the sea levels being up to 120 metres (390 ft) lower than present at peak glaciation, allowing the connection of Asia and North America via Beringia and the covering of most of northern North America by the Laurentide Ice Sheet . Charles Lyell introduced the term "Pleistocene" in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today. This distinguished it from

5508-662: The Spanish word guacamole derives. In the United Kingdom the term avocado pear , applied when avocados first became commonly available in the 1960s, is sometimes used. Originating as a diminutive in Australian English , a clipped form, avo , has since become a common colloquialism in South Africa and the United Kingdom. It is known as "butter fruit" in parts of India and Hong Kong. Domestication, leading to genetically distinct cultivars, possibly originated in

5610-525: The Younger Dryas is the official start of the current Holocene Epoch . Although it is considered an epoch, the Holocene is not significantly different from previous interglacial intervals within the Pleistocene. In the ICS timescale, the Pleistocene is divided into four stages or ages , the Gelasian , Calabrian , Chibanian (previously the unofficial "Middle Pleistocene"), and Upper Pleistocene (unofficially

5712-687: The appearance of Homo sapiens about 300,000 years ago. Artifacts associated with modern human behavior are unambiguously attested starting 40,000–50,000 years ago. According to mitochondrial timing techniques, modern humans migrated from Africa after the Riss glaciation in the Middle Palaeolithic during the Eemian Stage , spreading all over the ice-free world during the late Pleistocene. A 2005 study posits that humans in this migration interbred with archaic human forms already outside of Africa by

5814-476: The area in which they reside. The excellent water economy within the evergreen species is due to high abundance when compared to deciduous species. Whereas deciduous trees lose nutrients whenever they lose their leaves. In warmer areas, species such as some pines and cypresses grow on poor soils and disturbed ground. In Rhododendron , a genus with many broadleaf evergreens, several species grow in mature forests but are usually found on highly acidic soil where

5916-515: The articles for those names. Both marine and continental faunas were essentially modern but with many more large land mammals such as Mammoths , Mastodons , Diprotodons , Smilodons , tigers , lions , Aurochs , short-faced bears , giant sloths , species within Gigantopithecus and others. Isolated landmasses such as Australia , Madagascar , New Zealand and islands in the Pacific saw

6018-594: The auspices of the Peruvian Avocado Commission, headquartered in Washington, D.C. Chile has produced avocados for over 100 years with production increasing dramatically in the early 1980s due to global demand. New York magazine reported in 2015 that "Large avocado growers are draining the country's groundwater and rivers faster than they can replenish themselves." 88% of total production and 99% of exported avocados from Chile are Hass avocados. Avocados are

6120-480: The avocado does not tolerate well), the trees tend to produce abundantly the next season. In addition, due to environmental circumstances during some years, seedless avocados may appear on the trees. Known in the avocado industry as "cukes", they are usually discarded commercially due to their small size. Avocados can be propagated by seed, taking roughly four to six years to bear fruit, although in some cases seedlings can take 10 years to come into bearing. The offspring

6222-675: The avocado in Europe is that of Martín Fernández de Enciso ( c.  1470  – 1528) in 1519 in his book, Suma De Geographia Que Trata De Todas Las Partidas Y Provincias Del Mundo , while describing the native settlement of Yaharo (present-day Dibulla , Colombia). The first detailed account that unequivocally describes the avocado was given by Gonzalo Fernández de Oviedo y Valdés in his work Sumario de la natural historia de las Indias in 1526, while holding administrative Spanish colonial duties in Santo Domingo and visiting Castilla de Oro . The first written record in English of

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6324-411: The axils of leaves. The tree flowers thousands of blossoms every year. Avocado blossoms sprout from racemes near the leaf axils; they are small and inconspicuous 5–10 mm ( 3 ⁄ 16 – 3 ⁄ 8  in) wide. They have no petals but instead two whorls of three pale-green or greenish-yellow downy perianth lobes, each blossom has 9 stamens with 2 basal orange nectar glands. The avocado fruit

6426-571: The chances of cross- pollination are reduced. That is the case for programs at the University of California, Riverside , as well as the Volcani Centre and the Instituto de Investigaciones Agropecuarias in Chile. The avocado is unusual in that the timing of the male and female flower phases differs among cultivars. The two flowering types are A and B. A-cultivar flowers open as female on the morning of

6528-476: The climate variation more extreme. The Late Pleistocene witnessed the spread of modern humans outside of Africa as well as the extinction of all other human species. Humans also spread to the Australian continent and the Americas for the first time, co-incident with the extinction of most large-bodied animals in these regions. The aridification and cooling trends of the preceding Neogene were continued in

6630-515: The dispersers included the gomphothere (elephant relative) Cuvieronius , as well as ground sloths , toxodontids , and glyptodonts . The concept of evolutionary anachronisms/megafaunal dispersal syndrome has been criticised by some authors, who note that many large fruit are readily dispersed by non-megafaunal animals, with it being noted that living agoutis disperse avocado seeds, with spectacled bears have also having been observed eating domestic avocados. The earliest known written account of

6732-529: The end of the last glacial period and also with the end of the Paleolithic age used in archaeology . The name is a combination of Ancient Greek πλεῖστος ( pleîstos ) 'most' and καινός ( kainós ; Latinized as cænus ) 'new'. At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama , causing a faunal interchange between

6834-606: The entire surface of the Earth. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions. The effects of glaciation were global. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Zealand and Tasmania . The current decaying glaciers of Mount Kenya , Mount Kilimanjaro , and

6936-546: The evergreen nature of the plant, for instance: The longevity of individual leaves in evergreen plants varies from a few months to several decades (over 30 years in the Great Basin bristlecone pine ). Japanese umbrella pine is unique in that it has its own family of which it is the only species. Evergreen and deciduous species vary in a range of morphological and physiological characters. Generally, broad-leaved evergreen species have thicker leaves than deciduous species, with

7038-772: The evolution of large birds and even reptiles such as the Elephant bird , moa , Haast's eagle , Quinkana , Megalania and Meiolania . The severe climatic changes during the Ice Age had major impacts on the fauna and flora. With each advance of the ice, large areas of the continents became depopulated, and plants and animals retreating southwards in front of the advancing glacier faced tremendous stress. The most severe stress resulted from drastic climatic changes, reduced living space, and curtailed food supply. A major extinction event of large mammals ( megafauna ), which included mammoths , mastodons , saber-toothed cats , glyptodons ,

7140-409: The first day and close in late morning or early afternoon. Then they open as male in the afternoon of the second day. B varieties open as female on the afternoon of the first day, close in late afternoon and reopen as male the following morning. Certain cultivars, such as the 'Hass', have a tendency to bear well only in alternate years. After a season with a low yield, due to factors such as cold (which

7242-487: The fruits are picked while unripe and ripened after harvesting. The nutrient density and extremely high fat content of avocado flesh are useful to a variety of cuisines and are often eaten to enrich vegetarian diets. In major production regions like Chile , Mexico and California the water demands of avocado farms place strain on local resources. Avocado production is also implicated in other externalities , including deforestation and human rights concerns associated with

7344-414: The glacial range, which have their own glacial history depending on latitude, terrain and climate. There is a general correspondence between glacials in different regions. Investigators often interchange the names if the glacial geology of a region is in the process of being defined. However, it is generally incorrect to apply the name of a glacial in one region to another. For most of the 20th century, only

7446-490: The greatest return for their crop, but if the fruit remains unpicked for too long, it falls to the ground. The species is only partially able to self-pollinate because of dichogamy in its flowering. This limitation, added to the long juvenile period, makes the species difficult to breed. Most cultivars are propagated by grafting , having originated from random seedling plants or minor mutations derived from cultivars. Modern breeding programs tend to use isolation plots where

7548-427: The harvest was 2.03 million tonnes in 2017. The states that produce the most are México , Morelos , Nayarit , Puebla , and Michoacan, accounting for 86% of the total. In Michoacán, the cultivation is complicated by the existence of drug cartels that extort protection fees from cultivators. They are reported to exact 2,000 Mexican pesos per hectare from avocado farmers and 1 to 3 pesos/kg of harvested fruit. It

7650-450: The historical terminology was established. Corresponding to the terms glacial and interglacial, the terms pluvial and interpluvial are in use (Latin: pluvia , rain). A pluvial is a warmer period of increased rainfall; an interpluvial is of decreased rainfall. Formerly a pluvial was thought to correspond to a glacial in regions not iced, and in some cases it does. Rainfall is cyclical also. Pluvials and interpluvials are widespread. There

7752-552: The large amounts of material moved about by glaciers. Less common are cave deposits, travertines and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarily in shallow marine basins mostly (but with important exceptions) in areas within a few tens of kilometres of the modern shoreline. In a few geologically active areas such as the Southern California coast, Pleistocene marine deposits may be found at elevations of several hundred metres. The modern continents were essentially at their present positions during

7854-466: The lower Palaeolithic they disappeared, and the only hominin species found in fossilic records is Homo erectus for much of the Pleistocene. Acheulean lithics appear along with Homo erectus , some 1.8 million years ago, replacing the more primitive Oldowan industry used by A. garhi and by the earliest species of Homo . The Middle Paleolithic saw more varied speciation within Homo , including

7956-478: The megafauna and migrated north. Late Pleistocene bighorn sheep were more slender and had longer legs than their descendants today. Scientists believe that the change in predator fauna after the late Pleistocene extinctions resulted in a change of body shape as the species adapted for increased power rather than speed. The extinctions hardly affected Africa but were especially severe in North America where native horses and camels were wiped out. In July 2018,

8058-423: The nutrients are less available to plants. In taiga or boreal forests , it is too cold for the organic matter in the soil to decay rapidly, so the nutrients in the soil are less easily available to plants, thus favoring evergreens. In temperate climates, evergreens can reinforce their own survival; evergreen leaf and needle litter has a higher carbon-nitrogen ratio than deciduous leaf litter , contributing to

8160-577: The older Pliocene Epoch , which Lyell had originally thought to be the youngest fossil rock layer. He constructed the name "Pleistocene" ('most new' or 'newest') from the Greek πλεῖστος ( pleīstos ) 'most' and καινός ( kainós ( Latinized as cænus ) 'new'). This contrasts with the immediately preceding Pliocene ("newer", from πλείων ( pleíōn , "more") and kainós ) and the immediately subsequent Holocene ("wholly new" or "entirely new", from ὅλος ( hólos , "whole") and kainós ) epoch , which extends to

8262-423: The overall demand and supply chain slowed due to labor and shipping restrictions. Later in 2020, demand in the United States and within Mexico increased at a time when American retail prices continued to rise. During 2020 in the United States, month-to-month volume sales of avocados were similar to those of tomatoes at about 250 million pounds (110 million kg) per month. A report issued in mid-2020 forecast that

8364-559: The partial control of their production in Mexico by organized crime . Global warming is expected to result in significant changes to the suitable growing zones for avocados, and place additional pressures on the locales in which they are produced due to heat waves and drought. Persea americana is a tree that grows to 9–20 m (30–66 ft) with a trunk diameter between 0.3–0.6 m (1–2 ft). The leaves are 8–25 cm (3–10 in) long and alternately arranged. Panicles of flowers with deciduous bracts arise from new growth or

8466-448: The plant. The exact temperature which evergreen roots can handle depends on the species, for example, Picea Glauca (White Spruce) roots are killed at −10 °F (−23 °C). In areas where there is a reason for being deciduous, e.g. a cold season or dry season, evergreen plants are usually an adaptation of low nutrient levels. Additionally, they usually have hard leaves and have an excellent water economy due to scarce resources in

8568-624: The pre- Inca city of Chan Chan . The plant was introduced to Spain in 1601, Indonesia around 1750, Mauritius in 1780, Brazil in 1809, the United States mainland in 1825, South Africa and Australia in the late 19th century, and the Ottoman Empire in 1908. In the United States, the avocado was introduced to Florida and Hawaii in 1833 and in California in 1856. The name avocado has been used in English since at least 1764, with minor spelling variants such as avogato attested even earlier. The avocado

8670-465: The presence and consumption of avocado. There is evidence for avocado use at Norte Chico civilization sites in Peru by at least 3,200 years ago and at Caballo Muerto in Peru from around 3,800 to 4,500 years ago. The avocado tree also has a long history of cultivation in Central and South America, likely beginning as early as 5,000 BC. A water jar shaped like an avocado, dating to AD 900, was discovered in

8772-458: The present time. The Pleistocene has been dated from 2.580 million (±0.005) to 11,700 years BP with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation , up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9700 BCE (11,700 calendar years BP). The end of

8874-417: The ratio of O to O (two isotopes of oxygen ) by mass (measured by a mass spectrometer ) present in the calcite of oceanic core samples is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in O , which is included in the tests of the microorganisms ( foraminifera ) contributing the calcite. A more recent version of

8976-564: The revised definition of the Quaternary , by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene. Radiocarbon dating is considered to be inaccurate beyond around 50,000 years ago. Marine isotope stages (MIS) derived from Oxygen isotopes are often used for giving approximate dates. Pleistocene non-marine sediments are found primarily in fluvial deposits , lakebeds, slope and loess deposits as well as in

9078-407: The sampling process makes use of modern glacial ice cores. Although less rich in O than seawater, the snow that fell on the glacier year by year nevertheless contained O and O in a ratio that depended on the mean annual temperature. Temperature and climate change are cyclical when plotted on a graph of temperature versus time. Temperature coordinates are given in the form of

9180-632: The sole factor responsible for the variations in climate since they explain neither the long-term cooling trend over the Plio-Pleistocene nor the millennial variations in the Greenland Ice Cores known as Dansgaard-Oeschger events and Heinrich events. Milankovitch pacing seems to best explain glaciation events with periodicity of 100,000, 40,000, and 20,000 years. Such a pattern seems to fit the information on climate change found in oxygen isotope cores. In oxygen isotope ratio analysis, variations in

9282-421: The study of cyclical climate changes. The glacials in the following tables show historical usages, are a simplification of a much more complex cycle of variation in climate and terrain, and are generally no longer used. These names have been abandoned in favour of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognised since

9384-474: The tissues of the heart, and even death. Birds also seem to be particularly sensitive to this toxic compound. The leaves of the Guatemalan variety of P. americana are toxic to goats, sheep, and horses. Evergreen There are many different kinds of evergreen plants, including trees , shrubs , and vines. Evergreens include: The Latin binomial term sempervirens , meaning "always green", refers to

9486-436: The tree is ready to be sold. Clonal rootstocks are selected for tolerance of specific soil and disease conditions, such as poor soil aeration or resistance to the soil-borne disease (root rot) caused by Phytophthora cinnamomi . Advances in cloning techniques that can produce up to 500 new plants from a single millimetre of tree cutting have the potential to increase the availability of rootstocks. Commercial avocado production

9588-582: The tree ripen on the ground. Generally, the fruit is picked once it reaches maturity; Mexican growers pick 'Hass' avocados when they have more than 23% dry matter, and other producing countries have similar standards. Once picked, avocados ripen in one to two weeks (depending on the cultivar) at room temperature (faster if stored with other fruits such as apples or bananas, because of the influence of ethylene gas). Some supermarkets sell ripened avocados which have been treated with synthetic ethylene to hasten ripening. The use of an ethylene gas "ripening room", which

9690-426: The tropical and Mediterranean climates of many countries. Mexico is the world's leading producer of avocados as of 2020, supplying nearly 30% of the global harvest in that year. The fruit of domestic varieties have smooth, buttery, golden-green flesh when ripe. Depending on the cultivar , avocados have green, brown, purplish, or black skin, and may be pear-shaped, egg-shaped, or spherical. For commercial purposes

9792-674: The two major grower organizations and Calavo Growers is a major distributor. 'Hass' avocado production in Peru encompasses thousands of hectares in central and western Peru. Peru has now become the largest supplier of avocados imported to the European Union and the second largest supplier to Asia and the United States. The country's location near the equator and along the Pacific Ocean creates consistently mild temperatures all year. 'Hass' avocados from Peru are seasonally available to consumers from May through September and are promoted under

9894-732: The two regions and changing ocean circulation patterns, with the onset of glaciation in the Northern Hemisphere occurring around 2.7 million years ago. During the Early Pleistocene (2.58–0.8 Ma), archaic humans of the genus Homo originated in Africa and spread throughout Afro-Eurasia . The end of the Early Pleistocene is marked by the Mid-Pleistocene Transition , with the cyclicity of glacial cycles changing from 41,000-year cycles to asymmetric 100,000-year cycles, making

9996-517: The use of the word 'avocado' was by Hans Sloane , who coined the term, in a 1696 index of Jamaican plants. The word avocado comes from the Spanish aguacate , which derives from the Nahuatl (Mexican) word āhuacatl [aːˈwakat͡ɬ] , which goes back to the proto-Aztecan * pa:wa . In Molina's Nahuatl dictionary "auacatl" is given also as the translation for compañón "testicle", and this has been taken up in popular culture where

10098-774: The worldwide market, which was US$ 13.7 billion in 2018, would recover after the end of the pandemic and rise to US$ 21.6 billion by 2026. Some people have allergic reactions to avocado. There are two main forms of allergy: those with a tree-pollen allergy develop local symptoms in the mouth and throat shortly after eating avocado; the second, known as latex-fruit syndrome, is related to latex allergy and symptoms include generalised urticaria , abdominal pain, and vomiting and can sometimes be life-threatening. Avocado leaves, bark , skin, or pit are documented to be harmful to animals; cats, dogs, cattle, goats, rabbits, rats, guinea pigs, birds, fish, and horses can be severely harmed or even killed when they consume them. The avocado fruit

10200-576: Was 8.1 million tonnes , led by Mexico with 30% (2.4 million tonnes) of the total (table). Other major producers were Colombia , Dominican Republic , Peru , and Indonesia , together producing 35% of the world total. Despite market effects of the 2020 COVID-19 pandemic , volume production of avocados in Mexico increased by 40% over 2019 levels. In 2018, the US Department of Agriculture estimated that 231,028 hectares (570,880 acres) in total were under cultivation for avocado production in Mexico,

10302-543: Was a series of glacials and interglacials, stadials and interstadials, mirroring periodic climate changes. The main factor at work in climate cycling is now believed to be Milankovitch cycles . These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earth's motion. The effects of Milankovitch cycles were enhanced by various positive feedbacks related to increases in atmospheric carbon dioxide concentrations and Earth's albedo. Milankovitch cycles cannot be

10404-536: Was commonly referred to in California as ahuacate and in Florida as alligator pear until 1915, when the California Avocado Association popularized the term avocado. As a subtropical species, avocados need a climate without frost and with little wind. High winds reduce the humidity, dehydrate the flowers, and affect pollination. When even a mild frost occurs, premature fruit drop may occur; although

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