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Phoenix Dactylifera

Phoenix dactylifera

The Date Palm Phoenix dactylifera is a palm, extensively cultivated for its edible fruit. Due to its long history of cultivation for fruit, its exact native distribution is unknown, but the date palm probably originated somewhere in the desert oases of north Africa, and perhaps also southwest Asia. It is a medium-sized tree, 15-25 m tall, often clumped with several trunks from a single root system, but also often growing singly. The leaves are pinnate, up to 3 m long, with spines on the petiole and about 150 leaflets; the leaflets are 30 cm long and 2 cm broad.

History of dates

Dates have been a staple food of the Middle East for thousands of years. The date palm is believed to have originated around the Persian Gulf, and has been cultivated in ancient times from Mesopotamia to prehistoric Egypt, possibly as early as 6000 BC. There is archeological evidence of cultivation in eastern Arabia in 4,000 BC. In later times, Arabs spread dates around northern Africa and into Spain, and dates were introduced into California by the Spaniards in 1765, around Mission San Ignacio.

Fruit

The fruit of the Date Palm is known as a date. They are oval-cylindrical, 3-7 cm long, and 2-3 cm diameter, and when unripe, range from bright red to bright yellow in colour, depending on variety. Dates contain a single seed about 2-2.5 cm long and 6-8 mm thick. Three main types of date exist; soft (Barhee, Halawy, Khadrawy, Medjool), semi-dry (Dayri, Deglet Noor, Zahidi), and dry (Thoory). The type of fruit depends on the glucose, fructose and sucrose content. Dates are naturally wind pollinated, but in modern commercial horticulture are entirely pollinated manually. Natural pollination requires about an equal number of male and female plants. However, with assistance one male can pollenize up to 50 females. Since the males are of value only as pollenizers, this allows the growers to use their resources for many more fruit producing female plants. Some growers do not even maintain any male plants as male flowers become available at local markets at pollination time. Pollination is done by skilled laborers on ladders, or less often the pollen may be blown onto the female flowers by wind machine. Date farmers in Iraq lost their 2003 crop, because the nation was at war during pollination time. Parthenocarpic cultivars are available but the seedless fruit is smaller and of lower quality. Dates ripen in four stages, which are known throughout the world by their Arabic names kimri (unripe), khalal (full-size, crunchy), rutab (ripe, soft), tamr (ripe, sun-dried). A 100 gram portion of fresh dates is a premium source of vitamin C and supplies 230 kcal (960 kJ) of energy. When dried, 100 grams of dates provides 3 grams of dietary fibre and supplies 270 kcal (1130 kJ) of energy. Dates are an important traditional crop in Iraq, Arabia, and north Africa west to Morocco. In Islamic countries, dates and milk are a traditional first meal when the sun sets during Ramadan. Dates (especially Medjool) are also cultivated in southern California in the United States. United States

Cultivars of dates

A large number of date cultivars are grown. The most important are:
- 'Aabel' - common in Libya
- 'Amir Hajj' - from Iraq, these are soft with a thin skin and thick flesh.
- ''Abid Rahim' (Arabic: عبد رحيم‎) - from Sudan
- 'Amer' (amir) hajj - called "the visitor's date"
- 'Barakawi' (Arabic: بركاوي‎) - from Sudan
- 'Barhee' (barhi) (from Arabic barh, a hot wind) - these are nearly cylindrical, light amber to dark brown when ripe; soft, with thick flesh and rich flavor.
- 'Bireir' (Arabic: برير‎) - from Sudan
- 'Deglet Noor' (Arabic: 'translucent') - this is a leading date in Algeria and Tunisia; and in the latter country it is grown in inland oases and is the chief export cultivar. It is semi-dry and not very sweet.
- 'Derrie' or 'Dayri' (the 'Monastery' date) - from southern Iraq - these are long, slender, nearly black, and soft.
- 'Empress'
- 'Ftimi' or 'Alligue' - these are grown in inland oases of Tunisia.
- 'Halawy' (Halawi) (Arabic: 'sweet') - these are soft, and extremely sweet, small to medium in size.
- 'Haleema' - in Hoon, Libya (Haleema is a woman's name)
- 'Hayany' - from Egypt (Hayani) (Hayany is a man's name) - these dates dark-red to nearly black and soft.
- 'Iteema' - common in Algeria
- 'Khadrawy' (Arabic: 'green') - this is the cultivar most favored by Arabs, it is a soft, very dark date considered to be of the highest quality.
- 'Khalasah' (Arabic: 'quintessence')
- 'Khastawi' (Khusatawi, Kustawy) - this is the leading soft date in Iraq; it is syrupy and small in size, prized for dessert.
- 'Maktoom' (Arabic: 'hidden') - this is a large, red-brown, thick-skinned, soft, medium-sweet date.
- 'Manakbir' - a large fruit which ripens early.
- 'Medjool' (Arabic: 'unknown') - from Morocco, also grown in the USA and Israel; a large, sweet and succulent date.
- 'Migraf' (Mejraf) - very popular in Southern Yemen, these are large, golden-amber dates.
- 'Mgmaget Ayuob' - from Hoon, Libya
- 'Mishriq' (Arabic: 'East' - مشرق)‎ - from Sudan and Saudi Arabia
- 'Saidy' (Saidi) - soft, very sweet, these are popular in Libya.
- 'Sayer' (Sayir) (Arabic: 'common') - these dates are dark orange-brown, of medium size, soft and syrupy.
- 'Tagyat' - common in Libya
- 'Tamej' - in Libya
- 'Thoory' (Thuri) - popular in Algeria, this dry date is brown-red when cured with a bluish bloom and very wrinkled skin. Its flesh is sometimes hard and brittle but the flavour described as sweet and nutty.
- 'Umeljwary' - in Libya
- 'Zahidi' (Zahdi) (Arabic: 'nobility'?) - these medium size, cylindrical, light golden-brown semi-dry dates are very sugary, and sold as soft, medium-hard and hard.

Production

World production of dates was approximately 6.7 Mio tonnes in 2004 (FAO statistics [http://apps.fao.org/faostat/form?collection=Production.Crops.Primary&Domain=Production&servlet=1&hasbulk=0&version=ext&language=EN]). The major producers are:
- Egypt: 1,100,000 t (16.2% of world production)
- Iran: 880,000 t (13.0%)
- Saudi Arabia: 830,000 t (12.3%)
- United Arab Emirates: 760,000 t (11.2%)
- Pakistan: 650,000 t (9.6%)
- Algeria: 450,000 t (6.6%)
- Sudan: 330,000 t
- Oman: 240,000 t
- Libya: 140,000 t
- Others: 1,140,000 t
- Iraq used to be a major producer of dates but in recent years production and exports have been curtailed. The First International Date Conference was held in Tripoli, Libya in 1959, and led to the development of a special program under the Food and Agriculture Organisation of the United Nations to promote the commercial utilisation of substandard or physically defective dates.

Food uses of Dates

Dry or soft dates are eaten out-of-hand, or may be seeded and stuffed with fillings such as almonds, candied orange and lemon peel, and marzipan. Dates can also be chopped and used in a range of sweet and savoury dishes: from tajines (tagines) in Morocco to puddings, bread, cakes and other dessert items. Dates are also processed into cubes, paste, spread, date syrup or "honey", powder (date sugar), vinegar or alcohol. Recent innovations include products such as sparkling date juice, used in some Islamic countries as a non-alcoholic version of champagne, for special occasions and religious times such as Ramadan. Dates can also be dehydrated, ground and mixed with grain to form a nutritious stockfeed. Dried dates are fed to camels, horses and dogs in the Sahara desert. In northern Nigeria, dates and peppers added to the native beer are believed to make it less intoxicating. Young date leaves are cooked and eaten as a vegetable, as is the terminal bud or heart, though its removal kills the palm. In India, date seeds are roasted, ground, and used to adulterate coffee. The finely ground seeds are mixed with flour to make bread in times of scarcity. In North Africa, Ghana and the Ivory Coast, date palms are tapped for the sweet sap which is converted into palm sugar, molasses or alcoholic beverages.

Other uses of Date Palms

Date seeds are soaked and ground up for animal feed. Their oil is suitable for use in soap and cosmetic products. They can also be processed chemically as a source of oxalic acid. The seeds are also burned to make charcoal for silversmiths, and can be strung in necklaces. Date Palm leaves are used for Palm Sunday in the Christian religion. In North Africa, they are commonly used for making huts. Mature leaves are also made into mats, screens, baskets and fans. Processed leaves can be used for insulating board. Dried leaf petioles are a source of cellulose pulp, used for walking sticks, brooms, fishing floats and fuel. Leaf sheaths are prized for their scent, and fibre from them is also used for rope, coarse cloth and large hats. Stripped fruit clusters are used as brooms. In Pakistan, a viscous, thick syrup made from the ripe fruits is used as a coating for leather bags and pipes to prevent leaking. Date palm wood is used for posts and rafters for huts; it is lighter than coconut and not very durable. It is also used for construction such as bridges and aqueducts, and parts of dhows. Left over wood is burnt for fuel. Date Palm leaves are used as a lulav in the Jewish holiday of Sukkot.

Traditional Medicinal Uses

Dates have a high tannin content and are used medicinally as a detersive and astringent in intestinal troubles. As an infusion, decoction, syrup or paste, is administered for sore throat, colds, bronchial catarrh, and taken to relieve fever and number of other complaints. One traditional belief is that it can counteract alcohol intoxication. The seed powder is also used in some traditional medicines. A gum that exudes from the wounded trunk is employed in India for treating diarrhea and genito-urinary ailments. The roots are used against toothache. The pollen yields an estrogenic principle, estrone, and has a gonadotropic effect on young rats.

Diseases

Date Palms are susceptible to a disease called Bayoud disease which is caused by the fungus Fusarium oxysporum. This disease, which kills many of the popular older cultivars like 'Deglet Noor', has led to a major decline in production where it is present, notably Morocco and western Algeria. New cultivars resistant to the disease are however being developed.

External links

- [http://www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/006/Y4360E/y4360e00.HTM Date Palm Cultivation] (Food and Agriculture Organization)
- [http://www.hort.purdue.edu/newcrop/morton/Date.html Fruits of Warm Climates: Date]
- Nutrition information for [http://www.kallipolis.com/diet/food.php?id=9421 medjool] and [http://www.kallipolis.com/diet/food.php?id=9087&w=2 deglet noor] dates. Category:Palms Category:Fruit ja:ナツメヤシ simple:Date Palm

Arecaceae

Many; see list of Arecaceae genera Arecaceae (also known as Palmae), the Palm Family, is a family of flowering plants, belonging to the monocot order, Arecales. There are 202 currently known genera with around 2,600 species, most of which are restricted to tropical or subtropical climates. Of all the families of plants, the Arecaceae is the most easily recognizable as distinct by most persons. The type member of this family is the areca palm, the fruit of which is chewed with the betel leaf and often confused with it. The Date Palm, Rattan, and Coconut also belong to this family. Palm oil is an edible vegetable oil produced by the oil palms in the genus Elaeis. Several species are harvested for heart of palm. Palm sap is sometimes fermented to produce palm wine. The Palm Sunday festival uses palms, hence the name. Palms first appear in the fossil record around 70-80 million years ago, during the Cretaceous Period, making them one of the older families of flowering plants. Economically important genera include:
- Areca
- Arenga
- Attalea
- Bactris
- Borassus (Palmyra Palm)
- Calamus - rattan palm
- Cocos - coconut
- Copernicia - carnauba wax palm
- Elaeis - oil palm
- Euterpe Cabbage Heart Palm, and Açaí Palm
- Jessenia
- Jubaea Chilean Wine Palm and Coquito Palm
- Orbignya
- Phoenix - date palms
- Rhapis
- Roystonea - royal palm
- Sabal - palmetto
- Salacca - salak
- Trachycarpus
- Veitchia
- Wallichia
- Washingtonia See list of Arecaceae genera for a complete listing. list of Arecaceae genera list of Arecaceae genera Few palms tolerate severe cold, and the majority of the species are tropical or subtropical. The most cold-tolerant are Trachycarpus, native to eastern Asia, and Rhapidophyllum, native to the southeastern United States. For more details, see hardy palms. In the United States, different types of palm trees can be seen in tropical and mediterranean climate areas, such as Florida, (southern) California and Hawaii and along the Gulf Coast through southern Georgia, Mississippi, Alabama, and Louisiana to Texas. The southeastern state of South Carolina is nicknamed the Palmetto State because of the number of palms that line the state's Atlantic coast. Some palms can be grown as far north as Maryland, Arkansas, and even up along the Pacific coast to Oregon and Washington. There have even been known species of transplanted palms that have survived as far north as southern New Jersey [http://www.bg-map.com/palms/woodbury.html]. The desert areas of Nevada, Arizona, Utah and New Mexico are also home to some native palms. Southern Europe has two native palms, Chamaerops humilis (widespread, but mainly seen in Portugal, Spain, France, Italy and Malta) and Phoenix theophrastii (Crete; also southern Turkey). Many other palms are widely planted, with the Japanese Trachycarpus wagnerianus being grown successfully as far north as Iceland.

References

- C. H. Schultz-Schultzenstein (1832). Natürliches System des Pflanzenreichs..., 317. Berlin, Germany.
- N. W. Uhl, J. Dransfield (1987). Genera palmarum: a classification of palms based on the work of Harold E. Moore, Jr. (Allen Press, Lawrence, Kansas)

External links

- [http://www.kew.org/cgi-bin/web.dbs/genlist.pl?PALMAE Kew Botanic Garden's Palm Genera list] A list of the currently acknowledged genera by Kew Royal Botanic Gardens in London, England.
- [http://www.plantapalm.com/vpe/taxonomy/vpe_taxonomy3.htm Taxonomy of the family Arecaceae]
- [http://www.pacsoa.org.au/palms/ PACSOA] Palm and Cycad Societies of Australia palm species listing with images.
- [http://www.plantapalm.com/vpe/photos/vpe_photos.htm Plant a Palm] A website with a large amount of information on palms, their cultivation and uses. This link goes to the photo gallery via species listing. Category:Plant families Category:Palms ja:ヤシ (植物) th:ปาล์ม

Desert

In geography, a desert is a landscape form or region that receives little precipitation - less than 250 mm per year. Deserts have a reputation for supporting very little life. Compared to wetter regions this may be true, although upon closer examination, deserts often harbor a wealth of life that usually remains hidden (especially during the daylight) to preserve moisture. Approximately one-third of Earth's land surface is desert. (See a map of the world's non-polar deserts, http://pubs.usgs.gov/gip/deserts/what/world.html.) Desert landscapes have certain common features. Desert soil is often composed mostly of rocky surfaces called regs. Sand dunes called ergs and stony or hamada surfaces compose the minority of desert surfaces. Exposures of rocky terrain are typical, and reflect minimal soil development and sparseness of vegetation. Bottom lands may be salt-covered flats. Eolian (wind-driven) processes are major factors in shaping desert landscapes. Deserts sometimes contain valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Because deserts are dry, they are ideal places for human artifacts and fossils to be preserved. In the Köppen climate classification system, they are classed as (BW).

Types of desert

Most classifications rely on some combination of the number of days of rainfall, the total amount of annual rainfall, temperature, humidity, or other factors. In 1953, Peveril Meigs divided desert regions on Earth into three categories according to the amount of precipitation they received. In this now widely accepted system, extremely arid lands have at least 12 consecutive months without rainfall, arid lands have less than 250 millimeters of annual rainfall, and semiarid lands have a mean annual precipitation of between 250 and 500 millimeters. Arid and extremely arid land are deserts, and semiarid grasslands generally are referred to as steppes. However, lack of rainfall alone can't provide an accurate description of what a desert is. For example, Phoenix, Arizona receives less than 250 millimeters, (10 inches), of precipitation per year, and is immediately recognized as being located in a desert. The North Slope of Alaska's Brooks Range also receives less than 250 millimeters of precipitation per year, but is not generally recognized as a desert region. The difference lies in something termed "potential evapotranspiration." The water budget of an area can be calculated using the formula P-PE+/-S, whereby P is precipitation, PE is potential evapotranspiration rates and S is amount of surface storage of water. Evapotranspiration is the combination of water loss through atmospheric evaporation, coupled with the evaporative loss of water through the life processes of plants. Potential evapotranspiration, then, is the amount of water that could evaporate in any given region. Tucson, Arizona receives about 300 millimeters, (12 inches), of rain per year, however about 2500 millimeters, (100 inches), of water could evaporate over the course of a year. In other words, about 8 times more water could evaporate from the region than actually falls. Rates of evapotranspiration in other regions such as Alaska are much lower, so while these regions receive minimal precipitation, they should be designated as specifically different from the simple definition of a desert: a place where evaporation exceeds precipitation. That said, there are different forms of deserts. Cold deserts can be covered in snow; such locations don't receive much precipitation, and what does fall remains frozen as snow pack; these are more commonly referred to as tundra if a short season of above-freezing temperatures is experienced, or as an ice cap if the temperature remains below freezing year-round, rendering the land almost completely lifeless. Most non-polar deserts are hot because they have little water. Water tends to have a cooling, or at least a moderating, effect in environments where it is plentiful. In some parts of the world deserts are created by a rain shadow effect in which air masses lose much of their moisture as they move over a mountain range; other areas are arid by virtue of being very far from the nearest available sources of moisture (this is true in some middle-latitude landmass interior locations, particularly in Asia). Deserts are also classified by their geographical location and dominant weather pattern as trade wind, midlatitude, rain shadow, coastal, monsoon, or polar deserts. Former desert areas presently in nonarid environments are paleodeserts, and extraterrestrial deserts exist on other planets.

Montane deserts

Montane deserts are arid places with a very high altitude; the most prominent example is found north of the Himalaya, in parts of the Kunlun Mountains and the Tibetan Plateau. Many locations within this category have elevations exceeding 3,000 meters (9,843 feet) and the thermal regime can be hemiboreal. These places owe their profound aridity (the average annual precipitation is often less than 40mm) to being very far from the nearest available sources of moisture.

Desert features

hemiboreal] Sand covers only about 20 percent of Earth's deserts. Most of the sand is in sand sheets and sand seas—vast regions of undulating dunes resembling ocean waves "frozen" in an instant of time. In general, there are 6 forms of deserts: i.Mountain and basin deserts, ii. Hamada deserts, which comprise of a plateaux landforms, iii. Regs which consist of rock pavements, iv. Ergs which are formed by sand seas, v. Intermontane Basins, and vi. Badlands which are located at the margins of arid lands comprising of clay-rich soil. Nearly 100 percent of desert surfaces are plains where eolian deflation—removal of fine-grained material by the wind—has exposed loose gravels consisting predominantly of pebbles but with occasional cobbles. The remaining surfaces of arid lands are composed of exposed bedrock outcrops, desert soils, and fluvial deposits including alluvial fans, playas, desert lakes, and oases/oasis. Bedrock outcrops commonly occur as small mountains surrounded by extensive erosional plains. There are several different types of dunes. Barchan dunes are produced by strong winds blowing across a level surface and are crescent shaped. Longitudinal or seif dunes are dunes that are parallel to a strong wind that blows in one general direction. Transverse dunes run are a right angle to the constant wind direction. Star dunes are star-shaped and have several ridges that spread out around a point. Oases are vegetated areas moistened by springs, wells, or by irrigation. Many are artificial. Oases are often the only places in deserts that support crops and permanent habitation.

Soils

irrigation Soils that form in arid climates are predominantly mineral soils (classified as Aridisols) with low organic content such as salt. The repeated accumulation of water in some soils causes distinct salt layers to form. Calcium carbonate precipitated from solution may cement sand and gravel into hard layers called "calcrete" that form layers up to 50 meters thick. Caliche is a reddish-brown to white layer found in many desert soils. Caliche commonly occurs as nodules or as coatings on mineral grains formed by the complicated interaction between water and carbon dioxide released by plant roots or by decaying organic material.

Vegetation

Most desert plants are drought- or salt-tolerant, such as xerophytes. Some store water in their leaves, roots, and stems. Other desert plants have long tap roots that penetrate the water table, anchor the soil, and control erosion. The stems and leaves of some plants lower the surface velocity of sand-carrying winds and protect the ground from erosion. Deserts typically have a plant cover that is sparse but enormously diverse. The Sonoran Desert of the American Southwest has the most complex desert vegetation on Earth. The giant saguaro cacti provide nests for desert birds and serve as "trees" of the desert. Saguaro grow slowly but may live 200 years. When 9 years old, they are about 15 centimeters high. After about 75 years, the cacti develop their first branches. When fully grown, saguaro are 15 meters tall and weigh as much as 10 tons. They dot the Sonoran and reinforce the general impression of deserts as cacti-rich land. Although cacti are often thought of as characteristic desert plants, other types of plants have adapted well to the arid environment. They include the pea family and sunflower family. Cold deserts have grasses and shrubs as dominant vegetation.

Water

sunflower Rain does fall occasionally in deserts, and desert storms are often violent. A record 44 millimeters of rain once fell within 3 hours in the Sahara. Large Saharan storms may deliver up to 1 millimeter per minute. Normally dry stream channels, called arroyos or wadis, can quickly fill after heavy rains, and flash floods make these channels dangerous. Though little rain falls in deserts, deserts receive runoff from ephemeral, or short-lived, streams fed by rain and snow from adjacent highlands. These streams fill the channel with a slurry of mud and commonly transport considerable quantities of sediment for a day or two. Although most deserts are in basins with closed, or interior drainage, a few deserts are crossed by 'exotic' rivers that derive their water from outside the desert. Such rivers infiltrate soils and evaporate large amounts of water on their journeys through the deserts, but their volumes are such that they maintain their continuity. The Nile River, the Colorado River, and the Yellow River are exotic rivers that flow through deserts to deliver their sediments to the sea. Lakes form where rainfall or meltwater in interior drainage basins is sufficient. Desert lakes are generally shallow, temporary, and salty. Because these lakes are shallow and have a low bottom gradient, wind stress may cause the lake waters to move over many square kilometers. When small lakes dry up, they leave a salt crust or hardpan. The flat area of clay, silt, or sand encrusted with salt that forms is known as a playa. There are more than a hundred playas in North American deserts. Most are relics of large lakes that existed during the last ice age about 12,000 years ago. Lake Bonneville was a 52,000-square-kilometer lake almost 300 meters deep in Utah, Nevada, and Idaho during the Ice Age. Today the remnants of Lake Bonneville include Utah's Great Salt Lake, Utah Lake, and Sevier Lake. Because playas are arid land forms from a wetter past, they contain useful clues to climatic change. When the occassional preticipation does occur, it erodes the desert rocks quickly and powerfully. Wind is the other factor that erodes deserts- they are constant yet slow. The flat terrains of hardpans and playas make them excellent race tracks and natural runways for airplanes and spacecraft. Ground-vehicle speed records are commonly established on Bonneville Speedway, a race track on the Great Salt Lake hardpan. Space shuttles land on Rogers Lake Playa at Edwards Air Force Base, California.

Mineral resources

Some mineral deposits are formed, improved, or preserved by geologic processes that occur in arid lands as a consequence of climate. Ground water leaches ore minerals and redeposits them in zones near the water table. This leaching process concentrates these minerals as ore that can be mined. Evaporation in arid lands enriches mineral accumulation in their lakes. Playas may be sources of mineral deposits formed by evaporation. Water evaporating in closed basins precipitates minerals such as gypsum, salts (including sodium nitrate and sodium chloride), and borates. The minerals formed in these evaporite deposits depend on the composition and temperature of the saline waters at the time of deposition. Significant evaporite resources occur in the Great Basin Desert of the United States, mineral deposits made forever famous by the "20-mule teams" that once hauled borax-laden wagons from Death Valley to the railroad. Boron, from borax and borate evaporites, is an essential ingredient in the manufacture of glass, ceramics, enamel, agricultural chemicals, water softeners, and pharmaceuticals. Borates are mined from evaporite deposits at Searles Lake, California, and other desert locations. The total value of chemicals that have been produced from Searles Lake substantially exceeds US$1 billion. The Atacama Desert of South America is unique among the deserts of the world in its great abundance of saline minerals. Sodium nitrate has been mined for explosives and fertilizer in the Atacama since the middle of the 19th century. Nearly 3 million tonnes were mined during World War I. Valuable minerals located in arid lands include copper in the United States, Chile, Peru, and Iran; iron and lead-zinc ore in Australia; chromite in Turkey; and gold, silver, and uranium deposits in Australia and the United States. Nonmetallic mineral resources and rocks such as beryllium, mica, lithium, clays, pumice, and scoria also occur in arid regions. Sodium carbonate, sulfate, borate, nitrate, lithium, bromine, iodine, calcium, and strontium compounds come from sediments and near-surface brines formed by evaporation of inland bodies of water, often during geologically recent times. The Green River Formation of Colorado, Wyoming, and Utah contains alluvial fan deposits and playa evaporites created in a huge lake whose level fluctuated for millions of years. Economically significant deposits of trona, a major source of sodium compounds, and thick layers of oil shale were created in the arid environment. Some of the more productive petroleum areas on Earth are found in arid and semiarid regions of Africa and the Mideast, although the oil fields were originally formed in shallow marine environments. Recent climate change has placed these reservoirs in an arid environment. Other oil reservoirs, however, are presumed to be eolian in origin and are presently found in humid environments. The Rotliegendes, a hydrocarbon reservoir in the North Sea, is associated with extensive evaporite deposits. Many of the major U.S. hydrocarbon resources may come from eolian sands. Ancient alluvial fan sequences may also be hydrocarbon reservoirs.

List of deserts

Americas

- Atacama desert in Chile
- Mojave, Great Basin, Sonoran, and Chihuahuan See also: List of North American deserts

Africa

- Libyan
- Kalahari
- Sahara
- Namib

Asia-Pacific

- Dasht-e Kavir, central Iran.
- Gobi desert of Mongolia; Taklamakan desert in China.
- Kara Kum deserts in Central Asia.
- Thar-Cholistan desert in India and Pakistan.
- Kavir-e Lut, souteast Iran.
- Kyzyl Kum - Kazakhstan and Uzbekistan
- Negev - southern Israel
- Judean Desert - eastern Israel and Palestine
- Simpson Desert, Great Sandy Desert, Sturt's Stony Desert, Tanami Desert, Great Victoria Desert, Big Desert, Little Desert (all in Australia)
- Taklamakan - Xinjiang Uighur Autonomous Region of the People's Republic of China
- Rangipo Desert - New Zealand

Oasis

:For other senses of this word, see oasis (disambiguation), and for the band, see Oasis (band). Oasis (band)] In geography, an oasis is an isolated area of vegetation in a desert, typically surrounding a spring or similar water source. The location of oases has been of critical importance for trade and transportation routes in desert areas. Caravans must travel via oases in order that supplies of water and food can be replenished. Thus, political or military control of an oasis has in many cases meant control of trade on a particular route. For example, the oases of Awjila, Ghadames and Kufra, situated in modern-day Libya, have at various times been vital to both North-South and East-West trade in the Sahara desert. The word oasis is from Greek ὄασις oasis, which according to some borrowed it directly from Egyptian wḥ3t or Demotic wḥỉ, while according to others borrowed it from Egyptian through Coptic ouaḥe (
- /waħe/).

Oases include

- Kufra Oasis, Libya
- Safsaf Oasis, Egypt
- Siwa Oasis, Egypt
- Tabas, Iran
- Turpan, Xinjiang, China
- El Tour, Sinai, Egypt Category:Landforms ja:オアシス

Tree

, the tallest tree species on earth]] A tree can be defined as a large, perennial, woody plant. Though there is no set definition regarding minimum size, the term generally applies to plants at least 6 m (20 ft) high at maturity and, more importantly, having secondary branches supported on a single main stem or trunk (see shrub for comparison). Compared with most other plant forms, trees are long-lived. A few species of trees grow to 100 m tall, and some can live for several thousand years. Trees are important components of the natural landscape and significant elements in landscaping, and in agriculture supplying orchard crops (such as apples). Trees also play an important role in many of the world's mythologies (see Tree (mythology)).

Classifications

Tree (mythology)]] A tree is a plant form and trees occur in many different orders and families of plants. Trees thus show a wide variety of growth form, leaf type and shape, bark characteristics, reproductive structures, etc. The earliest trees were tree ferns and horsetails, which grew in vast forests in the Carboniferous Period; tree ferns still survive, but the only surviving horsetails are not of tree form. Later, in the Triassic Period, conifers, ginkgos, cycads and other gymnosperms appeared, and subsequently flowering plants in the Cretaceous Period. Most species of trees today are flowering plants and conifers. The listing below gives examples of many well-known trees and how they are typically classified. A small group of trees growing together is called a grove or copse, and a landscape covered by a dense growth of trees is called a forest. Several biotopes are defined largely by the trees that inhabit them; examples are rainforest and taiga (see ecozones). A landscape of trees scattered or spaced across grassland (usually grazed or burned over periodically) is called a savanna.

Morphology

The basic parts of a tree are the roots, trunk(s), branches, twigs and leaves. Tree stems consist mainly of support and transport tissues (xylem and phloem). Wood consists of xylem cells, and bark is made of phloem and other tissues external to the vascular cambium. Trees may be broadly grouped into exogenous and endogenous trees according to the way in which their stem diameter increases. Exogenous trees, which comprise the great majority of modern trees (all conifers, and all broadleaf trees), grow by the addition of new wood outwards, immediately under the bark. Endogenous trees, mainly in the monocotyledons (e.g. palms), grow by addition of new material inwards. As an exogenous tree grows, it creates growth rings. In temperate climates, these are commonly visible due to changes in the rate of growth with temperature variation over an annual cycle. These rings can be counted to determine the age of the tree, and used to date cores or even wood taken from trees in the past; this practice is known as the science of dendrochronology. In some tropical regions with constant year-round climate, growth is continuous and distinct rings are not formed, so age determination is impossible. Age determination is also impossible in endogenous trees. dendrochronology, Chile]] The roots of a tree are generally embedded in earth, providing anchorage for the above-ground biomass and absorbing water and nutrients from the soil. Above ground, the trunk gives height to the leaf-bearing branches, aiding in competition with other plant species for sunlight. In many trees, the arrangement of the branches optimizes exposure of the leaves to sunlight. Not all trees have all the plant organs or parts mentioned above. For example, most palm trees are not branched, the saguaro cactus of North America has no functional leaves, tree ferns do not produce bark, etc. Based on their general shape and size, all of these are nonetheless generally regarded as trees. Indeed, sometimes size is the more important consideration. A plant form that is similar to a tree, but generally having smaller, multiple trunks and/or branches that arise near the ground, is called a shrub. However, no sharp differentiation between shrubs and trees is possible. Given their small size, bonsai plants would not technically be 'trees', but one should not confuse reference to the form of a species with the size or shape of individual specimens. A spruce seedling does not fit the definition of a tree, but all spruces are trees. Bamboos by contrast, do show most of the characteristics of trees, yet are rarely called trees.

Champion trees

The world's champion trees can be considered on several factors; height, trunk diameter or girth, total size, and age. It is significant that in each case, the top position is always held by a conifer, though a different species in each case; in most measures, the second to fourth places are also held by conifers. ;Tallest trees The heights of the tallest trees in the world have been the subject of considerable dispute and much (often wild) exaggeration. Modern verified measurement with laser rangefinders combined with tape drop measurements made by tree climbers, carried out by the [http://www.uark.edu/misc/ents/home.htm U.S. Eastern Native Tree Society] has shown that most older measuring methods and measurements are unreliable, often producing exaggerations of 5% to 15% above the real height. Historical claims of trees of 114 m, 117 m, 130 m, and even 150 m, are now largely disregarded as unreliable, fantasy or outright fraud. The following are now accepted as the top five tallest reliably measured species: # Coast Redwood Sequoia sempervirens: 112.83 m, Humboldt Redwoods State Park, California ([http://www.conifers.org/cu/se/index.htm Gymnosperm Database]) # Coast Douglas-fir Pseudotsuga menziesii: 100.3 m, Brummit Creek, Coos County, Oregon ([http://www.conifers.org/pi/ps/menziesii2.htm Gymnosperm Database]) # Sitka Spruce Picea sitchensis: 96.7 m, Prairie Creek Redwoods State Park, California ([http://www.conifers.org/pi/pic/sitchensis.htm Gymnosperm Database]) # Giant Sequoia Sequoiadendron giganteum: 93.6 m, Redwood Mountain Grove, California ([http://www.conifers.org/cu/se2/index.htm Gymnosperm Database]) # Australian Mountain-ash Eucalyptus regnans: 92.0 m, Styx Valley, Tasmania ([http://www.forestrytas.com.au/forestrytas/tasfor/tasforests_12/tasfor_12_09.pdf Forestry Tasmania] [pdf file]) ;Stoutest trees The girth (circumference) of a tree is – or at least should be – much easier to measure than the height, as it is a simple matter of stretching a tape round the trunk, and pulling it taut to find the circumference. Despite this, U.K. tree author Alan Mitchell made the following comment about measurements of yew trees in the British Isles: :"The aberrations of past measurements of yews are beyond belief. For example, the tree at Tisbury has a well-defined, clean, if irregular bole at least 1.5 m long. It has been found to have a girth which has dilated and shrunk in the following way: 11.28 m (1834 Loudon), 9.3 m (1892 Lowe), 10.67 m (1903 Elwes and Henry), 9.0 m (1924 E. Swanton), 9.45 m (1959 Mitchell) .... Earlier measurements have therefore been omitted". As a general standard, tree girth is taken at 'breast height'; this is defined differently in different situations, with most foresters measuring girth at 1.3 m above ground, while ornamental tree measurers usually measure at 1.5 m above ground; in most cases this makes little difference to the measured girth. On sloping ground, the "above ground" reference point is usually taken as the highest point on the ground touching the trunk, but some use the average between the highest and lowest points of ground. Some of the inflated old measurements may have been taken at ground level. Some past exaggerated measurements also result from measuring the complete next-to-bark measurement, pushing the tape in and out over every crevice and buttress. Modern trends are to cite the tree's diameter rather than the circumference; this is obtained by dividing the measured circumference by π; it assumes the trunk is circular in cross-section (an oval or irregular cross-section would result in a mean diameter slightly greater than the assumed circle). This is cited as dbh (diameter at breast height) in tree literature. A further problem with measuring baobabs Adansonia is that these trees store large amounts of water in the very soft wood in their trunks. This leads to marked variation in their girth over the year, swelling to a maximum at the end of the rainy season, minimum at the end of the dry season. Although baobabs have some of the highest girth measurements of any trees, no accurate measurements are currently available, but probably do not exceed 10-11 m diameter. The stoutest species in diameter, excluding baobabs, are: # Montezuma Cypress Taxodium mucronatum: 11.42 m, Árbol del Tule, Santa Maria del Tule, Oaxaca, Mexico (A. F. Mitchell, International Dendrology Society Year Book 1983: 93, 1984). # Giant Sequoia Sequoiadendron giganteum: 8.85 m, General Grant tree, Grant Grove, California ([http://www.conifers.org/cu/se2/index.htm Gymnosperm Database]) # Coast Redwood Sequoia sempervirens: 7.44 m, Prairie Creek Redwoods State Park, California ([http://www.conifers.org/cu/se/index.htm Gymnosperm Database]) ;Largest trees The largest trees in total volume are those which are both tall and of large diameter, and in particular, which hold a large diameter high up the trunk. Measurement is very complex, particularly if branch volume is to be included as well as the trunk volume, so measurements have only been made for a small number of trees, and generally only for the trunk. No attempt has ever been made to include root volume. The top four species measured so far are ([http://www.conifers.org/topics/biggest.htm Gymnosperm Database]): # Giant Sequoia Sequoiadendron giganteum: 1489 m³, General Sherman tree # Coast Redwood Sequoia sempervirens: 1045 m³, Del Norte Titan tree # Western Redcedar Thuja plicata: 500 m³, Quinault Lake Redcedar # Kauri Agathis australis: 400 m³, Tane Mahuta tree (total volume, including branches, 516.7 m³)
However, the Alerce Fitzroya cupressoides, as yet un-measured, may well slot in at third or fourth place, and Montezuma Cypress Taxodium mucronatum is also likely to be high in the list. The largest angiosperm tree is a Australian Mountain-ash, the 'El Grande' tree of about 380 m³ in Tasmania. ;Oldest trees The oldest trees are determined by growth ring counts in cores taken from the edge to the centre of the tree or from entire cross-sections. Accurate determination is only possible for trees which produce growth rings, generally those which occur in seasonal climates; trees in uniform non-seasonal tropical climates grow continuously and do not have distinct growth rings. It is also only possible for trees which are solid to the centre of the tree; many very old trees become hollow as the dead heartwood decays away. For some of these species, age estimates have been made on the basis of extrapolating current growth rates, but the results are usually little better than guesswork or wild speculation. The verified oldest measured ages are ([http://www.conifers.org/topics/oldest.htm Gymnosperm Database]): # Great Basin Bristlecone Pine Pinus longaeva: 4844 years # Alerce Fitzroya cupressoides: 3622 years # Giant Sequoia Sequoia sempervirens: 3266 years # Huon-pine Lagarostrobos franklinii: 2500 years # Rocky Mountains Bristlecone Pine Pinus aristata: 2435 years Other species suspected of reaching exceptional age include European Yew Taxus baccata (probably over 3000 years) and Western Redcedar Thuja plicata. The oldest verified age for an angiosperm tree is 2293 years for the Sri Maha Bodhi Sacred Fig (Ficus religiosa) planted in 288 BC at Anuradhapura, Sri Lanka; this is also the oldest human-planted tree with a known planting date.

Major tree genera

Flowering plants (Magnoliophyta; angiosperms)

Dicotyledons (Magnoliopsida; broadleaf or hardwood trees)

- Anacardiaceae (Cashew family)
- Cashew, Anacardium occidentale
- Mango, Mangifera indica
- Pistachio, Pistacia vera
- Sumac, Rhus species
- Lacquer tree, Toxicodendron verniciflua
- Annonaceae (Custard apple family)
- Cherimoya Annona cherimola
- Custard apple Annona reticulata
- Pawpaw Asimina triloba
- Soursop Annona muricata
- Apocynaceae (Dogbane family)
- Pachypodium Pachypodium species
- Aquifoliaceae (Holly family)
- Holly, Ilex species
- Araliaceae (Ivy family)
- Kalopanax, Kalopanax pictus Kalopanax tree (background) in fall]]
- Betulaceae (Birch family)
- Alder, Alnus species
- Birch, Betula species
- Hornbeam, Carpinus species
- Hazel, Corylus species
- Bignoniaceae (family)
- Catalpa, Catalpa species
- Cactaceae (Cactus family)
- Saguaro, Carnegiea gigantea
- Cannabaceae (Cannabis family)
- Hackberry, Celtis species
- Cornaceae (Dogwood family)
- Dogwood, Cornus species
- Dipterocarpaceae family
- Garjan Dipterocarpus species
- Sal Shorea species
- Ericaceae (Heath family)
- Arbutus, Arbutus species
- Eucommiaceae (Eucommia family)
- Eucommia Eucommia ulmoides
- Fabaceae (Pea family)
- Acacia, Acacia species
- Honey locust, Gleditsia triacanthos
- Black locust, Robinia pseudoacacia
- Laburnum, Laburnum species
- Pau Brasil, Brazilwood, Caesalpinia echinata
- Fagaceae (Beech family )
- Chestnut, Castanea species
- Beech, Fagus species
- Southern beech, Nothofagus species
- Tanoak, Lithocarpus densiflorus
- Oak, Quercus species
- Fouquieriaceae (Boojum family)
- Boojum, Fouquieria columnaris
- Hamamelidaceae (Witch-hazel family)
- Sweetgum, Liquidambar species
- Persian Ironwood, Parrotia persica
- Juglandaceae (Walnut family)
- Walnut, Juglans species
- Hickory, Carya species
- Wingnut, Pterocarya species
- Lauraceae (Laurel family)
- Cinnamon Cinnamomum zeylanicum
- Bay Laurel Laurus nobilis
- Avocado Persea americana
- Lecythidaceae (Paradise nut family)
- Brazil Nut Bertholletia excelsa
- Lythraceae Loosestrife family
- Crape-myrtle Lagerstroemia species
- Magnoliaceae (Magnolia family)
- Tulip tree, Liriodendron species
- Magnolia, Magnolia species
- Malvaceae (Mallow family; including Tiliaceae and Bombacaceae) Bombacaceae
- Baobab, Adansonia species
- Silk-cotton tree, Bombax species
- Bottletrees, Brachychiton species
- Kapok, Ceiba pentandra
- Durian, Durio zibethinus
- Balsa, Ochroma lagopus
- Cacao (cocoa), Theobroma cacao
- Linden (Basswood, Lime), Tilia species
- Meliaceae (Mahogany family)
- Neem, Azadirachta indica
- Bead tree, Melia azedarach
- Mahogany, Swietenia mahagoni
- Moraceae (Mulberry family)
- Fig, Ficus species
- Mulberry, Morus species
- Myristicaceae (Nutmeg family)
- Nutmeg, Mysristica fragrans
- Myrtaceae (Myrtle family)
- Eucalyptus, Eucalyptus species
- Myrtle, Myrtus species
- Guava, Psidium guajavaGuava in flower]]
- Nyssaceae (Tupelo family; sometimes included in Cornaceae)
- Tupelo, Nyssa species
- Dove tree, Davidia involucrata
- Oleaceae (Olive family)
- Olive, Olea europaea
- Ash, Fraxinus species
- Paulowniaceae (Paulownia family)
- Foxglove Tree, Paulownia species
- Platanaceae (Plane family)
- Plane, Platanus species
- Rhizophoraceae (Mangrove family)
- Red Mangrove, Rhizophora mangle
- Rosaceae (Rose family)
- Rowans, Whitebeams, Service Trees Sorbus species
- Hawthorn, Crataegus species
- Pear, Pyrus species
- Apple, Malus species
- Almond, Prunus dulcis
- Peach, Prunus persica
- Plum, Prunus domestica
- Cherry, Prunus species
- Rubiaceae (Bedstraw family)
- Coffee, Coffea species
- Rutaceae (Rue family)
- Citrus, Citrus species
- Cork-tree, Phellodendron species
- Euodia, Tetradium species
- Salicaceae (Willow family)
- Aspen, Populus species
- Poplar, Populus species
- Willow, Salix species Willow
- Sapindaceae (including Aceraceae, Hippocastanaceae) (Soapberry family)
- Maple, Acer species
- Buckeye, Horse-chestnut, Aesculus species
- Mexican Buckeye, Ungnadia speciosa
- Lychee, Litchi sinensis
- Golden rain tree, Koelreuteria paniculata
- Sapotaceae (Sapodilla family)
- Gutta-percha, Palaquium species
- Tambalacoque, or "dodo tree", Sideroxylon grandiflorum, previously Calvaria major
- Simaroubaceae family
- Tree of heaven, Ailanthus species
- Theaceae (Camellia family)
- Gordonia, Gordonia species
- Stuartia, Stuartia species
- Thymelaeaceae (Thymelaea family)
- Ramin, Gonystylus species
- Ulmaceae (Elm family)
- Elm, Ulmus species
- Zelkova, Zelkova species
- Verbenaceae family
- Teak, Tectona species

Monocotyledons (Liliopsida)

Monocotyledon
- Agavaceae (Agave family)
- Cabbage tree, Cordyline australis
- Dragon tree, Dracaena draco
- Joshua tree, Yucca brevifolia
- Arecaceae (Palmae) (Palm family)
- Areca Nut, Areca catechu
- Coconut Cocos nucifera
- Date Palm, Phoenix dactylifera
- Chusan Palm, Trachycarpus fortunei
- Poaceae (grass family)
- Bamboos Poaceae subfamily Bambusoideae
- Note that banana 'trees' are not actually trees; they are not woody nor is the stalk perennial.

Conifers (Pinophyta; softwood trees)

- Araucariaceae (Araucaria family)
- Araucaria, Araucaria species
- Kauri, Agathis species
- Cupressaceae (Cypress family)
- Cypress, Cupressus species
- Cypress, Chamaecyparis species
- Juniper, Juniperus species
- Alerce or Patagonian cypress, Fitzroya cupressoides
- Sugi, Cryptomeria japonica
- Coast Redwood, Sequoia sempervirens
- Giant Sequoia, Sequoiadendron giganteum
- Dawn Redwood, Metasequoia glyptostroboides
- Bald Cypress, Taxodium distichum
- Pinaceae (Pine family)
- White pine, Pinus species
- Pinyon pine, Pinus species
- Pine, Pinus species
- Spruce, Picea species
- Larch, Larix species
- Douglas-fir, Pseudotsuga species
- Fir, Abies species
- Cedar, Cedrus species
- Podocarpaceae (Yellowwood family)
- African Yellowwood, Afrocarpus falcatus
- Totara, Podocarpus totara
- Sciadopityaceae
- Kusamaki, Sciadopitys species
- Taxaceae (Yew family)
- Yew, Taxus species

Ginkgos (Ginkgophyta)

- Ginkgoaceae (Ginkgo family)
- Ginkgo, Ginkgo biloba

Cycads (Cycadophyta)

- Cycadaceae family
- Ngathu cycad, Cycas angulata
- Zamiaceae family
- Wunu cycad, Lepidozamia hopei

Ferns (Pterophyta)

- Cyatheaceae and Dicksoniaceae families
- Tree ferns, Cyathea, Alsophila, Dicksonia (not a monophyletic group)

Life stages

The life cycles of trees, especially conifers, are divided into the following stages in forestry for survey and documentation purposes: # Seed # Seedling: the above ground part of the embryo that sprout from the seed # Sapling: After the seedling reaches 1m tall, and until it reaches 7cm in stem diameter # Pole: young trees from 7-30cm diameter # Mature tree: over 30cm diameter, reproductive years begin # Old tree: dominate old growth forest; height growth slows greatly, with majority of productivity in seed production # Overmature: dieback and decay become common # Snag: standing dead wood # Log/debris: fallen dead wood Tree diameters are measured at height of between 1.3-1.5m above the highest point on the ground at its base. The 7cm diameter definition is economically based, from the smallest saleable stem size (for paper production, etc), and the 30cm diameter is the smallest base diameter for sawlogs. Each stage may be uniquely perceptive to different pathogens and suitable for especially adapted arboreal animals.

External links

- [http://www.globaltrees.org/default.asp GLOBAL TREES .org] Campaigning to save the world's most threatened trees
- [http://www.fssca.net/romero/ Romero Memorial Tree Project] Plant a tree in El Salvador

Bibliography

- Pakenham, T. (2002). Remarkable Trees of the World. ISBN 0297843001
- Pakenham, T. (1996). Meetings with Remarkable Trees. ISBN 0297832557 Category:Plants
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- Category:Botany Category: plant morphology ms:Pokok ja:木 simple:Tree th:ต้นไม้

Fruit

In botany, a fruit is the ripened ovary—together with seeds—of a flowering plant. In many species, the fruit incorporates the ripened ovary and surrounding tissues. Fruits are the means by which flowering plants disseminate seeds. Evolution has led plants to adopt certain basic mechanisms, seemingly without close regard to the tissues involved. No one terminology really fits the enormous variety that is found among plant fruits. Botanical terminology for fruits is inexact and will remain so. In cuisine, when discussing fruit as food, the term usually refers to just those plant fruits that are sweet and fleshy, examples of which include plum, apple and orange. However, a great many common vegetables, as well as nuts and grains, are the fruit of the plant species they come from. The term false fruit (pseudocarp, accessory fruit) is sometimes applied to a fruit like the fig (a multiple-accessory fruit; see below) or to a plant structure that resembles a fruit but is not derived from a flower or flowers. Some gymnosperms, such as yew, have fleshy arils that resemble fruits and some junipers have berry-like, fleshy cones. With most fruits pollination is a vital part of fruit culture, and the lack of knowledge of pollinators and pollenizers can contribute to poor crops or poor quality crops. In a few species, the fruit may develop in the absence of pollination/fertilization, a process known as parthenocarpy. Such fruits are seedless. A plant that does not produce fruit is known as acarpous, meaning essentially "without fruit".

Botanic fruits and culinary fruits

Many foods are botanically a fruit, but are treated as vegetables in cooking. These include cucurbits (e.g. squash and pumpkin), maize, tomatoes, cucumber, aubergines (eggplants) and green peppers, along with nuts, and some spices, such as allspice, nutmeg and chiles. Rarely, culinary "fruits" are not fruits in the botanical sense. For example, rhubarb may be considered a fruit, though only the astringent stalk, or petiole, is edible. In the commercial world, European Union rules define carrot as a fruit for the purposes of measuring the proportion of "fruit" contained in carrot jam.

Fruit development

After an ovule is fertilized in a process known as pollination, the ovary begins to expand. The petals of the flower fall off and the ovule develops into a seed. The ovary eventually comes to form, along with other parts of the flower in many cases, a structure surrounding the seed or seeds that is the fruit. Fruit development continues until the seeds have matured. With some multiseeded fruits the extent of development of the flesh of the fruit is proportional to the number of fertilized ovules. The wall of the fruit, developed from the ovary wall of the flower, is called the pericarp. The pericarp is often differentiated into two or three distinct layers called the exocarp (outer layer - also called epicarp), mesocarp (middle layer), and endocarp (inner layer). In some fruits, especially simple fruits derived from an inferior ovary, other parts of the flower (such as the floral tube, including the petals, sepals, and stamens), fuse with the ovary and ripen with it. When such other floral parts are a significant part of the fruit, it is called an accessory fruit. Since other parts of the flower may contribute to the structure of the fruit, it is important to study flower structure to understand how a particular fruit forms. Fruits are so varied in form and development, that it is difficult to devise a classification scheme that includes all known fruits. It will also be seen that many common terms for seeds and fruit are incorrectly applied, a fact that complicates understanding of the terminology. Seeds are ripened ovules; fruits are the ripened ovularies or carpels that contain the seeds. To these two basic definitions can be added the clarification that in botanical terminology, a nut is a type of fruit and not another term for seed. There are three basic types of fruits: # Simple fruit # Aggregate fruit # Multiple fruit

Simple fruit

Simple fruits can be either dry or fleshy and result from the ripening of a simple or compound ovary with only one pistil. Dry fruits may be either dehiscent (opening to discharge seeds), or indehiscent (not opening to discharge seeds). Types of dry, simple fruits (with examples) are:
- achene - (buttercup)
- capsule - (Brazil nut)
- caryopsis - (wheat)
- fibrous drupe - (coconut, walnut)
- follicle - (milkweed)
- legume - (pea, bean, peanut)
- loment
- nut - (hazelnut, beech, oak acorn)
- samara - (elm, ash, maple key)
- schizocarp - (carrot)
- silique - (radish)
- utricle Fruits in which part or all of the pericarp (fruit wall) is fleshy at maturity are simple fleshy fruits. Types of fleshy, simple fruits (with examples) are:
- berry - (tomato, avocado)
- drupe - (plum, cherry, peach, olive)
- false berry - accessory fruits (banana, cranberry)
- pome - accessory fruits (apple, pear, rosehip)

Aggregate fruit

rosehip An aggregate fruit, or etaerio, develops from a flower with numerous simple pistils. An example is the raspberry, whose simple fruits are termed drupelets because each is like a small drupe attached to the receptacle. In some bramble fruits (such as blackberry) the receptacle is elongate and part of the ripe fruit, making the blackberry an aggregate-accessory fruit. The strawberry is also an aggregate-accessory fruit, only one in which the seeds are contained in achenes. In all these examples, the fruit develops from a single flower with numerous pistils.

Multiple fruit

A multiple fruit is one formed from a cluster of flowers (called an inflorescence). Each flower produces a fruit, but these mature into a single mass. Examples are the pineapple, edible fig, mulberry, osage-orange, and breadfruit. breadfruit In the photograph on the right, stages of flowering and fruit development in the noni or Indian mulberry (Morinda citrifolia) can be observed on a single branch. First an inflorescence of white flowers called a head is produced. After fertilization, each flower develops into a drupe, and as the drupes expand, they connate (merge) into a multiple fleshy fruit called a syncarp.

Seedless Fruits

Seedlessness is an important feature of some fruits of commerce. Commercial cultivars of bananas and pineapples are seedless. Some cultivars of citrus fruits (especially navel oranges and mandarin oranges), table grapes, grapefruit, and watermelons are valued for their seedlessness. In some species, seedlessness is the result of parthenocarpy, where fruits set without fertilization. Parthenocarpic fruit set may or may not require pollination. Most seedless citrus fruits require a pollination stimulus; bananas and pineapples do not. Seedlessness in table grapes results from the abortion of the embryonic plant that is produced by fertilization, a phenomenon known as stenospermocarpy which requires normal pollination and fertilization.

Seed dissemination

Variations in fruit structures largely relate to dissemination (called dispersal) of the seeds they contain. Some fruits have coats covered with spikes or hooked burrs, either to prevent themselves from being eaten by animals or to stick to the hairs of animals, using them as dispersal agents. Other fruits are elongated and flattened out naturally and so become thin, like wings or helicopter blades. This is an evolutionary mechanism to increase dispersal distance away from the parent.

Uses

Many fruits, including fleshy fruits like apple and mango, and nuts like walnut, are commercially valuable as human food, eaten both fresh and made into jams, marmalade and other preserves for future consumption. Fruits are also found commonly in such manufactured foods as cookies, muffins, yoghurt, ice cream, cakes, and many more.

Seed

A seed is the ripened ovule of gymnosperm or angiosperm plants. The importance of the seed relative to more primitive forms of reproduction and dispersal is attested to by the success of these two groups of plants in dominating the landscape.

Seed structure

A fertilized seed contains the embryo from which a new plant will grow under proper conditions. It also contains a supply of stored food and is wrapped in the seed coat or testa. The stored food begins as a tissue called endosperm derived from the parent plant. Endosperm becomes rich in oil or starch, and protein. In some species, the embryo is imbedded in the endosperm, which the seedling will use upon germination. In others, the endosperm is absorbed by the embryo as the latter grows within the developing seed, and the cotyledons of the embryo become filled with this stored food. At maturity, seeds of these species have no endosperm. Some common plant seeds that lack an endosperm are bean, pea, oak, walnut, squash, sunflower, and radish. Plant seeds with an endosperm include all conifers and most monocotyledons (e.g. grasses and palms), and also e.g. brazil nut, castor bean. castor bean See also: Hypocotyl The seed coat develops from tissues (called integument) originally surrounding the ovule. The seed coat in the mature seed can be a paper thin layer (as for example, in the peanut) or something more substantial (as for example, thick and hard in honey locust and coconut). The seed coat helps protect the embryo from mechanical injury and from drying out. In order for the seed coat to split, the embryo must imbibe (soak up water) which causes it to swell, splitting the seed coat. However, the nature of the seed coat determines how rapidly water can penetrate and subsequently initiate germination. For seeds with a very thick coat, scarification of the seed coat may be necessary before water can reach the embryo. Examples of scarification include: gnawing by animals, freezing and thawing, battering on rocks in a stream bed, or passing through an animal's digestive tract. In the latter case, the seed coat protects the seed from digestion, while perhaps weakening the seed coat such that the embryo is ready to sprout when it gets deposited (along with a bit of fertilizer) far from the parent plant. In species with thin seed coats, light may be able to penetrate into the dormant embryo. The presence of light or the absence of light may trigger the germination process, inhibiting germination in some seeds buried too deeply or in others not buried in the soil. Abscisic acid is usually the growth inhibitor in seeds. The seeds of angiosperms are contained in a hard or fleshy (or with layers of both) structure called a fruit. Gymnosperm seeds begin their development "naked" on the bracts of cones, although the seeds do become covered by the cone scales as they develop. An example of a hard fruit layer surrounding the actual seed is that of the so-called stone fruits (such as the peach).

Seed functions

Unlike animals, plants are limited in their ability to seek out favorable conditions for life and growth. Consequently, plants have evolved many ways to disperse and spread the population through their seeds (see also vegetative reproduction). A seed must somehow "arrive" at a location and be there at a time favorable for germination and growth. Those properties or attributes that promote the movement of the next generation away from the parent plant may involve the fruit more so than the seeds themselves. The function of a seed typically is one of serving as a delaying mechanism: a way for the new generation to suspend its growth and allow time for dispersal to occur or to survive harsh, unfavorable conditions of cold or dryness or both. In many if not most cases each plant species achieves success in finding ideal locations for placement of its seeds through the basic approach of producing numerous seeds. This is certainly the approach used by plants, such as ferns, that disperse by spores. However, seeds involve a considerably greater investment in energy and resources than do spores, and the payoff must come in achieving similar or greater success with fewer dispersal units.

External links

- [http://www.seedlab.co.nz/NAMESEED.HTM List of Common Botanical Seed Names]
- [http://theseedsite.co.uk/ The Seed Site]: collecting, storing, sowing, germinating, and exchanging seeds, with pictures of seeds, seedpods and seedlings. Category:Plants Category: plant morphology Category:Vegetables Category:Flowers ko:씨 ja:種子 simple:Seed

Fructose

Fructose is a simple sugar (monosaccharide) found in many foods and one of the three most important blood sugars along with glucose and galactose. Honey; tree fruits; berries; melons; and some root vegetables, such as beets, sweet potatoes, parsnips and onions, contain fructose, usually in combination with sucrose and glucose. Fructose is also derived from the digestion of sucrose, a disaccharide consisting of glucose and fructose that is broken down by enzymes during digestion. Fructose is often recommended for, and consumed by, people with diabetes mellitus or hypoglycemia, because it has a very low Glycemic Index (GI 32) relative to cane sugar (sucrose). The low GI is due to the unique and lengthy metabolic pathway of fructose, which involves phosphorylation and a multi-step enzymatic process in the liver. See health effects and glycation for further informations.

Structure

image:d-fructose.png
Structure formula of fructose

Fructose, or levulose, is a levorotatory monosaccharide with the same empirical formula as glucose (C₆H₁₂O₆) but with a different structure. Although fructose is a hexose (6 carbon sugar), it generally exists as a 5-member hemiketal ring (a furanose). The first -OH points the opposite way from the second and third -OH.

Isomerism

D-Fructose has the same configuration at its penultimate carbon as D-glyceraldehyde. Fructose is sweeter than glucose due to its stereomerism structure Image:Alpha-D-Fructose-structure-corrected.png|alpha-D-Fructose Image:Beta-D-Fructose-structure.png|beta-D-Fructose Image:Alpha-L-Fructose-structure-corrected.png|alpha-L-Fructose Image:Beta-L-Fructose-structure.png|beta-L-Fructose

Health effects

Fructose depends on glucose to carry it into the blood stream via GLUT-5 and then GLUT-2 (Buchs et al 1998). Absorption of fructose without glucose present is very poor, and excess fructose is carried into the lower intestine where it provides nutrients for the existing flora, which produce gas. It may also cause water retention in the intestine. These effects may lead to bloating, excessive flatulence, loose stools, and even diarrhea depending on the amounts eaten and other factors. Fructose has by some been hypothesized to cause obesity (Elliott et al 2002), elevated LDL cholesterol and triglycerides, leading to metabolic syndrome. Supplementation with fructose in the diet in human subjects has however not lead to increased obesity. Fructose also chelates minerals in the blood. This effect is especially important with micronutrients such as copper, chromium and zinc. Since these solutes are normally present in small quantities, chelation of small numbers of ions may lead to deficiency diseases, immune system impairment and even insulin resistance, a component of type II diabetes (Higdon). Fructose is a reducing sugar, as are all monosaccharides. However, it is considered approximately ten times more active (McPherson et al 1988) in the formation of glycations than glucose, so consumption should be limited in order to limit the consequent glycation-related damage to cellular and molecular function. This may be an important contribution to senescence and many age-related chronic diseases (Levi & Werman 1998).

References

- Buchs AE, Sasson S, Joost HG, Cerasi E. Characterization of GLUT5 domains responsible for fructose transp