Flowering plant
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any
Wheat
Wheat is a grass cultivated for its seed, a cereal grain, a worldwide staple food. The many species of wheat together make up the genus Triticum; the archaeological record suggests that wheat was first cultivated in the regions of the Fertile Crescent around 9600 BCE. Botanically, the wheat kernel is a type of fruit called a caryopsis. Wheat is grown on more land area than any other food crop. World trade in wheat is greater than for all other crops combined. In 2016, world production of wheat was 749 million tonnes, making it the second most-produced cereal after maize. Since 1960, world production of wheat and other grain crops has tripled and is expected to grow further through the middle of the 21st century. Global demand for wheat is increasing due to the unique viscoelastic and adhesive properties of gluten proteins, which facilitate the production of processed foods, whose consumption is increasing as a result of the worldwide industrialization process and the westernization of the diet.
Wheat is an important source of carbohydrates. Globally, it is the leading source of vegetal protein in human food, having a protein content of about 13%, high compared to other major cereals but low in protein quality for supplying essential amino acids; when eaten as the whole grain, wheat is a source of dietary fiber. In a small part of the general population, gluten – the major part of wheat protein – can trigger coeliac disease, noncoeliac gluten sensitivity, gluten ataxia, dermatitis herpetiformis. Cultivation and repeated harvesting and sowing of the grains of wild grasses led to the creation of domestic strains, as mutant forms of wheat were preferentially chosen by farmers. In domesticated wheat, grains are larger, the seeds remain attached to the ear by a toughened rachis during harvesting. In wild strains, a more fragile rachis allows the ear to shatter and disperse the spikelets. Selection for these traits by farmers might not have been deliberately intended, but have occurred because these traits made gathering the seeds easier.
As the traits that improve wheat as a food source involve the loss of the plant's natural seed dispersal mechanisms domesticated strains of wheat cannot survive in the wild. Cultivation of wheat began to spread beyond the Fertile Crescent after about 8000 BCE. Jared Diamond traces the spread of cultivated emmer wheat starting in the Fertile Crescent sometime before 8800 BCE. Archaeological analysis of wild emmer indicates that it was first cultivated in the southern Levant, with finds dating back as far as 9600 BCE. Genetic analysis of wild einkorn wheat suggests that it was first grown in the Karacadag Mountains in southeastern Turkey. Dated archeological remains of einkorn wheat in settlement sites near this region, including those at Abu Hureyra in Syria, suggest the domestication of einkorn near the Karacadag Mountain Range. With the anomalous exception of two grains from Iraq ed-Dubb, the earliest carbon-14 date for einkorn wheat remains at Abu Hureyra is 7800 to 7500 years BCE. Remains of harvested emmer from several sites near the Karacadag Range have been dated to between 8600 and 8400 BCE, that is, in the Neolithic period.
With the exception of Iraq ed-Dubb, the earliest carbon-14 dated remains of domesticated emmer wheat were found in the earliest levels of Tell Aswad, in the Damascus basin, near Mount Hermon in Syria. These remains were dated by Willem van Zeist and his assistant Johanna Bakker-Heeres to 8800 BCE, they concluded that the settlers of Tell Aswad did not develop this form of emmer themselves, but brought the domesticated grains with them from an as yet unidentified location elsewhere. The cultivation of emmer reached Greece and Indian subcontinent by 6500 BCE, Egypt shortly after 6000 BCE, Germany and Spain by 5000 BCE. "The early Egyptians were developers of bread and the use of the oven and developed baking into one of the first large-scale food production industries." By 3000 BCE, wheat had reached Scandinavia. A millennium it reached China; the oldest evidence for hexaploid wheat has been confirmed through DNA analysis of wheat seeds, dating to around 6400-6200 BCE, recovered from Çatalhöyük.
The first identifiable bread wheat with sufficient gluten for yeasted breads has been identified using DNA analysis in samples from a granary dating to 1350 BCE at Assiros in Macedonia. From Asia, wheat continued to spread across Europe. In the British Isles, wheat straw was used for roofing in the Bronze Age, was in common use until the late 19th century. Technological advances in soil preparation and seed placement at planting time, use of crop rotation and fertilizers to improve plant growth, advances in harvesting methods have all combined to promote wheat as a viable crop; when the use of seed drills replaced broadcasting sowing of seed in the 18th century, another great increase in productivity occurred. Yields of pure wheat per unit area increased as methods of crop rotation were applied to long cultivated land, the use of fertilizers became widespread. Improved agricultural husbandry has more included threshing machines and reaping machines, tractor-drawn cultivators and planters, better varieties.
Great expansion of wheat production occurred as new arable land was farmed in the Americas and Australia in the 19th and 20th centuries. Leaves emerge from the shoot apical meristem in a telescoping fashion until the transition to reprod
Radiocarbon dating
Radiocarbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was developed in the late 1940s by Willard Libby, who received the Nobel Prize in Chemistry for his work in 1960, it is based on the fact that radiocarbon is being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14C combines with atmospheric oxygen to form radioactive carbon dioxide, incorporated into plants by photosynthesis; when the animal or plant dies, it stops exchanging carbon with its environment, from that point onwards the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay. Measuring the amount of 14C in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died; the older a sample is, the less 14C there is to be detected, because the half-life of 14C is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods permit accurate analysis of older samples.
Research has been ongoing since the 1960s to determine what the proportion of 14C in the atmosphere has been over the past fifty thousand years. The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age. Other corrections must be made to account for the proportion of 14C in different types of organisms, the varying levels of 14C throughout the biosphere. Additional complications come from the burning of fossil fuels such as coal and oil, from the above-ground nuclear tests done in the 1950s and 1960s; because the time it takes to convert biological materials to fossil fuels is longer than the time it takes for its 14C to decay below detectable levels, fossil fuels contain no 14C, as a result there was a noticeable drop in the proportion of 14C in the atmosphere beginning in the late 19th century. Conversely, nuclear testing increased the amount of 14C in the atmosphere, which attained a maximum in about 1965 of twice what it had been before the testing began.
Measurement of radiocarbon was done by beta-counting devices, which counted the amount of beta radiation emitted by decaying 14C atoms in a sample. More accelerator mass spectrometry has become the method of choice; the development of radiocarbon dating has had a profound impact on archaeology. In addition to permitting more accurate dating within archaeological sites than previous methods, it allows comparison of dates of events across great distances. Histories of archaeology refer to its impact as the "radiocarbon revolution". Radiocarbon dating has allowed key transitions in prehistory to be dated, such as the end of the last ice age, the beginning of the Neolithic and Bronze Age in different regions. In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research, they synthesized 14C using the laboratory's cyclotron accelerator and soon discovered that the atom's half-life was far longer than had been thought.
This was followed by a prediction by Serge A. Korff employed at the Franklin Institute in Philadelphia, that the interaction of thermal neutrons with 14N in the upper atmosphere would create 14C, it had been thought that 14C would be more to be created by deuterons interacting with 13C. At some time during World War II, Willard Libby, at Berkeley, learned of Korff's research and conceived the idea that it might be possible to use radiocarbon for dating. In 1945, Libby moved to the University of Chicago, he published a paper in 1946 in which he proposed that the carbon in living matter might include 14C as well as non-radioactive carbon. Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, after isotopically enriching their samples they were able to demonstrate that they contained 14C. By contrast, methane created from petroleum showed no radiocarbon activity because of its age; the results were summarized in a paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin.
Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages. For example, two samples taken from the tombs of two Egyptian kings and Sneferu, independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus or minus 250 years; these results were published in Science in 1949. Within 11 years of their announcement, more than 20 radiocarbon dating laboratories had been set up worldwide. In 1960, Libby was awarded the Nobel Prize in Chemistry for this work. In nature, carbon exists as two stable, nonradioactive isotopes: carbon-12, carbon-13, a radioactive isotope, carbon-14 known as "radiocarbon"; the half-life
Poales
The Poales are a large order of flowering plants in the monocotyledons, includes families of plants such as the grasses and sedges. Sixteen plant families are recognized by botanists to be part of Poales; the flowers are small, enclosed by bracts, arranged in inflorescences. The flowers of many species are wind pollinated; the APG III system accepts the order within a monocot clade called commelinids, accepts the following 16 families: The earlier APG system adopted the same placement of the order, although it used the spelling "commelinoids". It did not include the Bromeliaceae and Mayaceae, but had the additional families Prioniaceae and Hydatellaceae; the morphology-based Cronquist system did not include an order named Poales, assigning these families to the orders Bromeliales, Hydatellales, Juncales and Typhales. In early systems, an order including the grass family did not go by the name Poales but by a descriptive botanical name such as Graminales in the Engler system and in the Hutchinson system, Glumiflorae in the Wettstein system or Glumaceae in the Bentham & Hooker system.
The earliest fossils attributed to the Poales date to the late Cretaceous period about 66 million years ago, though some studies suggest the origin of the group may extend to nearly 115 million years ago in South America. The earliest known fossils include pollen and fruits; the phylogenetic position of Poales within the commelinids was difficult to resolve, but an analysis using complete chloroplast DNA found support for Poales as sister group of Commelinales plus Zingiberales. Major lineages within the Poales have been referred to as bromeliad, xyrid and restiid clades. A phylogenetic analysis resolved most relationships within the order but found weak support for the monophyly of the cyperid clade; the relationship between Centrolepidaceae and Restoniaceae within the restiid clade remains unclear. The four most species-rich families in the order are: Poaceae: 12,070 species Cyperaceae: 5,500 species Bromeliaceae: 3,170 species Eriocaulaceae: 1,150 speciesDiversity of Poales The Poales are the most economically important order of monocots and the most important order of plants in general.
Within the order, by far the most important family economically is the family of grasses, which includes the starch staples barley, millet and wheat as well as bamboos, a few "seasonings" like sugarcane and lemongrass. Graminoids the grasses, are dominant in open habitats like prairie/steppe and savannah and thus form a large proportion of the forage of grazing livestock. Due to pastoral nostalgia or a desire for open areas for play, they dominate most Western yards as lawns, which consume vast sums of money in upkeep. Many Bromeliaceae are used as ornamental plants. Many wetland species of sedges, rushes and cattails are important habitat plants for waterfowl, are used in weaving chair seats, were important pre-agricultural food sources for man. Two sedges and water chestnut are still at least locally important wetland starchy root crops. Bremer, K. "Gondwanan Evolution of the Grass Alliance of Families". Evolution. 56: 1374–1387. Doi:10.1111/j.0014-3820.2002.tb01451.x. Judd, W. S. C. S. Campbell, E. A. Kellogg, P. F. Stevens, M. J. Donoghue.
Plant Systematics: A Phylogenetic Approach, 2nd edition. Pp. 276–292. Sinauer Associates, Massachusetts. ISBN 0-87893-403-0. Linder, H. Peter. "Evolutionary History of the Poales". Annual Review of Ecology and Systematics. 36: 107–124. Doi:10.1146/annurev.ecolsys.36.102403.135635. Small, J. K.. Flora of the Southeastern United States, 48. New York, United States NCBI Taxonomy Browser APWeb
Jericho
Jericho is a city in the Palestinian Territories and is located near the Jordan River in the West Bank. It is the administrative seat of the Jericho Governorate, is governed by the Fatah faction of the Palestinian National Authority. In 2007, it had a population of 18,346; the city was occupied by Jordan from 1949 to 1967, has been held under Israeli occupation since 1967. It is believed to be one of the oldest inhabited cities in the world and the city with the oldest known protective wall in the world, it was thought to have the oldest stone tower in the world as well, but excavations at Tell Qaramel in Syria have discovered stone towers that are older. Archaeologists have unearthed the remains of more than 20 successive settlements in Jericho, the first of which dates back 11,000 years to the beginning of the Holocene epoch of the Earth's history. Copious springs in and around the city have attracted human habitation for thousands of years. Jericho is described in the Hebrew Bible as the "city of palm trees".
Jericho's name in Hebrew, Yeriẖo, is thought to derive from the Canaanite word reaẖ, but other theories hold that it originates in the Canaanite word for "moon" or the name of the lunar deity Yarikh for whom the city was an early centre of worship. Jericho's Arabic name, ʼArīḥā, means "fragrant" and has its roots in Canaanite Reaẖ; the first excavations of the site were made by Charles Warren in 1868. Ernst Sellin and Carl Watzinger excavated Tell es-Sultan and Tulul Abu el-'Alayiq between 1907 and 1909, in 1911, John Garstang excavated between 1930 and 1936. Extensive investigations using more modern techniques were made by Kathleen Kenyon between 1952 and 1958. Lorenzo Nigro and Nicolò Marchetti conducted excavations in 1997–2000. Since 2009 the Italian-Palestinian archaeological project of excavation and restoration was resumed by Rome "La Sapienza" University and Palestinian MOTA-DACH under the direction of Lorenzo Nigro and Hamdan Taha, Jehad Yasine since 2015; the Italian-Palestinian Expedition carried out 13 seasons in 20 years, with some major discoveries, like Tower A1 in the Middle Bronze Age southern Lower Town and Palace G on the eastern flanks of the Spring Hill overlooking the Spring of'Ain es-Sultan dating from Early Bronze III.
The earliest settlement was located at the present-day Tell es-Sultan, a couple of kilometers from the current city. In both Arabic and Hebrew, tell means "mound" – consecutive layers of habitation built up a mound over time, as is common for ancient settlements in the Middle East and Anatolia. Jericho is the type site for the Pre-Pottery Neolithic Pre-Pottery Neolithic B periods. Epipaleolithic construction at the site appears to predate the invention of agriculture, with the construction of Natufian culture structures beginning earlier than 9000 BCE, the beginning of the Holocene epoch in geologic history. Jericho has evidence of settlement dating back to 10,000 BCE. During the Younger Dryas period of cold and drought, permanent habitation of any one location was impossible. However, the Ein es-Sultan spring at what would become Jericho was a popular camping ground for Natufian hunter-gatherer groups, who left a scattering of crescent-shaped microlith tools behind them. Around 9600 BCE, the droughts and cold of the Younger Dryas stadial had come to an end, making it possible for Natufian groups to extend the duration of their stay leading to year-round habitation and permanent settlement.
The first permanent settlement on the site of Jericho developed near the Ein es-Sultan spring between 9,500 and 9000 BCE. As the world warmed up, a new culture based on agriculture and sedentary dwelling emerged, which archaeologists have termed "Pre-Pottery Neolithic A", its cultures lacked pottery, but featured the following: small circular dwellings burial of the dead under the floor of buildings reliance on hunting of wild game cultivation of wild or domestic cerealsAt Jericho, circular dwellings were built of clay and straw bricks left to dry in the sun, which were plastered together with a mud mortar. Each house measured about 5 metres across, was roofed with mud-smeared brush. Hearths were located outside the homes. By about 9400 BCE, the town had grown to more than 70 modest dwellings; the Pre-Sultan is sometimes called Sultanian. The site is a 40,000 square metres settlement surrounded by a massive stone wall over 3.6 metres high and 1.8 metres wide at the base, inside of which stood a stone tower, over 8.5 metres high, containing an internal staircase with 22 stone steps and placed in the centre of the west side of the tell.
This tower and the older ones excavated at Tell Qaramel in Syria are the oldest to be discovered. The wall may have served as a defence against flood-water, with the tower used for ceremonial purposes; the wall and tower were built during the Pre-Pottery Neolithic A period around 8000 BCE. For the tower, carbon dates published in 1981 and 1983 indicate that it was built around 8300 BCE and stayed in use until c. 7800 BCE. The wall and tower would have taken a hundred men more than a hundred days to construct, thus suggesting some kind of social organization; the town contained round mud-brick houses, yet no street planning. The identity and number of the inhabitants of Jericho during the PPNA period is still under debate, with estimates going as high as 2,000–3,000, as low as 200–300, it is known that this population had domesticated emmer whea
Aegilops
Aegilops is a genus of Eurasian and North American plants in the grass family, Poaceae. They are known as goatgrasses; some species are known as invasive weeds in parts of North America. These are annual plants, sometimes from rhizomes; the taller species reach about 80 centimeters in maximum height. The flat leaves are linear to narrowly lance-shaped, are up to 15 centimeters long and one wide; the inflorescence is a spike with 2 to 12 solitary spikelets each up to 1.2 centimeters long. Some spikelets have one or three awns, some have none. Genus Aegilops has played an important role in the taxonomy of wheat; the familiar common wheat arose when cultivated emmer wheat hybridized with Aegilops tauschii about 8,000 years ago. Aegilops and Triticum are genetically similar, as evidenced by their ability to hybridize, by the presence of Aegilops in the evolutionary heritage of many Triticum taxa. Aegilops is sometimes treated within Triticum, they are maintained as separate genera by most authorities because of their ecological characteristics, because when united they do not form a monophyletic group.
Some Aegilops are known as weeds. A. cylindrica, known as jointed goatgrass, infests wheat fields, where it outcompetes wheat plants, reducing yields. Its seeds mix with wheat grains at harvest, lowering the quality of the crop, it can harbor pests such as the Russian wheat aphid and pathogenic fungi. Other Aegilops are weeds of wildland habitat. During the Mesolithic era, nomadic peoples found goatgrasses growing wild, along with wild wheats and barleys, harvested them using bone sickles inset with sharp flakes of flint; the harvested plants were left to dry for a few days the edible grains were separated out from the rest of the plant material by beating the plants with a wooden flail, or by rolling them against a hard surface. The seeds were carefully singed in the embers of a fire to burn away the remaining non-edible plant material; some grains were accidentally burnt, since the burnt grains do not biodegrade some have been found by modern archeologists. The genus name Aegilops comes from the Greek aegilos, which could mean "a goat", "goatlike", "a herb liked by goats", or "a grass similar to that liked by goats".
The word "Aegilops" is claimed to be the longest word in the English language to have all of its letters in alphabetical order. Accepted SpeciesAegilops bicornis - Egypt, Cyprus, Syria, Sinai, Israel Kuwait Aegilops biuncialis - Mediterranean Basin, Ukrain, Caucasus Aegilops caudata - Balkans, Middle East Aegilops columnaris - Middle East Aegilops comosa - Greece, Turkey Aegilops crassa – Persian goatgrass - Middle East to Central Asia Aegilops cylindrica – jointed goatgrass - from Czech Republic to Pakistan Aegilops geniculata - from Portugal + Canary Islands to Iran Aegilops × insulae-cypri - Cyprus Aegilops juvenalis - from Turkey to Kazakhstan Aegilops kotschyi – ovate goatgrass - from Tunisia to Uzbekistan Aegilops longissima - Middle East, Egypt Aegilops lorentii - from Spain + Cape Verde to Iran Aegilops mutica - Turkey, Transcaucasus Aegilops neglecta – three-awned goatgrass - from Portugal + Canary Islands to Kazakhstan Aegilops peregrina - from Morocco to Iran Aegilops searsii - Syria, Jordan Aegilops sharonensis - Israel Aegilops speltoides - from Greece to Iran Aegilops tauschii - from Crimea to Henan Aegilops triuncialis – barbed goatgrass - from Portugal + Morocco to Kazakhstan Aegilops umbellulata - from Crimea to Iran Aegilops uniaristata - Italy, Turkey, Caucasus Aegilops vavilovii - from Caucasus to Saudi Arabia Aegilops ventricosa - from Morocco + Balearic Islands to CaucasusFormerly included speciesSpecies once regarded as members of Aegilops but now considered better suited to other genera: Ctenium, Elymus, Ophiuros, Parapholis and Triticum List of Poaceae genera Media related to Aegilops at Wikimedia Commons
Media related to Triticum dicoccum at Wikimedia Commons
