The stigma is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma, together with the style and ovary comprises the pistil, which in turn is part of the gynoecium or female reproductive organ of a plant; the stigma forms the distal portion of the stylodia. The stigma is composed of the cells which are receptive to pollen; these may be restricted to the apex of the style or in wind pollinated species, cover a wide surface. The stigma receives pollen and it is on the stigma that the pollen grain germinates. Sticky, the stigma is adapted in various ways to catch and trap pollen with various hairs, flaps, or sculpturings; the pollen may be captured from the air, from visiting insects or other animals, or in rare cases from surrounding water. Stigma can slender to globe shaped to feathery. Pollen is highly desiccated when it leaves an anther. Stigma have been shown to assist in the rehydration of pollen and in promoting germination of the pollen tube. Stigma ensure proper adhesion of the correct species of pollen.
Stigma can play an active role in pollen discrimination and some self-incompatibility reactions, that reject pollen from the same or genetically similar plants, involve interaction between the stigma and the surface of the pollen grain. The stigma is split into lobes, e.g. trifid, may resemble the head of a pin, or come to a point. The shape of the stigma may vary considerably: The style is a narrow upward extension of the ovary, connecting it to the stigmatic papillae, it may be absent in some plants in the case. Styles are tube-like—either long or short; the style can be open with a central canal. Alternatively the style may be closed. Most syncarpous monocots and some eudicots have open styles, while many syncarpous eudicots and grasses have closed styles containing specialised secretory transmitting tissue, linking the stigma to the centre of the ovary; this forms a nutrient rich tract for pollen tube growth. Where there are more than one carpel to the pistil, each may have a separate style-like stylodium, or share a common style.
In Irises and others in the Iridaceae family, the style divides into three petal-like style branches to the base of the style and is called tribrachiate. These are flaps of tissue, running from the perianth tube above the sepal; the stigma is a edge on the underside of the branch, near the end lobes. Style branches appear on Dietes and most species of Moraea. In Crocuses, there are three divided style branches. Hesperantha has a spreading style branch. Alternatively the style may be lobed rather than branched. Gladiolus has a bi-lobed style branch. Freesia, Romulea and Watsonia have bifuracated and recurved style branches. May be terminal, lateral, gynobasic, or subgynobasic. Terminal style position is the commonest pattern. In the subapical pattern the style arises to the side below the apex. A lateral style is found in Rosaceae; the gynobasic style arises from the base of the ovary, or between the ovary lobes and is characteristic of Boraginaceae. Subgynobasic styles characterise Allium. Pollen tubes grow the length of the style to reach the ovules, in some cases self-incompatibility reactions in the style prevent full growth of the pollen tubes.
In some species, including Gasteria at least, the pollen tube is directed to the micropyle of the ovule by the style. Gynoecium Stigma shape and size - English labels Terminal versus gynobasic style Images Gynobasic Diagram
Ecuador the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, the Pacific Ocean to the west. Ecuador includes the Galápagos Islands in the Pacific, about 1,000 kilometres west of the mainland; the capital city is Quito, the largest city. What is now Ecuador was home to a variety of Amerindian groups that were incorporated into the Inca Empire during the 15th century; the territory was colonized by Spain during the 16th century, achieving independence in 1820 as part of Gran Colombia, from which it emerged as its own sovereign state in 1830. The legacy of both empires is reflected in Ecuador's ethnically diverse population, with most of its 16.4 million people being mestizos, followed by large minorities of European and African descendants. Spanish is the official language and is spoken by a majority of the population, though 13 Amerindian languages are recognized, including Quichua and Shuar; the sovereign state of Ecuador is a middle-income representative democratic republic with a developing economy, dependent on commodities, namely petroleum and agricultural products.
It is governed as a democratic presidential republic. One of 18 megadiverse countries in the world, Ecuador hosts many endemic plants and animals, such as those of the Galápagos Islands. In recognition of its unique ecological heritage, the new constitution of 2008 is the first in the world to recognize enforceable Rights of Nature, or ecosystem rights, it has the fifth lowest homicide rate in the Americas. Various peoples had settled in the area of the future Ecuador before the arrival of the Incas; the archeological evidence suggests that the Paleo-Indians' first dispersal into the Americas occurred near the end of the last glacial period, around 16,500–13,000 years ago. The first Indians who reached Ecuador may have journeyed by land from North and Central America or by boat down the Pacific Ocean coastline. Much migrations to Ecuador may have come via the Amazon tributaries, others descended from northern South America, others ascended from the southern part of South America through the Andes.
They developed different languages while emerging as unique ethnic groups. Though their languages were unrelated, these groups developed similar groups of cultures, each based in different environments; the people of the coast developed a fishing and gathering culture. Over time these groups began to interact and intermingle with each other so that groups of families in one area became one community or tribe, with a similar language and culture. Many civilizations arose in Ecuador, such as the Valdivia Culture and Machalilla Culture on the coast, the Quitus, the Cañari; each civilization developed its own distinctive architecture and religious interests. In the highland Andes mountains, where life was more sedentary, groups of tribes cooperated and formed villages. Through wars and marriage alliances of their leaders, a group of nations formed confederations. One region consolidated under a confederation called the Shyris, which exercised organized trading and bartering between the different regions.
Its political and military power came under the rule of the Duchicela blood-line. When the Incas arrived, they found that these confederations were so developed that it took the Incas two generations of rulers—Topa Inca Yupanqui and Huayna Capac—to absorb them into the Inca Empire; the native confederations that gave them the most problems were deported to distant areas of Peru and north Argentina. A number of loyal Inca subjects from Peru and Bolivia were brought to Ecuador to prevent rebellion. Thus, the region of highland Ecuador became part of the Inca Empire in 1463 sharing the same language. In contrast, when the Incas made incursions into coastal Ecuador and the eastern Amazon jungles of Ecuador, they found both the environment and indigenous people more hostile. Moreover, when the Incas tried to subdue them, these indigenous people withdrew to the interior and resorted to guerrilla tactics; as a result, Inca expansion into the Amazon Basin and the Pacific coast of Ecuador was hampered.
The indigenous people of the Amazon jungle and coastal Ecuador remained autonomous until the Spanish soldiers and missionaries arrived in force. The Amazonian people and the Cayapas of Coastal Ecuador were the only groups to resist Inca and Spanish domination, maintaining their language and culture well into the 21st century. Before the arrival of the Spaniards, the Inca Empire was involved in a civil war; the untimely death of both the heir Ninan Cuchi and the Emperor Huayna Capac, from a European disease that spread into Ecuador, created a power vacuum between two factions. The northern faction headed by Atahualpa claims that Huayna Capac gave a verbal decree before his death about how the empire should be divided, he gave the territories pertaining to present-day Ecuador and northern Peru to his favorite son Atahualpa, to rule from Quito. He willed that his heart be buried in Quito, his favorite city, the rest of his body be buried with his ancestors in Cuzco. Huáscar did not recognize his fa
Proteins are essential nutrients for the human body. They are one of the building blocks of body tissue and can serve as a fuel source; as a fuel, proteins provide as much energy density as carbohydrates: 4 kcal per gram. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition. Proteins are polymer chains made of amino acids linked together by peptide bonds. During human digestion, proteins are broken down in the stomach to smaller polypeptide chains via hydrochloric acid and protease actions; this is crucial for the absorption of the essential amino acids that cannot be biosynthesized by the body. There are nine essential amino acids which humans must obtain from their diet in order to prevent protein-energy malnutrition and resulting death, they are phenylalanine, threonine, methionine, isoleucine and histidine. There has been debate as to whether there are 9 essential amino acids; the consensus seems to lean towards 9. There are five amino acids.
These five are alanine, aspartic acid, glutamic acid and serine. There are six conditionally essential amino acids whose synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress; these six are arginine, glycine, glutamine and tyrosine. Dietary sources of protein include both animals and plants: meats, dairy products and eggs, as well as grains and nuts. Vegans can get enough essential amino acids by eating plant proteins. Protein is a nutrient needed by the human body for maintenance. Aside from water, proteins are the most abundant kind of molecules in the body. Protein can be found in all cells of the body and is the major structural component of all cells in the body muscle; this includes body organs and skin. Proteins are used in membranes, such as glycoproteins; when broken down into amino acids, they are used as precursors to nucleic acid, co-enzymes, immune response, cellular repair, other molecules essential for life.
Additionally, protein is needed to form blood cells. Protein can be found in a wide range of food; the best combination of protein sources depends on the region of the world, cost, amino acid types and nutrition balance, as well as acquired tastes. Some foods are high in certain amino acids, but their digestibility and the anti-nutritional factors present in these foods make them of limited value in human nutrition. Therefore, one must consider digestibility and secondary nutrition profile such as calories, cholesterol and essential mineral density of the protein source. On a worldwide basis, plant protein foods contribute over 60 percent of the per capita supply of protein, on average. In North America, animal-derived foods contribute about 70 percent of protein sources. Meat, products from milk, eggs and fish are sources of complete protein. Whole grains and cereals are another source of proteins. However, these tend to be limiting in the amino acid lysine or threonine, which are available in other vegetarian sources and meats.
Examples of food staples and cereal sources of protein, each with a concentration greater than 7.0%, are buckwheat, rye, maize, wheat, sorghum and quinoa. Vegetarian sources of proteins include legumes, nuts and fruits. Legumes, some of which are called pulses in certain parts of the world, have higher concentrations of amino acids and are more complete sources of protein than whole grains and cereals. Examples of vegetarian foods with protein concentrations greater than 7 percent include soybeans, kidney beans, white beans, mung beans, cowpeas, lima beans, pigeon peas, wing beans, Brazil nuts, pecans, cotton seeds, pumpkin seeds, hemp seeds, sesame seeds, sunflower seeds. Food staples that are poor sources of protein include roots and tubers such as yams and sweet potato. Plantains, another major staple, are a poor source of essential amino acids. Fruits, while rich in other essential nutrients, are another poor source of amino acids; the protein content in roots and fruits is between 0 and 2 percent.
Food staples with low protein content must be complemented with foods with complete, quality protein content for a healthy life in children for proper development. A good source of protein is a combination of various foods, because different foods are rich in different amino acids. A good source of dietary protein meets two requirements: The requirement for the nutritionally indispensable amino acids under all conditions and for conditionally indispensable amino acids under specific physiological and pathological conditions The requirement for nonspecific nitrogen for the synthesis of the nutritionally dispensable amino acids and other physiologically important nitrogen-containing compounds such as nucleic acids and porphyrins. Healthy people eating a balanced diet need protein supplements; the table below presents the most important food groups as protein sources, from a worldwide perspective. It lists their respective performance as source of the limiting amino acids, in milligrams of limiting amino acid per gram of total protein in the food source.
The table reiterates the need for a balanced mix of
Citric acid is a weak organic acid that has the chemical formula C6H8O7. It occurs in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than a million tons of citric acid are manufactured every year, it is used as an acidifier, as a flavoring and chelating agent. A citrate is a derivative of citric acid. An example of the former, a salt is trisodium citrate; when part of a salt, the formula of the citrate ion is written as C6H5O3−7 or C3H5O3−3. Citric acid exists in greater than trace amounts in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have high concentrations of the acid; the concentrations of citric acid in citrus fruits range from 0.005 mol/L for oranges and grapefruits to 0.30 mol/L in lemons and limes. Within species, these values vary depending on the cultivar and the circumstances in which the fruit was grown. Industrial-scale citric acid production first began in 1890 based on the Italian citrus fruit industry, where the juice was treated with hydrated lime to precipitate calcium citrate, isolated and converted back to the acid using diluted sulfuric acid.
In 1893, C. Wehmer discovered. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian citrus exports. In 1917, American food chemist James Currie discovered certain strains of the mold Aspergillus niger could be efficient citric acid producers, the pharmaceutical company Pfizer began industrial-level production using this technique two years followed by Citrique Belge in 1929. In this production technique, still the major industrial route to citric acid used today, cultures of A. niger are fed on a sucrose or glucose-containing medium to produce citric acid. The source of sugar is corn steep liquor, hydrolyzed corn starch or other inexpensive sugary solutions. After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with calcium hydroxide to yield calcium citrate salt, from which citric acid is regenerated by treatment with sulfuric acid, as in the direct extraction from citrus fruit juice.
In 1977, a patent was granted to Lever Brothers for the chemical synthesis of citric acid starting either from aconitic or isocitrate/alloisocitrate calcium salts under high pressure conditions. This produced citric acid in near quantitative conversion under what appeared to be a reverse non-enzymatic Krebs cycle reaction. In 2007, worldwide annual production stood at 1,600,000 tons. More than 50% of this volume was produced in China. More than 50% was used as an acidity regulator in beverages, some 20% in other food applications, 20% for detergent applications and 10% for related applications other than food, such as cosmetics, pharmaceutics and in the chemical industry. Citric acid was first isolated in 1784 by the chemist Carl Wilhelm Scheele, who crystallized it from lemon juice, it can exist either as a monohydrate. The anhydrous form crystallizes from hot water, while the monohydrate forms when citric acid is crystallized from cold water; the monohydrate can be converted to the anhydrous form at about 78 °C.
Citric acid dissolves in absolute ethanol at 15 °C. It decomposes with loss of carbon dioxide above about 175 °C. Citric acid is considered to be a tribasic acid, with pKa values, extrapolated to zero ionic strength, of 5.21, 4.28 and 2.92 at 25 °C. The pKa of the hydroxyl group has been found, by means of 13C NMR spectroscopy, to be 14.4. The speciation diagram shows that solutions of citric acid are buffer solutions between about pH 2 and pH 8. In biological systems around pH 7, the two species present are the citrate ion and mono-hydrogen citrate ion; the SSC 20X hybridization buffer is an example in common use. Tables compiled for biochemical studies are available. On the other hand, the pH of a 1 mM solution of citric acid will be about 3.2. The pH of fruit juices from citrus fruits like oranges and lemons depends on the citric acid concentration, being lower for higher acid concentration and conversely. Acid salts of citric acid can be prepared by careful adjustment of the pH before crystallizing the compound.
See, for example, sodium citrate. The citrate ion forms complexes with metallic cations; the stability constants for the formation of these complexes are quite large because of the chelate effect. It forms complexes with alkali metal cations. However, when a chelate complex is formed using all three carboxylate groups, the chelate rings have 7 and 8 members, which are less stable thermodynamically than smaller chelate rings. In consequence, the hydroxyl group can be deprotonated, forming part of a more stable 5-membered ring, as in ammonium ferric citrate, 5Fe2·2H2O. Citric acid can be esterified at one or more of the carboxylic acid functional groups on the molecule, to form any of a variety of mono-, di-, tri-, mixed esters. Citrate is an intermediate in the TCA cycle, a central metabolic pathway for animals and bacteria. Citrate synthase catalyzes the condensation of oxaloacetate with acetyl CoA to form citrate. Citrate acts as the substrate for aconitase and is converted into aconitic acid.
The cycle ends with regeneration of oxaloacetate. This series
Peru the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, in the west by the Pacific Ocean. Peru is a megadiverse country with habitats ranging from the arid plains of the Pacific coastal region in the west to the peaks of the Andes mountains vertically extending from the north to the southeast of the country to the tropical Amazon Basin rainforest in the east with the Amazon river. Peruvian territory was home to several ancient cultures. Ranging from the Norte Chico civilization in the 32nd century BC, the oldest civilization in the Americas and one of the five cradles of civilization, to the Inca Empire, the largest state in pre-Columbian America, the territory now including Peru has one of the longest histories of civilization of any country, tracing its heritage back to the 4th millennia BCE; the Spanish Empire conquered the region in the 16th century and established a viceroyalty that encompassed most of its South American colonies, with its capital in Lima.
Peru formally proclaimed independence in 1821, following the military campaigns of José de San Martín and Simón Bolívar, the decisive battle of Ayacucho, Peru secured independence in 1824. In the ensuing years, the country enjoyed relative economic and political stability, which ended shortly before the War of the Pacific with Chile. Throughout the 20th century, Peru endured armed territorial disputes, social unrest, internal conflicts, as well as periods of stability and economic upswing. Alberto Fujimori was elected to the presidency in 1990. Fujimori left the presidency in 2000 and was charged with human rights violations and imprisoned until his pardon by President Pedro Pablo Kuczynski in 2017. After the president's regime, Fujimori's followers, called Fujimoristas, have caused political turmoil for any opposing faction in power causing Pedro Pablo Kuczynski to resign in March 2018; the sovereign state of Peru is a representative democratic republic divided into 25 regions. It is classified as an emerging market with a high level of human development and an upper middle income level with a poverty rate around 19 percent.
It is one of the region's most prosperous economies with an average growth rate of 5.9% and it has one of the world's fastest industrial growth rates at an average of 9.6%. Its main economic activities include mining, manufacturing and fishing; the country forms part of The Pacific Pumas, a political and economic grouping of countries along Latin America's Pacific coast that share common trends of positive growth, stable macroeconomic foundations, improved governance and an openness to global integration. Peru ranks high in social freedom. Peru has a population of 32 million, which includes Amerindians, Europeans and Asians; the main spoken language is Spanish, although a significant number of Peruvians speak Quechua or other native languages. This mixture of cultural traditions has resulted in a wide diversity of expressions in fields such as art, cuisine and music; the name of the country may be derived from Birú, the name of a local ruler who lived near the Bay of San Miguel, Panama City, in the early 16th century.
When his possessions were visited by Spanish explorers in 1522, they were the southernmost part of the New World yet known to Europeans. Thus, when Francisco Pizarro explored the regions farther south, they came to be designated Birú or Perú. An alternative history is provided by the contemporary writer Inca Garcilaso de la Vega, son of an Inca princess and a conquistador, he said the name Birú was that of a common Indian happened upon by the crew of a ship on an exploratory mission for governor Pedro Arias de Ávila, went on to relate more instances of misunderstandings due to the lack of a common language. The Spanish Crown gave the name legal status with the 1529 Capitulación de Toledo, which designated the newly encountered Inca Empire as the province of Peru. Under Spanish rule, the country adopted the denomination Viceroyalty of Peru, which became Republic of Peru after independence; the earliest evidences of human presence in Peruvian territory have been dated to 9,000 BC. Andean societies were based on agriculture, terracing.
Organization relied on reciprocity and redistribution because these societies had no notion of market or money. The oldest known complex society in Peru, the Norte Chico civilization, flourished along the coast of the Pacific Ocean between 3,000 and 1,800 BC; these early developments were followed by archaeological cultures that developed around the coastal and Andean regions throughout Peru. The Cupisnique culture which flourished from around 1000 to 200 BC along what is now Peru's Pacific Coast was an example of early pre-Incan culture; the Chavín culture that developed from 1500 to 300 BC was more of a religious than a political phenomenon, with their religious centre in Chavín de Huantar. After the decline of the Chavin culture around the beginning of the 1st century AD, a series of localized and specialized cultures rose and fell
The Andes or Andean Mountains are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. This range is about 7,000 km long, about 200 to 700 km wide, of an average height of about 4,000 m; the Andes extend from north to south through seven South American countries: Venezuela, Ecuador, Bolivia and Argentina. Along their length, the Andes are split into several ranges, separated by intermediate depressions; the Andes are the location of several high plateaus – some of which host major cities such as Quito, Bogotá, Medellín, Sucre, Mérida and La Paz. The Altiplano plateau is the world's second-highest after the Tibetan plateau; these ranges are in turn grouped into three major divisions based on climate: the Tropical Andes, the Dry Andes, the Wet Andes. The Andes Mountains are the world's highest mountain range outside Asia; the highest mountain outside Asia, Argentina's Mount Aconcagua, rises to an elevation of about 6,961 m above sea level.
The peak of Chimborazo in the Ecuadorian Andes is farther from the Earth's center than any other location on the Earth's surface, due to the equatorial bulge resulting from the Earth's rotation. The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to 6,893 m; the Andes are part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica. The etymology of the word Andes has been debated; the majority consensus is that it derives from the Quechua word anti, which means "east" as in Antisuyu, one of the four regions of the Inca Empire. The Andes can be divided into three sections: The Southern Andes in Chile. In the northern part of the Andes, the isolated Sierra Nevada de Santa Marta range is considered to be part of the Andes; the term cordillera comes from the Spanish word "cordel", meaning "rope".
The Andes range is about 200 km wide throughout its length, except in the Bolivian flexure where it is about 640 kilometres wide. The Leeward Antilles islands Aruba and Curaçao, which lie in the Caribbean Sea off the coast of Venezuela, were thought to represent the submerged peaks of the extreme northern edge of the Andes range, but ongoing geological studies indicate that such a simplification does not do justice to the complex tectonic boundary between the South American and Caribbean plates; the Andes are a Mesozoic–Tertiary orogenic belt of mountains along the Pacific Ring of Fire, a zone of volcanic activity that encompasses the Pacific rim of the Americas as well as the Asia-Pacific region. The Andes are the result of tectonic plate processes, caused by the subduction of oceanic crust beneath the South American Plate, it is the result of a convergent plate boundary between the Nazca Plate and the South American Plate The main cause of the rise of the Andes is the compression of the western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate.
To the east, the Andes range is bounded by several sedimentary basins, such as Orinoco, Amazon Basin, Madre de Dios and Gran Chaco, that separate the Andes from the ancient cratons in eastern South America. In the south, the Andes share a long boundary with the former Patagonia Terrane. To the west, the Andes end at the Pacific Ocean, although the Peru-Chile trench can be considered their ultimate western limit. From a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and a less rugged topography; the Andes Mountains contain large quantities of iron ore located in many mountains within the range. The Andean orogen has a series of oroclines; the Bolivian Orocline is a seaward concave bending in the coast of South America and the Andes Mountains at about 18° S. At this point, the orientation of the Andes turns from Northwest in Peru to South in Chile and Argentina; the Andean segment north and south of the orocline have been rotated 15° to 20° counter clockwise and clockwise respectively.
The Bolivian Orocline area overlaps with the area of maximum width of the Altiplano Plateau and according to Isacks the orocline is related to crustal shortening. The specific point at 18° S where the coastline bends is known as the "Arica Elbow". Further south lies the Maipo Orocline or Maipo Transition Zone located between 30° S and 38°S with a break in trend at 33° S. Near the southern tip of the Andes lies the Patagonian orocline; the western rim of the South American Plate has been the place of several pre-Andean orogenies since at least the late Proterozoic and early Paleozoic, when several terranes and microcontinents collided and amalgamated with the ancient cratons of eastern South America, by the South American part of Gondwana. The formation of the modern Andes began with the events of the Triassic when Pangaea began the break up that resulted in developing several rifts; the development continued through the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting and folding of sedimentary and metamorphic rocks of the ancient cratons to the east.
The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress and erosion. Tectonic forces above the subduction zone al
In botany, a staminode is an rudimentary, sterile or abortive stamen, which means that it does not produce pollen. Staminodes are inconspicuous and stamen-like occurring at the inner whorl of the flower, but are sometimes long enough to protrude from the corolla. Sometimes, the staminodes are modified to produce nectar, as in the Witch Hazel. Staminodes can be a critical characteristic for differentiating between species, for instance in the orchid genus Paphiopedilum, among the penstemons. In the case of Cannas, the petals are inconsequential and the staminodes are refined into eye-catching petal-like replacements. A spectacular example of staminode is given by Couroupita guianensis, a tropical tree growing in South America known as cannonball tree