The rosids are members of a large clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms. The clade is divided into 16 to 20 orders, depending upon circumscription and classification; these orders, in turn, together comprise about 140 families. Fossil rosids are known from the Cretaceous period. Molecular clock estimates indicate that the rosids originated in the Aptian or Albian stages of the Cretaceous, between 125 and 99.6 million years ago. The name is based upon the name "Rosidae", understood to be a subclass. In 1967, Armen Takhtajan showed that the correct basis for the name "Rosidae" is a description of a group of plants published in 1830 by Friedrich Gottlieb Bartling; the clade was renamed "Rosidae" and has been variously delimited by different authors. The name "rosids" is informal and not assumed to have any particular taxonomic rank like the names authorized by the ICBN; the rosids are monophyletic based upon evidence found by molecular phylogenetic analysis.
Three different definitions of the rosids were used. Some authors included the orders Vitales in the rosids. Others excluded both of these orders; the circumscription used in this article is that of the APG IV classification, which includes Vitales, but excludes Saxifragales. The rosids and Saxifragales form the superrosids clade; this is one of three groups that compose the Pentapetalae, the others being Dilleniales and the superasterids. The rosids consist of two groups: the eurosids; the eurosids, in turn, are divided into two groups: malvids. The rosids consist of 17 orders. In addition to Vitales, there are 8 orders in malvids; some of the orders have only been recognized. These are Vitales, Crossosomatales and Huerteales; the phylogeny of Rosids shown below is adapted from the Angiosperm Phylogeny Group website. The nitrogen-fixing clade contains a high number of actinorhizal plants. Not all plants in this clade are actinorhizal, however. Media related to Rosids at Wikimedia Commons
Tyge W. Böcher
Tyge Wittrock Böcher was a Danish botanist, evolutionary biologist, plant ecologist and phytogeographer. He was born in Copenhagen to wife Cathinca née Andersen. Steen B. Böcher, professor of geography, was his brother. Tyge Böcher was professor of botany at the University of Copenhagen from 1954 to 1979, he was a prolific scientific writer, leaving some 250 scholarly articles. His scientific research covered as diverse phylogenetic lineages as vascular plants, bryophytes and algae and a broad set of disciplines from anatomy and evolution of plant species to the ecology of plant populations and plant communities, he was interested in chromosomal and ecological races of plant species. He did field work in Greenland, various European mountain regions and in Argentina, his investigation of the Greenland flora were ground-breaking. He was a co-founder of Flora Europaea and he authored the Flora of Greenland; the genus Boechera Á. Löve & D. Löve is named after him. Beiträge zur Zytologie der Gattung Anemone.
Botanisk Tidsskrift 42: 183-206. 1932. Keywords: Pulsatilla pratensis, Pulsatilla vernalis, Pulsatilla vulgaris, cytology Phytogeographical studies of the Greenland flora based upon investigations of the coast between Scoresby Sound and Angmagsalik. Meddelelser om Grønland 104, 3. 1933. Keywords: Greenland, plant geography Studies on the vegetation of the East coast of Greenland between Scoresby Sound and Angmagsalik. Meddelelser om Grønland 104, 4. 1933 Keywords: Greenland, arctic vegetation Botany. Appendix to Ejnar Mikkelsen: The Blosseville Coast of East Greenland. Geographical Journal 81: 400-402. 1933. Keywords: Greenland, arctic vegetation Om en måde til undersøgelse af konstans, skudtæthed og homogenitet. Botanisk Tidsskrift 43: 278-304. 1935. Keywords: methodology, vegetation cytological studies on Campanula rotundifolia. Hereditas 22: 269-277. 1936. Udbredelsen af Ericaceæ, Vacciniaceæ og Empetraceæ i Danmark. Summary: The distribution of the Ericaceæ, Vacciniaceæ and Empetraceæ in Denmark. Botanisk Tidsskrift 44: 5-40, 12 maps.
1937. Keywords: Calluna vulgaris, Empetrum nigrum, Erica tetralix, Vaccinium myrtillus, Vaccinium oxycoccos, Vaccinium uliginosum, Vaccinium vitis-idaea, plant geography Nogle studier over Færøernes alpine vegetation. Botanisk Tidsskrift 44: 154-201. 1937. Keywords: Faroe Islands, vegetation Biological distributional types in the flora of Greenland. A study on the flora and plant-geography of South Greenland and East Greenland between Cape Farewell and Scoresby Sound. Doctoral thesis, University of Copenhagen. Meddelelser om Grønland 106, 2: 1-136. 1938. Keywords: Greenland, plant geography cytological studies in the genus Ranunculus. Dansk Botanisk Arkiv 9, 4: 1-33. 1938. Zur Zytologie einiger arktischen und borealen Blütenpflanzen. Svensk Botanisk Tidskrift 32: 346-361. 1938. Studies on the plant-geography of the North-Atlantic heath-formation. I; the heaths of the Faeroes. Biologiske Meddelelser / Kongelige Danske Videnskabernes Selskab 15, 3: 1-64. 1940. Keywords: vegetation Introductory studies on variation and life-forms in Brunella vulgaris L. Dansk Botanisk Arkiv 10, 3: 1-15.
1940. Keywords: ecotype Vegetationen på Randbøl Hede. Med særlig hensyntagen til det fredede areal. Biologiske Skrifter / Kongelige Danske Videnskabernes Selskab 1, 3: 1-234. 1941. Keywords: Denmark, vegetation Beiträge zur Pflanzengeographie und Ökologie dänischer Vegetation. 1. Über die Flechtenheiden und Dünen der Insel Läsö. Biologiske Skrifter / Kongelige Danske Videnskabernes Selskab 2, 1: 1-38. 1941. Keywords: Denmark, Lichen, vegetation On the origin of Saxifraga nathorsti v. Hayek. Meddelelser om Grønland 131, 2: 1-14. 1941. Keywords: Greenland, speciation Vegetationsstudier på halvøen Ulvshale. Botanisk Tidsskrift 46: 1-42. 1942. Keywords: Denmark, vegetation Studies on variation and biology in Plantago lanceolata L. Dansk Botanisk Arkiv. 11,3: 1-18. 1943. Keywords: ecotype Studies on the plant geography of the North-Atlantic heath formation II. Danish dwarf shrub communities in relation to those of Northern Europe. Biologiske Skrifter / Kongelige Danske Videnskabernes Selskab 2, 7: 1-130. 1943. Keywords: Denmark, vegetation Nordische Verbreitungstypen.
Svensk Botanisk Tidskrift 37: 352-370. 1943. Keywords: Scandinavia, plant geography Polyploidy in the genus Koeleria. Hereditas 29: 499-500. 1943. Keywords: cytology, Koeleria glauca, Koeleria pyramidata The leaf size of Veronica officinalis in relation to genetic and environmental factors. Dansk Botanisk Arkiv 11, 7: 1-20. 1944. Keywords: cytology, ecotype Beiträge zur Pflanzengeographie und Ökologie Dänischer Vegetation. II. Über die Waldsaum- und Graskrautgesellschaften trockener und halbtrockener Böden der Insel Seeland mit besonderer Berücksichtigung der Strandabhänge und Strandebenen. Biologiske Skrifter / Kongelige Danske Videnskabernes Selskab 4, 1: 1-163. 1945. Keywords: Denmark, plant geography, vegetation Meiosis in Anemone apennina with special reference to chiasma localisation. Hereditas 31: 221-237. 1945. Keywords: cytology Ochromonas viridis sp.n. A green flagellate belonging to Chrysomonadinae. Videnskabelige meddelelser fra Dansk Naturhistorisk Forening 108: 233-238. 1945. Keywords: algae Græs-urte-vegetationen pa Høje Møn.
Botanisk Tidsskrift 48: 1-45. 1946. Keywords: Denmark, vegetation Dichothrix gelatinosa sp. n. Its structure and resting organs. Biologiske Skrifter / Kongelige Danske Videnskabernes Selskab 4, 4: 1-14. 1946. Keywords: algae Some experiments to elucidate t
Boechera pulchra is a perennial plant in the mustard family found in the Mojave Desert and other dry regions of southern and eastern California and Nevada, the Colorado Plateau and Canyonlands region of the southwestern United States below 8,000 feet elevation. A long-lived perennial, it is 300–750 mm tall from a woody base. Eight to twenty purple white, flowers are borne in a unbranched raceme. Petals are 9–16 mm long and 2–5 mm wide. Sepals are hairy. Media related to Boechera pulchra at Wikimedia Commons
Boechera sparsiflora is a species of rockcress known by the common names sicklepod rockcress and elegant rockcress. It is native to western North America from California to Utah to Yukon, where it can be found in a number of habitats; this is a coarsely hairy perennial herb growing one or more thick stems from a caudex. The stem may branch or not and it reaches up to 90 centimeters in maximum height; the leaves vary in shape from linear to arrowhead-like and may not have toothed edges. They are hairy and up to 8 or 10 centimeters long; the raceme inflorescence bears a number of flowers with spoon-shaped petals about a centimeter long in shades of purple or pink. The fruit is a large, curved silique 6 to 12 centimeters long Media related to Boechera sparsiflora at Wikimedia Commons Jepson Manual Treatment USDA Plants Profile "Boechera sparsiflora". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Photo gallery Boechera sparsiflora at The Plant List
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Trichomes, from the Greek τρίχωμα meaning "hair", are fine outgrowths or appendages on plants, algae and certain protists. They are of diverse function. Examples are hairs, glandular hairs and papillae. A covering of any kind of hair on a plant is an indumentum, the surface bearing them is said to be pubescent. Certain filamentous, algae have the terminal cell produced into an elongate hair-like structure called a trichome; the same term is applied to such structures in some cyanobacteria, such as Spirulina and Oscillatoria. The trichomes of cyanobacteria may be unsheathed, as in Oscillatoria, or sheathed, as in Calothrix; these structures play an important role in preventing soil erosion in cold desert climates. The filamentous sheaths form a persistent sticky network. Trichomes on plants are epidermal outgrowths of various kinds; the terms emergences or prickles refer to outgrowths. This distinction is not always applied. There are nontrichomatous epidermal cells that protrude from the surface. A common type of trichome is a hair.
Plant hairs may be multicellular, branched or unbranched. Multicellular hairs may have several layers of cells. Branched hairs can be tufted, or stellate, as in Arabidopsis thaliana. Another common type of trichome is the scale or peltate hair, that has a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind. Common examples are the leaf scales of bromeliads such as the pineapple and sea buckthorn. Any of the various types of hairs may be glandular, producing some kind of secretion, such as the essential oils produced by mints and many other members of the family Lamiaceae. In describing the surface appearance of plant organs, such as stems and leaves, many terms are used in reference to the presence and appearance of trichomes; the most basic terms used are glabrous—lacking hairs— and pubescent—having hairs. Details are provided by: glabrous, glabrate -- lacking trichomes. Several basic functions or advantages of having surface hairs can be listed.
It is that in many cases, hairs interfere with the feeding of at least some small herbivores and, depending upon stiffness and irritability to the palate, large herbivores as well. Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells. In windy locations, hairs break up the flow of air across the plant surface. Dense coatings of hairs reflect sunlight, protecting the more delicate tissues underneath in hot, open habitats. In addition, in locations where much of the available moisture comes from fog drip, hairs appear to enhance this process by increasing the surface area on which water droplets can accumulate. Both trichomes and root hairs, the rhizoids of many vascular plants, are lateral outgrowths of a single cell of the epidermal layer. Root hairs form from the hair-forming cells on the epidermis of a plant root. Root hairs vary between 5 and 17 micrometres in diameter, 80 to 1,500 micrometres in length. Root hairs can survive for two to three weeks and die off.
At the same time new root hairs are continually being formed at the top of the root. This way, the root hair coverage stays the same, it is therefore understandable that repotting must be done with care, because the root hairs are being pulled off for the most part. This is; the genetic control of patterning of trichomes and roots hairs shares similar control mechanisms. Both processes involve a core of related transcription factors that control the initiation and development of the epidermal outgrowth. Activation of genes that encode specific protein transcription factors are the major regulators of cell fate to produce trichomes or root hairs; when these genes are activated in a leaf epidermal cell, the formation of a trichrome is initiated within that cell. GL1, GL3. and TTG1 activate negative regulators, which serve to inhibit trichrome formation in neighboring cells. This system controls the spacing of trichomes on the leaf surface. Once trichome are developed they may branch. In contrast, root hairs only branch.
During the formation of trichomes and root hairs, many enzymes are regulated. For example, just prior to the root hair development, there is a point of elevated phosphorylase activity; the type and absence and location of trichomes are important diagnostic characters in plant identification and plant taxonomy. In forensic examination, plants such as Cannabis sativa can be identified by microscopic examination of the trichomes. Althoug
In botany, apomixis was defined by Hans Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. Its etymology is Greek for "away from" + "mixing"; this definition notably does not mention meiosis. Thus "normal asexual reproduction" of plants, such as propagation from cuttings or leaves, has never been considered to be apomixis, but replacement of the seed by a plantlet or replacement of the flower by bulbils were categorized as types of apomixis. Apomictically produced offspring are genetically identical to the parent plant; some authors included all forms of asexual reproduction within apomixis, but that generalization of the term has since died out. In flowering plants, the term "apomixis" is used in a restricted sense to mean agamospermy, i.e. clonal reproduction through seeds. Although agamospermy could theoretically occur in gymnosperms, it appears to be absent in that group. Apogamy is a related term. In plants with independent gametophytes, the term is still used interchangeably with "apomixis", both refer to the formation of sporophytes by parthenogenesis of gametophyte cells.
Male apomixis involves replacement of the genetic material of egg by the pollen that of egg Because apomictic plants are genetically identical from one generation to the next, each lineage has some of the characters of a true species, maintaining distinctions from other apomictic lineages within the same genus, while having much smaller differences than is normal between species of most genera. They are therefore called microspecies. In some genera, it is possible to identify and name hundreds or thousands of microspecies, which may be grouped together as species aggregates listed in floras with the convention "Genus species agg.". In some plant families, genera with apomixis are quite common, for example in Asteraceae and Rosaceae. Examples of apomixis can be found in the genera Crataegus, Sorbus, Poa, Nardus stricta and Taraxacum. Apomixis is reported to occur in about 10% of globally extant ferns. Among polystichoid ferns, apomixis evolved several times independently in three different clades.
Although the evolutionary advantages of sexual reproduction are lost, apomixis can pass along traits fortuitous for evolutionary fitness. As Jens Clausen put itThe apomicts have discovered the effectiveness of mass production long before Mr Henry Ford applied it to the production of the automobile.... Facultative apomixis... does not prevent variation. Facultative apomixis means that apomixis does not always occur, i.e. sexual reproduction can happen. It appears that all apomixis in plants is facultative; the gametophytes of bryophytes, less ferns and lycopods can develop a group of cells that grow to look like a sporophyte of the species but with the ploidy level of the gametophyte, a phenomenon known as apogamy. The sporophytes of plants of these groups may have the ability to form a plant that looks like a gametophyte but with the ploidy level of the sporophyte, a phenomenon known as apospory. See androgenesis and androclinesis described below, a type of male apomixis that occurs in a conifer, Cupressus dupreziana.
Agamospermy, asexual reproduction through seeds, occurs in flowering plants through many different mechanisms and a simple hierarchical classification of the different types is not possible. There are as many different usages of terminology for apomixis in angiosperms as there are authors on the subject. For English speakers, Maheshwari 1950 is influential. German speakers might prefer to consult Rutishauser 1967; some older text books on the basis of misinformation attempted to reform the terminology to match the term parthenogenesis as it is used in zoology, this continues to cause much confusion. Agamospermy occurs in two forms: In gametophytic apomixis, the embryo arises from an unfertilized egg cell in a gametophyte, produced from a cell that did not complete meiosis. In adventitious embryony, an embryo is formed directly from nucellus or integument tissue. Maheshwari used the following simple classification of types of apomixis in flowering plants: Nonrecurrent apomixis: In this type "the megaspore mother cell undergoes the usual meiotic divisions and a haploid embryo sac is formed.
The new embryo may arise either from the egg or from some other cell of the gametophyte." The haploid plants have half as many chromosomes as the mother plant, "the process is not repeated from one generation to another". See parthenogenesis and apogamy below. Recurrent apomixis, is now more called gametophytic apomixis: In this type, the megagametophyte has the same number of chromosomes as the mother plant because meiosis was not completed, it arises either from an archesporial cell or from some other part of the nucellus. Adventive embryony called sporophytic apomixis, sporophytic budding, or nucellar embryony: Here there may be a megagametophyte in the ovule, but the embryos do not arise from the cells of the gametophyte.