Pollination
Pollination is the transfer of pollen from a male part of a plant to a female part of a plant enabling fertilisation and the production of seeds, most by an animal or by wind. Pollinating agents are animals such as insects and bats. Pollination occurs within a species; when pollination occurs between species it can produce hybrid offspring in nature and in plant breeding work. In angiosperms, after the pollen grain has landed on the stigma, it develops a pollen tube which grows down the style until it reaches an ovary. Sperm cells from the pollen grain move along the pollen tube, enter an ovum cell through the micropyle and fertilise it, resulting in the production of a seed. A successful angiosperm pollen grain containing the male gametes is transported to the stigma, where it germinates and its pollen tube grows down the style to the ovary, its two gametes travel down the tube to where the gametophyte containing the female gametes are held within the carpel. One nucleus fuses with the polar bodies to produce the endosperm tissues, the other with the ovule to produce the embryo Hence the term: "double fertilization".
In gymnosperms, the ovule is not contained in a carpel, but exposed on the surface of a dedicated support organ, such as the scale of a cone, so that the penetration of carpel tissue is unnecessary. Details of the process vary according to the division of gymnosperms in question. Two main modes of fertilization are found in gymnosperms. Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, whereas conifers and gnetophytes have sperm that are unable to swim but are conveyed to the egg along a pollen tube; the study of pollination brings together many disciplines, such as botany, horticulture and ecology. The pollination process as an interaction between flower and pollen vector was first addressed in the 18th century by Christian Konrad Sprengel, it is important in horticulture and agriculture, because fruiting is dependent on fertilization: the result of pollination. The study of pollination by insects is known as anthecology. Pollen germination has three stages; the pollen grain is dehydrated so that its mass is reduced enabling it to be more transported from flower to flower.
Germination only takes place after rehydration, ensuring that premature germination does not take place in the anther. Hydration allows the plasma membrane of the pollen grain to reform into its normal bilayer organization providing an effective osmotic membrane. Activation involves the development of actin filaments throughout the cytoplasm of the cell, which become concentrated at the point from which the pollen tube will emerge. Hydration and activation continue. In conifers, the reproductive structures are borne on cones; the cones are either pollen cones or ovulate cones, but some species are monoecious and others dioecious. A pollen cone contains hundreds of microsporangia carried on reproductive structures called sporophylls. Spore mother cells in the microsporangia divide by meiosis to form haploid microspores that develop further by two mitotic divisions into immature male gametophytes; the four resulting cells consist of a large tube cell that forms the pollen tube, a generative cell that will produce two sperm by mitosis, two prothallial cells that degenerate.
These cells comprise a reduced microgametophyte, contained within the resistant wall of the pollen grain. The pollen grains are dispersed by the wind to the female, ovulate cone, made up of many overlapping scales, each protecting two ovules, each of which consists of a megasporangium wrapped in two layers of tissue, the integument and the cupule, that were derived from modified branches of ancestral gymnosperms; when a pollen grain lands close enough to the tip of an ovule, it is drawn in through the micropyle by means of a drop of liquid known as a pollination drop. The pollen enters a pollen chamber close to the nucellus, there it may wait for a year before it germinates and forms a pollen tube that grows through the wall of the megasporangium where fertilisation takes place. During this time, the megaspore mother cell divides by meiosis to form four haploid cells, three of which degenerate; the surviving one develops as a megaspore and divides to form an immature female gametophyte. Two or three archegonia containing an egg develop inside the gametophyte.
Meanwhile, in the spring of the second year two sperm cells are produced by mitosis of the body cell of the male gametophyte. The pollen tube elongates and pierces and grows through the megasporangium wall and delivers the sperm cells to the female gametophyte inside. Fertilisation takes place when the nucleus of one of the sperm cells enters the egg cell in the megagametophyte’s archegonium. In flowering plants, the anthers of the flower produce microspores by meiosis; these undergo mitosis to form male gametophytes. Meanwhile, the ovules produce megaspores by meiosis, further division of these form the female gametophytes, which are strongly reduced, each consisting only of a few cells, one of, the egg; when a pollen grain adheres to the stigma of a carpel it germinates, developing a pollen tube that grows through the tissues of the style, entering the ovule through the micropyle. When the tube reaches the egg sac, two sperm cells pass through it into the female gametophyte and fertil
Johann Heinrich Friedrich Link
Johann Heinrich Friedrich Link was a German naturalist and botanist. Link was born at Hildesheim as a son of the minister August Heinrich Link, who taught him love of nature through collection of'natural objects', he studied medicine and natural sciences at the Hannoverschen Landesuniversität of Göttingen, graduated as MD in 1789, promoting on his thesis "Flora der Felsgesteine rund um Göttingen". One of his teachers was the famous natural scientist Johann Friedrich Blumenbach, he became a private tutor in Göttingen. In 1792 he became the first professor of the new department of chemistry and botany at the University of Rostock. During his stay at Rostock, he became an early follower of the antiphlogistic theory of Lavoisier, teaching about the existence of oxygen instead of phlogiston, he was a proponent of the attempts of Richter to involve mathematics in chemistry, introducing stoichiometry in his chemistry lessons. In 1806 he set up the first chemical laboratory at Rostock in the "Seminargebäude".
He began to write an abundant number of articles and books on the most different subjects, such as physics and chemistry and mineralogy, botany and zoology, natural philosophy and ethics and early history. He was twice elected rector of the university. In 1793 he married Charlotte Juliane Josephi, sister of his colleague at the university Prof. Wilhelm Josephi. During 1797–1799 he visited Portugal with Count Johann Centurius Hoffmannsegg, a botanist and ornithologist from Dresden; this trip made him choose botany as his main scientific calling. In 1800 he was elected to the prestigious Leopoldina Academy, the oldest school for natural history in Europe. In 1808 he was awarded a prize at the Academy of Saint Petersburg for his monography Von der Natur und den Eigenschaften des Lichts, his scientific reputation grew and became known. In 1811 he was appointed professor of chemistry and botany at Breslau university, where he was elected twice rector of the university. After the death of Carl Ludwig Willdenow in 1815, he became professor of natural history, curator of the herbarium and director of the botanic garden in Berlin until he died.
This period became the most fruitful period of his academic life. He augmented the collection of the garden to many of them rare plants, he worked in close collaboration with conservator at the botanical garden. In 1827 he named with him the cacti genera Melocactus. Most of the fungi that he named, are still recognised under the original name, proving the high quality of his work, he was elected member of the Berlin Academy of Science and many other scientific societies, including the Royal Swedish Academy of Sciences, which elected him a foreign member in 1840. He trained a whole new generation such as Christian Gottfried Ehrenberg. Throughout his life, he travelled extensively throughout Europe, he benefited including Arabic and ancient Sanskrit. He died in Berlin on 1 January 1851 84 years old, he was succeeded by Alexander Heinrich Braun, He is recognised as one of the last scientists of the 19th century with a universal knowledge. Link was one of the few German botanists of his time, who aimed at a complete understanding of plants, through a systematic anatomical and physiological research.
His most important work is the Handbuch zur Erkennung der nutzbarsten und am häufigsten vorkommenden Gewächse. Grundlehren der Anatomie und Physiologie der Pflanzen. Nachträge zu den Grundlehren etc. Die Urwelt und das Altertum, erläutert durch die Naturkunde. Handbuch zur Erkennung der nutzbarsten und am häufigsten vorkommenden Gewächse. Berlin: Haude und Spener. Retrieved 5 February 2015. Digital edition by State Library Düsseldorf Erster Theil. Zweiter Theil. Dritter Theil. Das Altertum und der Übergang zur neuern Zeit, he published together with Friedrich Otto: Icones plantarum selectarum horti regii botanici Berolinensis He published with Christoph Friedrich Otto Icones plantarum rariorum horti regii botanici Berolinensis He published together with count von Hoffmansegg Flore
Starch
Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as energy storage, it is the most common carbohydrate in human diets and is contained in large amounts in staple foods like potatoes, maize and cassava. Pure starch is a white and odorless powder, insoluble in cold water or alcohol, it consists of two types of molecules: the branched amylopectin. Depending on the plant, starch contains 20 to 25% amylose and 75 to 80% amylopectin by weight. Glycogen, the glucose store of animals, is a more branched version of amylopectin. In industry, starch is converted into sugars, for example by malting, fermented to produce ethanol in the manufacture of beer and biofuel, it is processed to produce many of the sugars used in processed foods. Mixing most starches in warm water produces a paste, such as wheatpaste, which can be used as a thickening, stiffening or gluing agent; the biggest industrial non-food use of starch is as an adhesive in the papermaking process.
Starch can be applied to parts of some garments before ironing. The word "starch" is from a Germanic root with the meanings "strong, strengthen, stiffen". Modern German Stärke is related; the Greek term for starch, "amylon", is related. It provides the root amyl, used as a prefix for several 5-carbon compounds related to or derived from starch. Starch grains from the rhizomes of Typha as flour have been identified from grinding stones in Europe dating back to 30,000 years ago. Starch grains from sorghum were found on grind stones in caves in Ngalue, Mozambique dating up to 100,000 years ago. Pure extracted wheat starch paste was used in Ancient Egypt to glue papyrus; the extraction of starch is first described in the Natural History of Pliny the Elder around AD 77–79. Romans used it in cosmetic creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat halva. Rice starch as surface treatment of paper has been used in paper production in China since 700 CE.
In addition to starchy plants consumed directly, by 2008 66 million tonnes of starch were being produced per year worldwide. In 2011 production was increased to 73 million ton. In the EU the starch industry produced about 8.5 million tonnes in 2008, with around 40% being used for industrial applications and 60% for food uses, most of the latter as glucose syrups. In 2017 EU production was 11 million ton of which 9,4 million ton was consumed in the EU and of which 54% were starch sweeteners. US produced about 27,5 million ton starch in 2017 of which about 8,2 million ton high fructose syrup and 6,2 million ton glucose syrups and 2,5 million ton starch products, the rest of the starch was used for producing ethanol. Most green plants use starch as their energy store; the extra glucose is changed into starch, more complex than glucose. An exception is the family Asteraceae. Inulin-like fructans are present in grasses such as wheat, in onions and garlic and asparagus. In photosynthesis, plants use light energy to produce glucose from carbon dioxide.
The glucose is used to generate the chemical energy required for general metabolism, to make organic compounds such as nucleic acids, lipids and structural polysaccharides such as cellulose, or is stored in the form of starch granules, in amyloplasts. Toward the end of the growing season, starch accumulates in twigs of trees near the buds. Fruit, seeds and tubers store starch to prepare for the next growing season. Glucose is soluble in water, binds with water and takes up much space and is osmotically active. Glucose molecules are bound in starch by the hydrolyzed alpha bonds; the same type of bond is found in the animal reserve polysaccharide glycogen. This is in contrast to many structural polysaccharides such as chitin and peptidoglycan, which are bound by beta bonds and are much more resistant to hydrolysis. Plants produce starch by first converting glucose 1-phosphate to ADP-glucose using the enzyme glucose-1-phosphate adenylyltransferase; this step requires energy in the form of ATP. The enzyme starch synthase adds the ADP-glucose via a 1,4-alpha glycosidic bond to a growing chain of glucose residues, liberating ADP and creating amylose.
The ADP-glucose is certainly added to the non-reducing end of the amylose polymer, as the UDP-glucose is added to the non-reducing end of glycogen during glycogen synthesis. Starch branching enzyme introduces 1,6-alpha glycosidic bonds between the amylose chains, creating the branched amylopectin; the starch debranching enzyme isoamylase removes some of these branches. Several isoforms of these enzymes exist, leading to a complex synthesis process. Glycogen and amylopectin have similar structure, but the former has about one branch point per ten 1,4-alpha bonds, compared to about one branch point per thirty 1,4-alpha bonds in amylopectin. Amylopectin is synthesized from ADP-glucose while mammals and fungi synthesize glycogen from UDP-glucose. In addition to starch synthesis in plants, starch can be synthesized from non-food starch mediated by an enzyme cocktail. In this cell-free biosystem, beta-1,4-glycosidic bond-linked cellulose is hydrolyzed to cello
Lobelia deckenii
Lobelia deckenii is a species of giant lobelia of the mountains of East Africa. It grows in moist areas, such as valley bottoms and moorland, in contrast to Lobelia telekii which grows in a similar but drier habitat; these two species produce occasional hybrids. Lobelia deckenii plants produce multiple rosettes; each rosette grows for several decades, produces a single large inflorescence and hundreds of thousands of seeds dies. Because individual plants have multiple rosettes, they survive to reproduce and plants with more rosettes flower more frequently, it is iteroparous. Lobelia deckenii plants form between one and eighteen rosettes which are connected underground; the individual rosettes grow in the alpine environment, may take decades to reach reproductive size. The rosette that produces an inflorescence dies after flowering, but the remaining connected rosettes live on. Lobelia deckenii is the only alpine species of lobelia, native to Kilimanjaro, occurring between 3,800 and 4,300 m. Lobelia deckenii ssp. keniensis is the variety of Lobelia deckenii that occurs on Mount Kenya, between 3,300 and 4,600 m.
It is eaten less by rock hyrax than Lobelia telekii, which occurs more in hyrax habitat. The lobelia species on Mount Kenya are both pollinated by birds the scarlet-tufted sunbird and the alpine chat; this species of giant lobelia is known for the reservoirs of water held in its rosettes, which freeze at night and protect the apical meristem, contained in a dense central leaf bud. When this reservoir is drained, the temperature of the inner meristem drops below freezing, which does not occur when the fluid is left intact; the crescent-shaped ice cubes formed in these rosettes gave rise to the nickname, "gin and tonic lobelia". Dressler, S.. "Lobelia deckenii". African plants – a Photo Guide. Frankfurt/Main: Forschungsinstitut Senckenberg
Dicotyledon
The dicotyledons known as dicots, are one of the two groups into which all the flowering plants or angiosperms were divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons. There are around 200,000 species within this group; the other group of flowering plants were called monocotyledons or monocots having one cotyledon. These two groups formed the two divisions of the flowering plants. From the 1990s onwards, molecular phylogenetic research confirmed what had been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor. Rather, a number of lineages, such as the magnoliids and groups now collectively known as the basal angiosperms, diverged earlier than the monocots did; the traditional dicots are thus a paraphyletic group. The largest clade of the dicotyledons are known as the eudicots, they are distinguished from all other flowering plants by the structure of their pollen.
Other dicotyledons and monocotyledons have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi. Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences between monocots and eudicots. Many early-diverging dicot groups have "monocot" characteristics such as scattered vascular bundles, trimerous flowers, non-tricolpate pollen. In addition, some monocots have dicot characteristics such as reticulated leaf veins. Traditionally the dicots have been called the Dicotyledones, at any rank. If treated as a class, as in the Cronquist system, they could be called the Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots were treated as a separate class, the Rosopsida, or as several separate classes; the remaining dicots may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense. The following lists show the orders in the Angiosperm Phylogeny Group APG IV system traditionally called dicots, together with the older Cronquist system. In the Dahlgren and the Thorne systems, the subclass name Magnoliidae was used for the dicotyledons; this is the case in some of the systems derived from the Cronquist system. For each system, only the superorders are listed; the sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system as depicted by Reveal is: Calyciflorae World list of dicot species via the Catalogue of Life Tree browser for dicot orders and genera with species counts and estimates via the Catalogue of Life
Synapomorphy and apomorphy
In phylogenetics and synapomorphy refer to derived characters of a clade: characters or traits that are derived from ancestral characters over evolutionary history. An apomorphy is a character, different from the form found in an ancestor, i.e. an innovation, that sets the clade apart from other clades. A synapomorphy is a shared apomorphy. In other words, it is an apomorphy shared by members of a monophyletic group, thus assumed to be present in their most recent common ancestor. An apomorphy is a character, different from the form found in an ancestor, i.e. an innovation, that sets the clade apart from other clades. A synapomorphy is a shared apomorphy. In other words, it is an apomorphy shared by members of a monophyletic group, thus assumed to be present in their most recent common ancestor. In most groups of mammals, the vertebral column is conserved, with the same number of vertebrae found in the neck of a giraffe, for example, as in mammals with shorter necks. However, in the Afrotheria clade, which includes elephant shrews, golden moles and elephants, there is an increase in the number of thoracolumbar vertebrae.
This is a synapomorphy of the clade: a shared feature considered to be derived from a common ancestor. The word synapomorphy—coined by German entomologist Willi Hennig—is derived from the Greek words σύν, syn = shared; these phylogenetic terms are used to describe different patterns of ancestral and derived character or trait states as stated in the above diagram in association with synapomorphies. Symplesiomorphy – an ancestral trait shared by two or more taxa. Plesiomorphy – a symplesiomorphy discussed in reference to a more derived state. Pseudoplesiomorphy – is a trait that cannot be identified as neither a plesiomorphy nor an apomorphy, a reversal. Reversal – is a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait. Convergence – independent evolution of a similar trait in two or more taxa. Apomorphy – a derived trait. Apomorphy shared by two or more taxa and inherited from a common ancestor is synapomorphy. Apomorphy unique to a given taxon is autapomorphy.
Synapomorphy/Homology – a derived trait, found in some or all terminal groups of a clade, inherited from a common ancestor, for which it was an autapomorphy. Underlying synapomorphy – a synapomorphy, lost again in many members of the clade. If lost in all but one, it can be hard to distinguish from an autapomorphy. Autapomorphy – a distinctive derived trait, unique to a given taxon or group. Homoplasy in biological systematics is when a trait has been gained or lost independently in separate lineages during evolution; this convergent evolution leads to species independently sharing a trait, different from the trait inferred to have been present in their common ancestor. Parallel Homoplasy – derived trait present in two groups or species without a common ancestor due to convergent evolution. Reverse Homoplasy – trait present in an ancestor but not in direct descendants that reappears in descendants. Hemiplasy A new method of measuring phylogenetic characteristics is the use of Relative Apparent Synapomorphy Analysis.
The objective of analysis is to determine if a given characteristic is common between taxa as a result of either shared ancestors or the process of convergence. This method allows for several advantages such as computational efficiency and it administers an unbiased and reliable measure of phylogenetic signal; the concept of synapomorphy is relative to a given clade in the tree of life. What counts as a synapomorphy for one clade may well be a primitive character or plesiomorphy at a less inclusive or nested clade. For example, the presence of mammary glands is a synapomorphy for mammals in relation to tetrapods but is a symplesiomorphy for mammals in relation to one another—rodents and primates, for example. So the concept can be understood as well in terms of "a character newer than" and "a character older than" the apomorphy: mammary glands are evolutionarily newer than vertebral column, so mammary glands are an autapomorphy if vertebral column is an apomorphy, but if mammary glands are the apomorphy being considered vertebral column is a plesiomorphy.
Cladograms are diagrams. These illustrations are accurate predictive device in modern genetics, they are depicted in either tree or ladder form. Synapomorphies create evidence for historical relationships and their associated hierarchical structure. Evolutionarily, a synapomorphy is the marker for the most recent common ancestor of the monophyletic group consisting of a set of taxa in a cladogram. Cladistics, Berkeley
Pentaphragma
Pentaphragma is a genus of flowering plants. Pentaphragma is the sole genus in a family in the order Asterales; these species are fleshy herbs, with asymmetrical leaf blades. They are found in Southeast Asia. Pentaphragma is rayless, but develops rays in at least one of the species studied; this is interpreted as related to secondary woodiness or upright habit within a predominantly herbaceous phylad. The vessel elements of Pentaphragma have features universally interpreted as primitive in dicotyledons: scalariform perforation plates with numerous bars; the presence of occasional scalariform perforation plates aberrant, in secondary xylem of families of Asterales sensu lato - Campanulaceae, Pentaphragmataceae and Asteraceae - can be attributed to paedomorphosis, extending these plates into secondary xylem from primary xylem. Raylessness in Pentaphragma can be described in terms of secondary paedomorphosis; the fact that fiber-tracheids are shorter than vessel elements in Pentaphragma is believed related to raylessness because some fiber-tracheids are produced from'potential' ray areas.
Pentaphragma bicolorPentaphragma pendulaPentaphragma longisepalumPentaphragma lambirensePentaphragma prostratum www.mobot.org
