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Nostoc Commune
''Nostoc commune'' is a species of cyanobacterium in the family Nostocaceae. Common names include star jelly, witch's butter, mare's eggs. It is the type species of the genus ''Nostoc'' and is cosmopolitan in distribution. Description ''Nostoc commune'' is a colonial species of cyanobacterium. It initially forms a small, hollow gelatinous globule which grows and becomes leathery, flattened and convoluted, forming a gelatinous mass with other colonies growing nearby. Inside the thin sheath are numerous unbranched hair-like structures called trichomes formed of short cells in a string. The cells are bacteria and thus have no nucleus nor internal membrane system. To multiply, they form two new cells when they divide by binary fission. Along the trichomes, larger specialist nitrogen-fixing cells called heterocysts occur between the ordinary cells. When wet, ''Nostoc commune'' is bluish-green, olive green or brown but in dry conditions it becomes an inconspicuous, crisp brownish m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean Pierre Étienne Vaucher
Jean Pierre Étienne Vaucher (17 April 1763 – 5 or 6 January 1841) was a Swiss Protestant pastor and botanist who was a native of the Republic of Geneva. He studied theology at Geneva, and from 1795 to 1821 was a pastor at the Church of Saint-Gervais. From 1808 to 1840 he was a professor of church history at the University of Geneva, and for a number of years he also taught classes in botany. Among his better-known students were botanist Augustin Pyramus de Candolle (1778-1841), scientist Hans Conrad Escher von der Linth (1767-1823) and Charles Albert of Sardinia, Charles-Albert (1798-1849), the future King of Sardinia. Vaucher is remembered for his research involving the developmental history of algae. In his 1803 treatise ''Histoire des Conferves d'eau douce'', he described the process of Sexual conjugation, conjugation in certain algae as a distinct sexual process. The phenomena of conjugation is a means of fertilization that takes place in green algae such as ''Spirogyra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmopolitan Distribution
In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and environmental conditions, though this is not always so. Killer whales ( orcas) are among the most well-known cosmopolitan species on the planet, as they maintain several different resident and transient (migratory) populations in every major oceanic body on Earth, from the Arctic Circle to Antarctica and every coastal and open-water region in-between. Such a taxon (usually a species) is said to have a ''cosmopolitan'' distribution, or exhibit cosmopolitanism, as a species; another example, the rock dove (commonly referred to as a ' pigeon'), in addition to having been bred domestically for centuries, now occurs in most urban areas around the world. The extreme opposite of a cosmopolitan species is an endemic (native) species, or one foun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thallus
Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entire body of a multicellular non-moving organism in which there is no organization of the tissues into organs. Many of these organisms were previously known as the thallophytes, a polyphyletic group of distantly related organisms. An organism or structure resembling a thallus is called thalloid, thalloidal, thalliform, thalline, or thallose. Even though thalli do not have organized and distinct parts ( leaves, roots, and stems) as do the vascular plants, they may have analogous structures that resemble their vascular "equivalents". The analogous structures have similar function or macroscopic structure, but different microscopic structure; for example, no thallus has vascular tissue. In exceptional cases such as the Lemnoideae, where th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. The photons of ultraviolet have greater energy than those of visible light, from about 3.1 to 12 electron volts, around the minimum energy required to ionize atoms. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack sufficient energy, it can induce chemical reactions and cause many substances to glow or fluoresce. Many practical applications, including chemical and biological effects, are derived from the way that UV radiation can interact with organic molecules. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thylakoids
Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana (singular: ''granum''). Grana are connected by intergranal or stromal thylakoids, which join granum stacks together as a single functional compartment. In thylakoid membranes, chlorophyll pigments are found in packets called quantasomes. Each quantasome contains 230 to 250 chlorophyll molecules. Etymology The word ''Thylakoid'' comes from the Greek word ''thylakos'' or ''θύλακος'', meaning "sac" or "pouch". Thus, ''thylakoid'' means "sac-like" or "pouch-like". Structure Thylakoids are membrane-bound structures embedded in the chloroplast stroma. A stack of thylakoids is called a granum and resembles a stack of coins. Membrane The thylakoid membrane is the site of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosynthesis
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabolism. ''Photosynthesis'' usually refers to oxygenic photosynthesis, a process that produces oxygen. Photosynthetic organisms store the chemical energy so produced within intracellular organic compounds (compounds containing carbon) like sugars, glycogen, cellulose and starches. To use this stored chemical energy, an organism's cells metabolize the organic compounds through cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth. Some bacteria also perform anoxygenic photosynthesis, which uses bacteriochlorophyll to split hydrogen sulfide as a reductant instead of water, p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substrate (biology)
In biology, a substrate is the surface on which an organism (such as a plant, fungus, or animal) lives. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock (its substrate) can be itself a substrate for an animal that lives on top of the algae. Inert substrates are used as growing support materials in the hydroponic cultivation of plants. In biology substrates are often activated by the nanoscopic process of substrate presentation. In agriculture and horticulture * Cellulose substrate * Expanded clay aggregate (LECA) * Rock wool * Potting soil * Soil In animal biotechnology Requirements for animal cell and tissue culture Requirements for animal cell and tissue culture are the same as described for plant cell, tissue and organ culture (In Vitro Culture Techniques: The Biotechnological Principles). Desirable requirements are (i) air conditioning of a room, (ii) hot room with temperature recorder, (iii) microsc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Fixation
Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen fixation or ''diazotrophy'' is catalyzed by enzymes called nitrogenases. These enzyme complexes are encoded by the Nif gene, ''Nif'' genes (or ''Nif'' homologs) and contain iron, often with a second metal (usually molybdenum, but sometimes vanadium). Some nitrogen-fixing bacteria have symbiotic relationships with plants, especially legumes, mosses and aquatic ferns such as ''Azolla''. Looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. Nitrogen fixation occurs between some termites and fungus, fungi. It occurs naturally in the air by means of NOx, NOx production by lightning. Fixed nitrogen is essential to life on Earth. Organic compounds such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brackish Water
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuary, estuaries, or it may occur in brackish Fossil water, fossil aquifers. The word comes from the Middle Dutch root '':wikt:brak#Dutch, brak''. Certain human activities can produce brackish water, in particular civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming. Brackish water is also the primary waste product of the Osmotic power, salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it can be damaging to the environment (see article on shrimp farming, shrimp farms). Technically, brackish water contains between 0.5 and 30 grams of salt per litre—more ofte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nostoc Commune
''Nostoc commune'' is a species of cyanobacterium in the family Nostocaceae. Common names include star jelly, witch's butter, mare's eggs. It is the type species of the genus ''Nostoc'' and is cosmopolitan in distribution. Description ''Nostoc commune'' is a colonial species of cyanobacterium. It initially forms a small, hollow gelatinous globule which grows and becomes leathery, flattened and convoluted, forming a gelatinous mass with other colonies growing nearby. Inside the thin sheath are numerous unbranched hair-like structures called trichomes formed of short cells in a string. The cells are bacteria and thus have no nucleus nor internal membrane system. To multiply, they form two new cells when they divide by binary fission. Along the trichomes, larger specialist nitrogen-fixing cells called heterocysts occur between the ordinary cells. When wet, ''Nostoc commune'' is bluish-green, olive green or brown but in dry conditions it becomes an inconspicuous, crisp brownish m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterocyst
Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as ''Nostoc'', ''Cylindrospermum'', and '' Anabaena''. They fix nitrogen from dinitrogen (N2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. Nitrogenase is inactivated by oxygen, so the heterocyst must create a microanaerobic environment. The heterocysts' unique structure and physiology require a global change in gene expression. For example, heterocysts: * produce three additional cell walls, including one of glycolipid that forms a hydrophobic barrier to oxygen * produce nitrogenase and other proteins involved in nitrogen fixation * degrade photosystem II, which produces oxygen * up-regulate glycolytic enzymes * produce proteins that scavenge any remaining oxygen * contain polar plugs composed of cyanophycin which slows down cell-to-cell diffusion Cyanobacteria usu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
