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Home >>Botany Dictionary >> Geotaxis - Golden Brown Algae
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Germination - The intake of water by a seed, spore etc., leading to an increase in metabolism and elongation, finally resulting in the formation of new tissue.
Germ Plasm - Said of the genetic material, especially that contained within the reproductive (germ) cells in an organism.
Germ Pore - A thin walled area on a spore wall, or pollen grain through which a germ-tube is produced.
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Germ Sporangium - A sporangium which is formed at the end of a germ-tube produced by a zygospore.
Germ Tube - (1) A tubular outgrowth, put out by a germinating spore, from which the thallus is developed by branching, or a germ sporangium is produced.
(2) A tube put out by a germinating pollen grain, carrying the male nuclei and growing down through the style.
Giant Ferns - Used for the members of order Marattiales of pteridophytes of Filicinae numbering about 100 species of 6 genera. They are large, fleshly tropical ferns. In most species, plant is a sporophyteand ahs a broad and short stem on which arise large, compound fronds having sporangia formed on abaxial surface of sporophylls that otherwise resemble normal sterile fronds.
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Gibberellic Acid (GA3) - The first of the plant growth substances gibberellins which was isolated from fungus Gibherella fujikuroi by Kurosawa that causes a disease of rice seedlings characterized by excessive elongation of shoots and leaves. Its basic structure, like other gibberellins, is having gibbane carbon skeleton. It is a terpenoid and is synthesized from mevalonic acid.
Gibberellins - A group of growth-promoting substances which occurred widely in plants. They increase rate of photosynthesis, e.g. increase cell-elongation, promote germinantion and flowering.
Gibbose, Gibbous - (1) Swollen, especially at one side. (2) Pouched.
(3) Convex above, and flattened below.
Gill - One ofthe vertical plates of mycelium which bear the hymenium of an agaric.
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Girdling - Said of the condition when a leaf trace arises on the opposite side of the stele from the leaf which it serves, and in reaching the leaf curves widely through the cortex.
Glabrous - A Surface that is smooth, but lacks haris or any type of projections.
Gland - An organ, or cell which is secreting a specific substances, sometimes surrounding a cavity.
Glans - A hard, dry, indehiscent fruit, having one or more seeds. It is derived from an inferior ovary, and more or less enclosed ina cupule.
Glaucous - Used for describing a surface having a waxy, grayish blue green bloom e.g., the leaves of rape or swede.
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Gleba - The mass of spore-producing tissue which forms in the fruiting bodies of such fungi as truffles, puffballs, earthstars, stickhorns etc. It is enclosed by the peridium.
Gley Horizon - A horizon in a soil which is characterized by the deposition of secondary hydrated ferric oxide.
Gley Soil - A soil developed under impeded drainage, and in consequence, is having a horizon of secondary hydrated ferric oxide. More generally, with a greenish-grey shiny horizon, which may have little iron.
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Gliadin - A storage potein, found particularly in wheat grains.
Gliding Bacteria - Used for bacteria of order Beggiatoales. They are unicellular or filamentous and move by gliding over the surface. Many are filamentous sulphur bacteria growing by oxidizing sulphides.
Glochid - A short hair, many of which are arising in tufts from the areoles of some cacti. It is a type of glochidium.
Glochidium - Hair like processes on the masses of microsporangia produced by Azolla. They serve for attachment to the macrosporangium.
Glucan - Any polysaccharide which is made up exclusively of glucose subunits e.g., starch and cellulose.
Gluconeogenesis - Used for the reactions of formation of glucose from various precursors e.g., pyruvates: certain amino acids and intermediates of Krebs' cycle. Most of the stages have been found to bereverse of glycolytic reactions except conversion of phosphoenol pyruvate to pyruvate and conversion of Fructose 1, 6-biphosphate to fructose 6-phosphate.
Glucoside - A glycoside in which the sugar is glucose, and which is formed from it on hydrolysis.
Glucose (dextrose, grape sugar). An aldolase sugar forming a 6-membered pyranose ring in solution. It is main fuel for respiration and basic substrate forming cellulose, starch and other carbohdrates. It is synthesized by photosynthsis in plants but also by other pathways.
Glucuronic Acid - The type of luronic acid which is derived from & glucose. It is a common constitiuent of gums and mucilages.
Glume - One of a pair of dry bracts, at the base of and enclosing the Spikelet of grasses.
Glutamic Acid Dehydrogenase - The enzyme catalysing ;the reversible reaction of a-ketoglutaric acid to glutamic acid.
Glutamine Synthetase - The enzyme catalysing the synthesis of glutamine from glutamic acid and ammonia.
Glutelins - A group of simple protiens that are insoluble in water,dilute salt solutions, 70% ethanol, but dissolve in dilute alkalis or acids.
Gluten - (I) A reserve protein which is found in plants.
(2) The sticky coating on the pilei of some agarics.
Glycolic Acid - A substrate which gets oxidized during photorespiration in C3 plants. It is formed by oxidation of ribulose bipholsphate to phosphoglyceric acid and phosphoglycolic acid and hydrolysis of phosphoglycolic acid then yields glycolic acid. It gets oxidized by molecular oxygen during photorespiration, catalyzed by glycolate oxidase to yield glyoxylic acid. This reaction takes place in peroxisomes and also produces H2O2.
Glycolipid (glycosyldiacylglycerol), Used for describing any of a group of acylglycerols having a carbohydrate group, usually a monodi-or trisaccharide or an amino sugar. These are major lipid constituents of chloroplasts.
Glycolysis (Embden-Meyerhof-Parnas pathway). Used for describing pathway in which glucose breaks down to pyruvic acid anaerobically. Glycolysis of one glucose molecule consumes 2 ATP and yields 4 ATP molecules.
Glycophytes - Used for describing plants that are sensitive to a high salt-concentration in the soil.
Glycoside - A compound which is formed by the combination of another molecule (ROH) with the H+ of an OH radicle of a sugar.
Glycoprotein - Used for describing a macromolecule consisting of a backbone of protein along which short disaccharide branches are attached at invervals.
Glyoxylate cycle (glyoxalate cycle). Used for describing a cyclic
metabolic path way involving TCA cycle intermediaries in which one melecule of succinic acid is formed by the combination of two molecules of accetyl CoA. Reactions differing from TCA cycle get catalyzed by isocitric lyase and malate synthetase respectively. No CO2 gets formed in the cycle and cycle allows formation of carbohydrate from fatty acides via succinate. Enzymes of the cycle are active in oil bearing seeds and in other fat metabolising tissues present in the plant. This cycle can take place in micro organisms but not in animals.
Glyoxylic Acid Cycle - A modification of the Citric Acid Cycle. It seems to be limited to tissues where fats are being rapidly consumed, e.g., the endosperm of germinating fatty seeds.
Glyoxysome - A microbody having 5 enzymes of glyoxylate cycle. Glyoxysome occur in cells of higher plants that utilize fat in this way e.g., endosperm or cotyledons of fat storing seeds. These also have an enzyme for catalyzing the decomposition of hydrogen peroxide to water and oxygen.
Golden Brown Algae - Used for discribing the members of division Chrysophyta. They usually consist of flagellate, uniceillar but some colonial and filamentous algae which usually have two golden-brown plastids in each cell and store food as fat or leucosin.
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