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Glossary of Terms Aeroponics: a variation of hydroponics that involves the misting of plant roots with nutrient solution. Allele: different forms of the same gene; allele "A" may produce a tall plant, while allele "a" gives a short plant. Anther: part at the top of the male flower that produces the pollen. Aquaponics: the integration of aquaculture (the raising of marine animals, such as fish) with hydroponics; the waste products from the fish are treated and then used to fertilize hydroponically growing plants. Bacterial soft rot. See Botrytis. Bolting: for a plant to prematurely begin the development of a flowering stalk and, subsequently, seed. Botrytis: any of several fungal diseases that afflict plants; commonly called bacterial soft rot or gray mold. Capillary action: when the surface of a liquid is in conact with a solid, the liquid is elevated or depressed depending upon the relative attraction of the molecules of the liquid for each other or for those of the solid. This is similar to how plants seemingly defy gravity when they transport liquid from the roots upward through the plant. Chlorophyll: the green material in plants that is created in the presence of light and is instrumental in photosynthesis. Cladosporium: any of several fungal diseases that afflict plants; commonly called leaf mold. Closed system: a hydroponic system, like nutrient film technique (NFT) systems, that recirculates the nutrient solution. Conductivity: the scale, described as electrical conductivity (EC) or conductivity factor (CF), that is used to measure the strength of nutrient solution. Cross-pollination: transferring pollen from the flowers of one plant of a species to the stigma of another plant of the same species. Deficiency. See mineral deficiency. Dioecious: varieties or species with male and female flowers on separate plants. Dry rot. See Fusarium. Electrical conductivity. See conductivity. F1, F2, F3, etc.: the F1 generation is the result of crossing two different varieties; a cross of two F1 plants produces F2 seed; and so on. Filament: see stalk. Fusarium: any of several fungal diseases that afflict plants; commonly called dry rot or wilt. Germination: the activation of a seed causing it to start to grow; also the production of a pollen tube by a pollen grain Gray mold. See Botrytis. Growing medium: materials that are sometimes used in hydroponic growing to support the plant's roots and, sometimes, to hold nutrient. Insects: a variety of insects attack plants. These include aphids, caterpillars, cutworms, fungus gnats, leaf miners, nematodes, spider mites, thrips, and whiteflies. Leaf mold. See Cladosporium. Macronutrients: the major minerals that are used by plants in large amounts, consisting of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg). Micronutrients: the minor minerals that are used by plants in small amounts, consisting of boron (B), copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn). Mineral deficiency: when a plant is not receiving a required nutrient--at all or in an insufficient amount--a disorder will result. Monoecious: varieties or species with separate male and female flowers on each plant. Nutrient solution: minerals dissolved in water that are used to feed hydroponically grown plants. Osmosis: the flow or diffusion that takes place through a semipermeable membrane typically separating a solvent and a solution that strives to bring about a condition of equilibrium. Parts per million (ppm): a ratio figure that represents the amount of one substance that is in one million parts of another substance; commonly used to describe the relative concentrations of nutrient solutions. pH: a measurement of a nutrient solution's relative concentration of positive hydrogen ions: a pH of 7 is considered neutral; below 7 is called acidic; above 7 is called alkaline. Photosynthesis: the formation of carbohydrates from carbon dioxide (CO2) and a source of hydrogen (H)--such as water--in chlorophyll-containing cells exposed to light involving a photochemical release of oxygen through the decomposition of water. Pistil: the entire female section of the flower, including the eggs, ovary, style, and stigma. Pollen: the mass of microspores in a seed plant that usually appears as a fine dust and is the agent of pollination. Pollination: the transfer of pollen from the male part of a flower (stamen) to the female part of a flower (the style and stigma). Reverse osmosis: the process of removing minerals from water, which is forced by pressure through a differentially permeable membrane, filtering out the minerals; can happen when growers accidentally apply too strong of a nutrient to a plant's roots, leeching life out of the plant. Stalk: on a male flower, the portion of the stamen that supports the anther. Stamen: the basic part of the male flower that includes the stalk (or filament), anther, and pollen. Sterilization: the act of rendering something free from living cells. In hydroponics it is essential that all materials (especially any growing medium) used are sterile to avoid contaminating the hydroponic system. Steam and chemical agents are often used in this process. Stigma: the surface at the end of the pistil on a female flower where pollen lands and germinates. Style: the part of a female flower that supports the stigma. Verticillium: any of several fungal diseases that afflict plants; commonly called wilt. See also Fusarium. Wick: woven fiber used in some hydroponic systems to draw nutrient to a plant's roots through capillary action. Wilt. See Fusarium and Verticillium. Several texts were useful as resource materials while creating this glossary:
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