Absorption Active: movement of ions and water into the plant root as a result of metabolic processes by the root, frequently against an activity gradient. Passive: Movement of ions and water into the plant root as a result of diffusion along an activity gradient. See Adsorption. |
Acidity The activity of hydrogen ions in a solution. It is measured and expressed as a pH value. |
Adhesion Molecular attraction that holds the surfaces of two substances I contact, such as water and rock particles. |
Adsorption The bonding, usually temporary, of ions or compounds to the surfaces of a solid, such as a calcium ion held on the surface of a clay crystal or a humus particle, where it may be absorbed by a plant root. See Absorption |
Aeration The process by which air is introduced into a solution. Poorly aerated solutions usually contain a much higher percentage of carbon dioxide and a correspondingly lower percentage of oxygen. |
Aerobic Having molecular oxygen as a part of the environment. Growing only in the presence of molecular oxygen, as aerobic organisms. |
Aggregate Water-stable materials, which will not flake, crumble, or disintegrate easily. |
Algae Any of various primitive chlorophyll bearing plants found in water including seaweeds and kelp. |
Alkalinity The degree or intensity of alkalinity of a solution, expressed by a pH value greater than 7.0. |
Amendment Any substance added to a solution or soil that alters its properties. Examples are fertilizers, gypsum, lime, perlite, or compost. |
Amino acid Any of a group or organic compounds containing the amino groups (NH2) forming a part of the protein molecule. |
Anaerobic The absence of molecular oxygen. Growing in the absence of oxygen such as anaerobic bacteria. Biochemical processes occurring in the absence of oxygen. |
Atmosphere The ambient gases surrounding an object. As a reference to air conditions. A unit of pressure which at sea level is 1.013 bars or 76cm of mercury at 0 degrees C or 29.92 inches of mercury at 32-F or 14.696lbs per sq in. |
Bacteria Microscopic, unicelled or noncellular plants, causing fermentation and decomposition of organic matter and ranging from harmless or beneficial to those that cause disease. |
Buffers Stable solutions or compounds such as clays and carbonates and phosphates that enable solutions or soil to resist change in concentration of soluble ions (pH). Also a solution used to calibrate electronic pH meters. |
Carbohydrate Compound containing carbon, hydrogen and oxygen including sugars, starches and cellulose. |
Cation (cat-i-on) Positively charged ion; ion which, during electrolysis, is attracted to the cathode. Some common cations are calcium, magnesium, sodium, potassium, ammonium, and hydrogen. |
Cation Exchange The interchange between a cation in solution and another cation on the surface of any surface-active material, such as clay colloid organic colloid, or plant root surface. |
Chelate (kee-late) The formation of strong bonds between metals and organic compounds. Some are insoluble such as in soil humus. Those chelates used in fertilizers are soluble an help keep the nutrient metals like iron, zinc, manganese, and copper mobile in the solution, thus improving plant uptake. Derived from Latin to mean (claw-like). |
Chlorophyll The green nitrogenous matter contained in the chloroplasts of lants, essential in production of carbohydrates by phosynthesis. |
Chloroplast A flattened plant cell which is able to perform photosynthesis. |
Chlorosis A loss of normal green color of the plant. Colors may be uniform pale green, brown spotted, or yellowish over the entire leaf or only between the leaf veins. |
Cohesion Holding together; force holding a solid or liquid together, owing to attraction between like molecules; cohesion decreases with rise in temperature. |
Colloid A substance that, when suspended in water, diffuses not at all or very slowly through a semi permeable membrane, and usually has little influence on freezing point, boiling point, or osmotic pressure of the suspension; a substance in a state of fine subdivision with particles from 1 micron to 1 millimicron. |
Compost Organic residues or a mixture of organic residues and soil that have been piled and allowed to undergo biological decomposition. |
Defoliate To lose foliage (leaves), especially prematurely or as a result of disease. |
Elongation When a leaf flower, or limb grows in an abnormally stretched fashion. |
Fertilizer An organic or inorganic material with the properties of minerals required for plant metabolism. |
Foliar To apply to the foliage (leaf) surface, usually as a spray. |
Fungicide A chemical substance used to kill or control fungus growth. |
Gradient A rate of change in certain variable factors such as pressures or temperatures. |
Herbicide A chemical substance capable of killing plant materials, usually weeds. |
Hormone A cell product in plant fluids, which has a specific effect on other cells. |
Humus An amorphous organic substance nearly completely decomposed. |
Ion Atoms, groups of atoms, or compounds that are electrically charged as a result of the loss of cations or the gain of anions. |
Irrigation The manner in which water is artificially applied to an area. |
Leaching To be removed or dissolved by percolation of filtration. |
Lignin A complex organic polymer that is deposited within the cellulose of a plants cell walls during thickening to make the wall rigid. |
Macronutrient A chemical element necessary in large amounts (usually greater than 10 part per million in the plant) for the growth of plants, usually applied as fertilizer. Macro refers to quantity and not the essentiality of the element. |
Membrane A thin pliable sheet like layer of animal or vegetable tissue, serving to cover or line an organ or part, separate adjoining cavities, or connect adjacent structures. |
Metabolism The sum of the chemical reactions that occur within a living organism. |
Micronutrient A chemical element necessary in only extremely small amounts (less than 1 part per million in the plant) for the growth of plants. Micro refers to the amount used rather than to its essentiality. Examples are boron, chlorine, copper, iron, manganese, molybdenum, and zinc. |
Mycorrhiza Literally fungus root. The association, usually symbiotic, of specific fungi with the roots of specific higher plants. |
Necrotic The death and decay of plant tissue. |
Nematode An extremely small (.5-1.5mm long) nonsegmented worm. Some are parasitic and live on plant roots. |
Nitrification The biological oxidation of ammonium salts to nitrites and the further oxidation of nitrites to nitrates. |
Nitrogen Assimilation The incorporation of nitrogen compounds into cell substances by living organisms. |
Nodule A structure developed on the roots of most legumes and some other plants in response to the stimulus of root nodule bacteria. |
Nutrient balance An as yet undefined ratio among concentrations of nutrients essential for plant growth, which permits maximum growth rate and yield. An imbalance results when one or more nutrients are present in either deficient or excess supply. |
Organic The scientific definition or organic is any chemical compound containing carbon. A common interpretation is any substance derived from living organisms, plant or animal. |
Osmosis The diffusion of a fluid through a semi permeable membrane. Resulting in equalization of pressures on each side. |
Oxidation Combination with oxygen; addition of oxygen or other atom or group; removal of hydrogen or other atom or group. |
Pathogens Any disease producing bacterium or microorganism. |
Photon A quantum of radiant energy moving with the velocity of light and an energy proportional to its frequency. |
Photosynthesis The process by which plants form carbohydrates from carbon dioxide, inorganic salts, and water through the agency of sunlight acting upon chlorophyll. |
Precipitate To separate and settle a substance into solid form, previously held in a solution. |
Protein Any of a class of highly complex nitrogenous compounds originally synthesized by plants, and forming an essential constituent in the process of animal metabolism. |
Reduction The chemical process in which electrons are gained and the negative valence is increased. The process of depriving a compound of oxygen. |
Senescence The act of reaching maturity or growing old. |
Substrate Used casually to describe a root zone grow medium such as soil or potting mixes. A substance in which another substance is absorbed. |
Symbiotic Referring to the relationship of dissimilar organisms, which consort together in a mutual advantageous partnership. |
Transpiration The process by which water vapor released to the atmosphere, primarily through the leaf. |
