| toxin | <pharmacology> A poison, frequently used to refer specifically to a protein produced by some higher plants, certain animals and pathogenic bacteria, which is highly toxic for other living organisms. Such substances are differentiated from the simple chemical poisons and the vegetable alkaloids by their high molecular weight and antigenicity. Origin: Gr toxikon = arrow poison, from Gr. Toxikos = of or for a bow (18 Nov 1997) |
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| toxin spectrum | A figure in the form of a spectrum used by Ehrlich to represent the neutralizing power of antitoxin in the presence of toxin, toxone, etc. (05 Mar 2000) |
| erythrogenic toxin | <protein> Toxin produced by strains of Streptococcus pyogenes responsible for scarlet fever. Three antigenic variants of the toxin are known. It is a small protein that is complexed with hyaluronic acid and can intensify the effects of other toxins such as endotoxin and streptolysin O. (18 Nov 1997) |
| extracellular toxin | <protein> Toxin released from gram-positive and gram-negative bacteria as opposed to endotoxins that form part of the cell wall. Examples are cholera, pertussis and diphtheria toxins. Usually specific and highly toxic. (18 Nov 1997) |
| air plant | <botany> A plant deriving its sustenance from the air alone; an aerophyte. The "Florida moss" (Tillandsia), many tropical orchids, and most mosses and lichens are air plants. Those which are lodged upon trees, but not parasitic on them, are epiphytes. Source: Websters Dictionary (01 Mar 1998) |
| aquatic plant | <botany> Plants that must grow in water whether rooted in the mud or floating without anchorage, plants that must complete part or all of their life cycle in or near the water. (09 Oct 1997) |
| C3 plant | <plant biology> Plants that fix carbon dioxide in photosynthesis by the Calvin Benson cycle. The enzyme responsible for carbon dioxide fixation is RuDP carboxylase, whose products are compounds containing three carbon atoms. C3 plants are typical of temperate climates. Photorespiration in these plants is high. (07 Nov 1997) |
| C4 plant | <plant biology> Plants found principally in hot climates whose initial fixation of carbon dioxide in photosynthesis is by the HSK pathway. The enzyme responsible is PEP carboxylase, whose products contain four carbon atoms. Subsequently the carbon dioxide is released and re fixed by the Calvin Benson cycle. The presence of the HSK pathway permits efficient photosynthesis at high light intensities and low carbon dioxide concentrations. most species of this type have little or no photorespiration. (21 Mar 1998) |
| vascular plant | A plant which possesses a well-developed system of conducting tissue to transport water, mineral salts and sugars. (09 Oct 1997) |
| gene expression regulation, plant | Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in plants. (12 Dec 1998) |
| genes, plant | The hereditary material of plants. (12 Dec 1998) |
| genes, structural, plant | DNA sequences that code for RNA and for the proteins required for the enzymatic and structural function of plant cells. (12 Dec 1998) |
| genome, plant | The complete gene complement contained in a set of chromosomes in a plant. (12 Dec 1998) |
| RNA, plant | Ribonucleic acid in plants having regulatory and catalytic roles as well as involvement in protein synthesis. (12 Dec 1998) |
| photosynthetic reaction centre, plant | A system consisting of proteins and cofactors which facilitates light energy and electron transfer in plants. (12 Dec 1998) |