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The biochemical interactions among all types of plants, including microorganisms. The term is usually interpreted as the detrimental influence of one plant upon another but is used more and more, as intended originally, to encompass both detrimental and beneficial interactions. At least two forms of allelopathy are distinguished: (1) the production and release of an allelochemical by one species inhibiting the growth of only other adjacent species, which may confer competitive advantage for the allelopathic species; and (2) autoallelopathy, in which both the species producing the allelochemical and unrelated species are indiscriminately affected. The term allelopathy, frequently restricted to interactions among higher plants, is now applied to interactions among plants from all divisions, including algae. Even interactions between plants and herbivorous insects or nematodes in which plant substances attract, repel, deter, or retard the growth of attacking insects or nematodes are considered to be allelopathic. Interactions between soil microorganisms and plants are important in allelopathy. Fungi and bacteria may produce and release inhibitors or promoters. Some bacteria enhance plant growth through fixing nitrogen, others through providing phosphorus. The activity of nitrogen-fixing bacteria may be affected by allelochemicals, and this effect in turn may influence ecological patterns. The rhizosphere must be considered the main site for allelopathic interactions.

Allelopathy is clearly distinguished from competition: In allelopathy a chemical is introduced by the plant into the environment, whereas in competition the plant removes or reduces such environmental components as minerals, water, space, gas exchange, and light. In the field, both allelopathy and competition usually act simultaneously.

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the effect of plants on one another as a result of their secretion of various substances. Four groups of such substances are known. Substances of two of the groups are formed by microorganisms: antibiotics, which suppress the vital activity of other organisms, and “maras-mines” (wilting substances), which act on higher plants. Substances of the two other groups are secreted by higher plants: phytoncides, which suppress the vital activity of microorganisms, and cholines, which retard the growth of higher plants. Sometimes a positive influence is observed by one plant upon another, which is particularly important in agrophytocenoses. The phenomenon of allelopathy must be taken into consideration in growing agricultural plants (including crop rotation and mixed sowings).


Grodzinskii, A. M. Allelopatiia v zhizni rastenii i ikh soobshchestv. Kiev, 1965.
Fiziologo-biokhimicheskie osnovy vzaimnogo vliianiia rastenii v fitotsenoze. Moscow, 1966.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(plasma physics)
The harmful effect of one plant or microorganism on another owing to the release of secondary metabolic products into the environment.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The results on the allelopathic effect of leaf and bark (1%, 2%, and 5%) leachates of Ficus subincisa, Bauhinia purpurea, and Toona hexandra on the germination of test crops are shown in Figs 1 and 2.
NO BULL'S-EYE Scientists haven't yet hit the target in developing allelopathic weed fighters.
This information is useful for plant breeding purposes, because a cultivar with high allelochemicals content such as Athinaida is a good candidate to enhance the allelopathic potential of other desirable barley cultivars through crossing or other genetic manipulation.
An allelopathic effect claimed for litter of some species of Juniperus (Jameson 1970a; Jameson 1970b; Whittaker & Feeney 1971; Everett et al.
Hulugalle NR, Entwistle PC, Roberts G, Finlay LA (1998b) Allelopathic behaviour of grain legumes in cotton-based farming systems.
Allelopathic potential of diffuse knapweed (Centaurea diffusa) extracts.
While the allelopathic properties of yellow mustard made it effective in suppressing weeds, yellow mustard may pose a greater risk of crop yield reduction than smother plant species that suppress weeds primarily through resource competition.
Zahir said he along with his team developed the technology and prepared a Bioherbicide containing Allelopathic Bacteria for Bio-control of Weeds of Wheat.
Allelopathic effects may also interact with competition for resources between some Amaranthus species and the crop in which they are growing (Connick et al., 1987; Bradow & Connick, 1988; Menges, 1988).
PESHAWAR -- Parthenium hysterophorus, an invasive weed specie commonly known as famine plant which damages crops production, livestock and human health due to its allelopathic (toxin releasing plants) nature, is fast spreading in Khyber Pakhtunkhwa (KP).
Among other invading plants, Prosopis juliflora (Kabuli Kekar- Kabul Acacia) has allelopathic properties, and Eucalyptus was known to transpire huge amounts of water and deplete the soil of its nutrient elements, it added.