Autotoxicity is a biological phenomenon whereby a species inhibits growth or reproduction of members of that same species through the production of chemicals that are released into the environment. It is related to allelopathy but is technically different: autotoxicity means self-toxicity, and allelopathic effects refer to the effects of chemical compounds from one species on another after release into the environment; also, autotoxic effects are always inhibitory, whereas allelopathic effects are not necessarily inhibitory - they may stimulate other organisms.
This mechanism will result in reduced competition between members of the same species. Inhibition on the growth of other plants will increase the availability of nutrients.
In cultivation, autotoxicity can make it difficult or impossible to grow the same species after harvest of a crop. For example, this is known in alfalfa and the tree Cunninghamia lanceolata Other species displaying autotoxicity include the rush Juncus effusus and the grass Lolium rigidum.
Autotoxicity in alfalfa is produced from the first seeding of the plant. The plant emits a chemical or chemicals into the soil that reduce the effectiveness of further alfalfa seedings. Studies show that the chemical is extractable from fresh alfalfa, is water-soluble, reduces germination, and prevents root growth. Some believe that a chemical called medicarpin is responsible for autotoxicity. Roots of affected plants can be swollen, curled, discolored, and lack root hairs. Lack of root hairs reduces the plants ability to gather nutrients and absorb water. Crop rotation is used to counteract autotoxicity in alfalfa.
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- Understanding Autotoxicity in Alfalfa, John Jennings, Extension Forage Specialist, University of Arkansas Cooperative Extension Service
- Alfalfa Autotoxicity, Joel Bagg, Forage Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs, March 2001