Autotoxicity, meaning self-toxicity, is a biological phenomenon whereby a species inhibits growth or reproduction of other members of its same species through the production of chemicals released into the environment. Like

allelopathy Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have be ...

, it is a type of

interference competition Competition is an Biological interaction, interaction between organisms or species in which both require a Resource (biological), resource that is in Limiting factor, limited supply (such as food, water, or Territory (animal), territory). Competi ...

but it is technically different: autotoxicity contributes to

intraspecific competition Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to r ...

, whereas allelopathic effects refer to

interspecific competition Interspecific competition, in ecology, is a form of competition in which individuals of ''different'' species compete for the same resources in an ecosystem (e.g. food or living space). This can be contrasted with mutualism, a type of symbiosis. ...

. Furthermore, autotoxic effects are always inhibitory, whereas allelopathic effects are not necessarily inhibitory–they may stimulate other organisms. This mechanism will result in reduced exploitative competition between members of the same species and may contribute to natural thinning in established communities. Inhibition of the growth of young plants will increase the availability of nutrients to older, established plants. 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 Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as w ...

and the tree ''

Cunninghamia ''Cunninghamia'' is a genus of one or two living species of evergreen coniferous trees in the cypress family Cupressaceae. They are native to China, northern Vietnam and Laos, and perhaps also Cambodia. They may reach in height. In vernacular ...

lanceolata'' Other species displaying autotoxicity include the rush ''

Juncus effusus ''Juncus effusus'', with the common names common rush or soft rush, is a perennial herbaceous flowering plant species in the rush family Juncaceae. In North America, the common name soft rush also refers to '' Juncus interior''. Distribution ' ...

'' and the grass ''

Lolium rigidum ''Lolium rigidum'' is a species of annual grass. Common names by which it is known include annual ryegrass, a name also given to Italian ryegrass (''Lolium multiflorum''), rigid ryegrass, stiff darnel, Swiss ryegrass and Wimmera ryegrass. It is ...

''.

In alfalfa

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 Medicarpin is a pterocarpan, a derivative of isoflavonoids. Natural occurrences Medicarpin is found in ''Medicago truncatula'' and ''Swartzia madagascariensis''. It can also be found in ''Maackia amurensis'' cell cultures. The root nodule form ...

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.Alfalfa Autotoxicity
Joel Bagg, Forage Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs, March 2001

Crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...

is used to counteract autotoxicity in alfalfa.

References

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