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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, it is a type of interference competition but it is technically different: autotoxicity contributes to intraspecific competition, whereas allelopathic effects refer to interspecific competition. Furthermore, autotoxic effects are always inhibitory, whereas allelopathic effects are not necessarily inhibitory–they may stimulate other organisms.[1][2]

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[3] and the tree Cunninghamia lanceolata[4] Other species displaying autotoxicity include the rush Juncus effusus[5] and the grass Lolium rigidum.[6]

In alfalfa[edit]

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.[7] 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.[8] Crop rotation is used to counteract autotoxicity in alfalfa.


  1. ^ Keating, K.I. (1999). "Allelopathy: principles, procedures, processes, and promises for biological control". Advances in Agronomy. 67: 199.
  2. ^ Pielou, E.C. (1974). Population and community ecology : principles and methods (4th ed.). New York: Gordon and Breach. p. 164. ISBN 9780677035802. Retrieved 8 September 2017.
  3. ^ Chon, Su; Nelson, Cj; Coutts, Jh (Nov 2003), "Physiological assessment and path coefficient analysis to improve evaluation of alfalfa autotoxicity", Journal of Chemical Ecology, 29 (11): 2413–24, doi:10.1023/A:1026345515162, ISSN 0098-0331, PMID 14682523
  4. ^ Kong, Ch; Chen, Lc; Xu, Xh; Wang, P; Wang, Sl (Dec 2008), "Allelochemicals and activities in a replanted Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) tree ecosystem", Journal of Agricultural and Food Chemistry, 56 (24): 11734–9, doi:10.1021/jf802666p, ISSN 0021-8561, PMID 19053367
  5. ^ Ervin, Gn; Wetzel, Rg (Jun 2000), "Allelochemical autotoxicity in the emergent wetland macrophyte Juncus effusus (Juncaceae)" (Free full text), American Journal of Botany, 87 (6): 853–860, doi:10.2307/2656893, ISSN 0002-9122, JSTOR 2656893, PMID 10860916
  6. ^ Canals, Rm; Emeterio, Ls; Peralta, J (Aug 2005), "Autotoxicity in Lolium rigidum: analyzing the role of chemically mediated interactions in annual plant populations", Journal of Theoretical Biology, 235 (3): 402–7, doi:10.1016/j.jtbi.2005.01.020, ISSN 0022-5193, PMID 15882702
  7. ^ Understanding Autotoxicity in Alfalfa Archived 2011-06-14 at the Wayback Machine, John Jennings, Extension Forage Specialist, University of Arkansas Cooperative Extension Service
  8. ^ Alfalfa Autotoxicity, Joel Bagg, Forage Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs, March 2001