Allelopathy phytochemicals

Chou, C.H. The role of allelopathy in phytochemical ecology. In Phytochemical Ecology Allelochemicals, Mycotoxins and Insect Pheromones and Allomones. Chou C.H. and Waller, GR. eds. Taipei, Taiwan Institute Botanica Academia Senica, 1989. 

Belz RG (2007) Allelopathy in crop/weed interactions - an update. Pest Manag Sci 63 308-326 Belz RG (2008) Stimulation versus inhibition - bioactivity of parthenin, a phytochemical from Parthenium hysterophorus L. Int Dose-Response Soc 6 80-96 Belz RG, Vehni ED, Duke SO (2007) Dose/response relationships in allelopathy research. In Fujii Y, Hiradate S (eds) Allelopathy new concepts and methodologies. Science Publishers, Enfield, NH, pp 3-29... 

Fig. 2 Functions of phytochemicals in plant growth and development. Phytoohemicals play multiple functions in plant growth and development, including pollen tube growth elongation (a), seed coat imposed dormancy reinforcement (b), modulation of lignin biosynthesis (c), regulation of auxin polar transport (d), shoot/root gravitropic responses (e), root nodulation (f) and allelopathy (g)...

Phytochemicals often provide a selective advantage to plants, for example by eliminating the competition by other species, in a process that is generally included within the broader context of allelopathy [47,48]. Allelochemicals released to the rizosphere, for example as root exudates or by decaying leaf tissues, or accumulating in the aerial space as volatile emissions, have been proposed to play an important... 

Abstract All plants produce compounds that are phytotoxic to another plant species at some concentration. In some cases, these compounds function, at least in part, in plant/plant interactions, where a phytotoxin donor plant adversely affects a target plant, resulting in an advantage for the donor plant. This review discusses how such an allelochemical role of a phytotoxin can be proven and provides examples of some of the more studied phytochemicals that have been implicated in allelopathy. These include artemisinin, cineoles, P-triketones, catechin, sorgoleone, juglone and related quinones, rice allelochemicals, benzoxazinoids, common phenolic acids, l-DOPA, and m-tyrosine. Mechanisms of avoiding autotoxicity in the donor species are also discussed. 

The question of how one proves allelopathy has been somewhat controversial because so few published studies even come close to considering all of the parameters mentioned above. The literature of allelopathy has many papers that define phytotoxic phytochemicals as allelo-chemicals. Most of these papers do not consider the activity of the compound(s) in soil or the actual concentration or availability of the compound that one might expect in soil in a field... 

Allelopathy may be invoked with confidence when soil concentrations of an allelochemical are at or above levels applied to soil that cause phytotoxicity. When concentrations are below such levels, allelopathy may still be taking place due to the continuous input of the compounds by the producing plant. This would be very difficult to imitate by exogenous application of the compounds. Furthermore, some have invoked synergism between natural phytotoxins to support the view that weakly phytotoxic phytochemicals are allelochemicals (e.g. [13]), but others have disputed such claims (e.g. [14,15]). This topic is discussed in more detail in the Section on Common Phenolic Acids. 

Ehike, S.O. et al. (1999) Tissue localization and potential uses of phytochemicals with biological activity. In Recent advances in allelopathy Vol. 1 (Macias, F.A. et al., eds). Servicio e Publicaciones-Univ. CMiz, Spain, pp. 211 218... 

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