Allelopathy, phenomenon

In summary, it is expected that, for allelopathy studies, the analytic power of multi-stage chromatography-mass spectrometry techniques will generate much useful qualitative and quantitative data, thereby helping to unravel some of the remaining mysteries of the allelopathy phenomenon. 

In many ecosystems, plants tend to pattern themselves as pure stands or as individuals spaced in rather specific densities or configurations. Many desert species show obvious zones of inhibition around which few, if any, alien species are able to invade. These patterns often cannot be adequately explained by competition alone, and are probably caused by a combination of factors including allelopathy. The phenomenon happens with herbaceous plants as well as woody shrubs and trees. 

The latter problems are of particular interest to chemists, who should devise appropriate methods for resolving the complexity of chemicals, properly identifying them and finally determining their exact composition and makeup. The participation of chemists is needed to verify the concept of allelopathy as a concentration-dependent phenomenon. They should help to reconstitute the chemical composition as it was found in the original and isolated plant samples. This systematic approach leads to verification of the concept as well as to proper assessment of the initial observation with crude extracts, and to final application to the field situation. Once the concept is proven, same simulation experiments need to be performed to maximize the allelopathic effect (toxin action). The concentration of the toxic chemicals is varied to where the threshold levels of chemicals prove to be involved in the exhibition of allelopathy under field conditions. 

The term allelopathy, when first proposed by Molisch (1 ), referred to either the beneficial or detrimental interaction between all types of plants and microorganisms. As presently used, this definition is generally accepted. Since 1970 a concerted effort has been made to understand the phenomenon of allelopathic interaction. The many interpretations resulting from these studies are well documented in the literature (2-4). An area currently receiving considerable attention is the allelopathic effect resulting from weed-crop and weed-weed interactions (2, 5-7). One study conducted by Wilson and Rice (7) showed that the common sunflower, Helianthus annuus L., possessed allelopathic properties. Realizing the inherent potential... 

Shapiro, H. M. (2003). Practical Flow Cytometery. Wiley-Liss, New YorkUSA Sukhada, K.D. and Jayachandra (1980a). Pollen allelopathy - a new phenomenon. 

Pollen allelopathy is phenomenon when pollen chemicals (e.g., phenols, terpenoids, sesquiterpene lactones, etc.) inhibit sexual reproduction in heterospecific individuals due to influencing of fertilization (Murphy 1992). The phenomenon includes excretion of signaling compounds from the donor cell (pollens, pistil stigma), recognition of a specific signal, transmission of information (pollen), and the development of a characteristic response in the acceptor cell. The possible mechanism of the effect was described in Roshchina (2001). 

Newly investigated pollen allelopathy could effectively reduce the reproductive ability of wind pollination of annual weeds. Pollen of allelopathic species could be artificially dusted on the stigmatic surface of other plants. This phenomenon needs study and field testing yet. 

At the end of the 1950s allelopathy was already well known among botanists and plant physiologists, but it was considered rather a minor and rare phenomenon that had no great ecological importance. We have screened many plant exudates, and reached the conclusion that many species are allelopathically active indeed, practically any plant under certain conditions so affects otiier plants... 

Although the phenomenon of allelopathy was first described by De Candolle (1), Pliny the Elder writing in the first century A.D. in his Naturalis Historia described the failure of certain plants to grow in the shade of Juglans regia. In addition nearly every society has had folklore about the effects of one plant upon another. 

Phenolics may influence competition among plants, a phenomenon called allelopathy. A series of experiments in both the field and the laboratory have indicated a role for a number of phenolic derivatives (hydroquinone, hydroxybenzoates and hydroxycinnamates) as allelopathic agents. These are chemicals excreted by the plant, which may be autotoxic or affect the growth of other plants in the environment [6,7]. 

Initially, most of the work in allelopathy was observational, and the science was chided by purists as being clumsy and somewhat lacking in hard content and proof. But in recent years, some of the chemical causes and effects for the allelopathic phenomenon have begun to take form. Essentially, this was the substance of Recent Advances in Allelopathy. Volume 1. A Science for the Future. (Eds. F.A. Macias, J.C.G. Galindo, J.M.G. Molinillo and H.G. Cutler. University of Cadiz Press. 1999). Indeed, that publication was a mix of both observational and chemical allelopathy, and it emanated from the First Symposium of the International Allelopathy Society (IAS), held in Cadiz, Spain, in September 1996. Essentially, the present work, Allelopathy Chemistry and Mode of Action of Allelochemicals is Volume II in the continuing saga of allelopathy and the title is self explanatory. 

At least 50 alkaloids have been demonstrated to inhibit the germination or the growth of seedlings. This phenomenon, referred to as allelopathy, is important in competition between plants and is frequently directed against seedlings by mature plants of the same species.37 A diversity of alkaloids, including quinine,... 

Compounds derived from shikimic acid pathways and especially phenolic substances have been encountered in a number of studies of chemical interactions between plants. This chemical warfare is often called allelopathy. Although much controversy surrounds the importance of this phenomenon, allelopathy seems to be most important in seasonally dry habitats. 

The already described phenomenon of the effects of one plant on the other, which in physiology plays and will play an important role, deserves to be described by a special term. I propose for it the word Allelopathy , derived from two Greek Words . .. (allelon) means reciprocal, mutual, among each other, and. .. (pathos) means grief, sorrow, or that which happens to one. 

Most scientists consider allelopathy to be the phenomenon of chemical warfare between plants, although some have defined it much more broadly (e.g. [1]), in some cases encom-... 

Fomsgaard, I.S. (2006) Chemical ecology in 131. wheat plant-pest interactions. How the nse of modem techniques and a multidisciplinary approach can throw new light on a well-known phenomenon Allelopathy. J. Agric. 132. Food Chem. 54, 987 990... 

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