Chemistry and Mechanisms of Allelopathic Interactions

Abstract

Allelopathy, originally defined as chemically elicited interactions between plants or fungi, is mediated by many types of compounds with different sites and modes of biochemical action. Although it is possible to measure a generalized effect, it is unlikely that deeper insight into the basic mechanisms of of this phenomenon will be obtained until problems are more clearly and specifically delineated. Future work should include identification of the compounds found in specific interactions and their evaluation in bioassay systems that use organisms actually involved in the response. A broader range of compounds and test organisms must be considered, and the biochemical sites and mechanisms of interaction must be evaluated, even for compounds that appear to be inactive. Once active compounds have been identified, their release, movement, uptake, and effects on source and target species in the allelopathic system should be examined. The effects of plant density require additional investigation. Studies in which plants are grown in various combinations and ratios can ultimately provide information about the major sources of allelopathic interaction in communities, the role of allelopathy in succession, and the nature and extent of coadaptation of organisms. Understanding the role of allelopathy in succession will require information about the chemistry and biology of interactions, and a better understanding of the ecological factors involved. Agricultural systems can supply much needed information, as they are similar to natural systems but usually are simpler and better defined. In turn, a better understanding of allelopathy is important in many phases of modern agriculture, especially in the tropics. By attacking allelopathic interactions at several organizational levels, the effects collectively known as allelopathy can be understood, even in complex natural communities. Major advancement in understanding allelopathy will be accomplished only by the combined effort of investigators from many disciplines.

Germination and growth inhibitory effects of Hypericum myrianthum and H. polyanthemum extracts on Lactuca sativa L.

“…Some of these substances may be associated with allelopathy, and play an important role in chemical interactions in natural plant communities (Einhelling, 1996, Seigler, 1996, Dayan et al, 2000. In fact, a number of plants have been reported to possess inhibitory effects on the growth and population of neighboring or succession plants by releasing allelopathic substances into the soil (Rice, 1984, Inderjit, 1996, Narwal, 1999.…”

Growth Response of Seedlings of Zea Mays (L.) to Aqueous Extract of Lycopodium Clavatum (L.)

“…Allelopathic behaviour can best be described as direct or indirect effects of compound resulting from organism, which may have inhibitory or stimulatory effects on the same or other organisms. In this process, synthesis of biologically active molecules produced by plant and their residue may be converted to other forms and influenced the growth of similar or non-similar plants [7]. The earliest writings on this topic are attributed to Theophrastus (ca.300 B.C), a successor of Aristotle who noticed the harmful effects of cabbage on a vine and suggested that such effects were caused by odours from the cabbage plants.…”

Allelopathy: driving mechanisms governing its activity in agriculture

“…These compounds are produced mainly as a result of the secondary metabolism of plants and microorganisms (bacteria, viruses and fungi) and can influence several processes in ecosystems and agroecosystems (Rizvi et al 1992;Seigler 1996;Olofsdotter et al 2002). Allelochemicals can lead to different mechanisms of action in plants.…”