Non-trophic interactions: Allelopathy.

Many plants release allelopathic chemical compounds into their surrounding that mediate allelopathic interactions. In natural ecosystems, these allelochemicals act indirectly by influencing abiotic components of the ecosystem, e.g., nutrient cycling, organic matter dynamics and soil nutrient availability, and can also alter biotic ecology by affecting soil microbes and plant pathogens. In managed ecosystems, allelopathy may directly affect other crops when grown in various management systems, through autotoxic effects, soil sickness or supressing various weed and pest species. Thus allelopathy plays a significant role in the agroecosystems, forest plantations and agroforestry systems altering competitive interactions between plant species in the community and affecting crop yield. These interactions are mostly deleterious to the receiver plants but provide a selective advantage to the donor. The research and development of allelopathic research is of extreme importance for the improvement of agriculture, forestry and the global environment, because allelopathic interactions can also play a major role in the competitive success of invasive/exotic and native weeds, and allelopathic crops which disturb agricultural practices and cause environmental degradation. This chapter reviews the latest development in our understanding of allelopathy in promoting and restricting plant growth and the ways in which our knowledge can be used in sustainable management of natural and managed ecosystems.