Abstract
Plant-plant interference is the combined effect of allelopathy, resource competition, and many other factors. Separating allelopathy from resource competition is almost impossible in natural systems but it is important to evaluate the relative contribution of each of the two mechanisms on plant interference. Research on allelopathy in natural and cultivated plant communities has been hindered in the absence of a reliable method that can separate allelopathic effect from resource competition. In this paper, the interactions between allelopathic rice accession PI312777, non-allelopathic rice accession Lemont and barnyardgrass were explored respectively by using a target (rice)-neighbor (barnyardgrass) mixed-culture in hydroponic system. The relative competitive intensity (RCI), the relative neighbor effect (RNE) and the competitive ratio (CR) were used to quantify the intensity of competition between each of the two different potentially allelopathic rice accessions and barnyardgrass. Use of hydroponic culture system enabled us to exclude any uncontrolled factors that might operate in the soil and we were able to separate allelopathy from resource competition between each rice accession and barnyardgrass. The RCI and RNE values showed that the plant-plant interaction was positive (facilitation) for PI312777 but that was negative (competition) for Lemont and barnyardgrass in rice/barnyardgrass mixed-cultures. The CR values showed that one PI312777 plant was more competitive than 2 barnyardgrass plants. The allelopathic effects of PI312777 were much more intense than the resource competition in rice/barnyardgrass mixed cultures. The reverse was true for Lemont. These results demonstrate that the allelopathic effect of PI312777 was predominant in rice/barnyardgrass mixed-cultures. The most significant result of our study is the discovery of an experimental design, target-neighbor mixed-culture in combination with competition indices, can successfully separate allelopathic effects from competition.
Highlights
Plants can affect neighboring plants by releasing chemicals into the environment
Putnam and Duke later suggested that allelopathy can be separated from other mechanisms of plant interference in that any detrimental effect is exerted through the release of a chemical by the donor [5]
The root length, plant height, and plant dry weight of BYG were significantly decreased in rice/BYG mixed-cultures relative to controls
Summary
Plants can affect neighboring plants by releasing chemicals into the environment. The Austrian plant physiologist Hans Molish named this phenomenon, ‘‘allelopathy’’ in 1937. According to Mallik, the mainstream ecologists practically ignored research on allelopathy, based on the argument that in most allelopathy research the influence of other major factors such as resource competition, soil chemical and biological properties are not considered and successfully eliminated to demonstrate the effect of allelopathy [2] This is partly due to a lack of reliable techniques that can separate allelopathic influences from other forms of plant interference, and partly due to the complex nature of allelopathic effects under natural conditions. Rice [21] defined allelopathy as any direct or indirect effect by one plant (including microorganisms) on another through production of chemical compounds that escape into the environment This definition has been modified by the International Allelopathy Society to – any process involving secondary metabolites produced by plants, algae, bacteria, or fungi that influence the growth and development of biological and agricultural systems [22]. We demonstrate that by excluding uncontrolled soil factors this approach can separate the effects of allelopathy from resource competition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
