Separation of Allelopathy from Resource Competition Using Rice/Barnyardgrass Mixed-Cultures

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.

Allelopathic Effects of <i>Argemone mexicana</i> to Growth of Native Plant Species

“…Competitive ability of invasive species over native species is explained by various hypothesis which includes release from natural enemies that hold them in check and make them free to utilize their full competitive potential [3] [6], evolution of increased competitive ability [7] [8], phenotypic plasticity that helps invasive plants to adapt to novel environments and compete against native plants in recipient communities [9] and the production of allelopathic compounds [3] [4] [10]. Plants can affect neighbouring plants by producing and releasing chemicals into the environment [11]. The Austrian plant physiologist Hans Molish named this phenomenon, "allelopathy" in 1937.…”

De novo Assembly and Characterization of the Barnyardgrass (Echinochloa crus-galli) Transcriptome Using Next-Generation Pyrosequencing

“…is one of the main problematic grass weeds that grows along with important staple crops such as rice [1]. During cultivation even when the ratio of rice plants to barnyardgrass is 10∶1 rice biomass is reduced by 75% and yield by about 50% [2]. Many herbicides are being used to destroy barnyardgrass which in turn would improve rice production.…”

Allelopathic Effect of Aqueous Extract of Argemone mexicana L on Germination and Growth of Brachiaria dictyoneura L and Clitoria ternatea L

“…Production and release of allelopathic compounds (allelochemicals) by invasive species are factors that enhance its competitive ability over native species [4]. Plants can affect neighboring plants by releasing chemicals into the environment [5]. The Austrian plant physiologist Hans Molisch named this phenomenon "allelopathy" in 1937 [6].…”