The relative importance of allelopathy in interference: the effects of an invasive weed on a native bunchgrass

Abstract

The relative importance of allelopathy and resource competition in plant-plant interactions has been vigorously debated but seldom tested. We used activated carbon to manipulate the effects of root exudates of Centaurea maculosa, a noxious weed in much of western North America, on root elongation rates and growth of the native bunchgrass Festuca idahoensis in order to investigate the relative importance of allelopathy in the total interference of Centaurea. In root observation chambers, Festuca root elongation rates decreased to ≈50% of the control, beginning 4 days before contacting Centaurea roots in silica sand. However, when activated carbon, which has a high affinity for adsorbing to organic compounds, was added to the sand the effects of Centaurea roots on Festuca root elongation were reduced. In other experiments, Festuca plants were 50% smaller when grown with Centaurea than with conspecifics in pure silica sand. However, Festuca grown with Centaurea in mixtures of sand and activated carbon were 85% larger than Festuca grown with Centaurea in silica sand without carbon. These results suggest that allelopathy accounts for a substantial proportion of the total interference of Centaurea on Festuca, shifting the balance of competition in favor of Centaurea. However, Centaurea outperformed Festuca even in the presence of activated carbon, demonstrating the importance of the combined roles of resource competition and allelopathy.

Allelopathic evidence in Brachiaria decumbens and its potential to invade the Brazilian Cerrados

“…However, the great success of B. decumbens on invading cerrados could in part be due to allelopathy, as suggested in other parts of the world by authors who related allelopathy to biological invasions (Hiero and Callaway, 2003;Vivanco et al,. 2004;Ridenour and Callaway, 2001;Vaughn and Berhow, 1999).…”

“…Some of these attributes are: vegetative and sexual reproduction, high productivity and high growth rates due to efficient photosynthetic processes and the effective use of nutrients, large production of easily dispersed seeds with high germination rates, short life cycles, and allelopathy (D'Antonio and Vitousek, 1992;Cronk and Fuller, 1995;Rejmánek and Richardson, 1996;Williamson, 1996;Kolar and Lodge, 2001). Allelopathy, simply defined as "the release of phytotoxins by plants" (Bais et al, 2003) can enhance the competitive success of the plant invaders, since the release of these phytotoxins in the environment may affect the growth and life processes of other community species (Whittaker and Feeney, 1971;Rice, 1984;Ridenour and Callaway, 2001;Callaway, 2002). The Brazilian cerrado is recognized as the richest savanna in the world concerning plant species, and it integrates the list of global hot spots (Myers et al, 2000;Mittermeier et al, 2004).…”

Allelopathic and autotoxicity effects of barley (Hordeum vulgare L. ssp. vulgare) root exudates

“…The relative importance of allelopathy and competition in plant-plant interactions has been debated but seldom tested (Fuerst and Putnam 1983;Nilsson 1994;Weidenhamer 1996;Ridenour and Callaway 2001), primarily because it is difficult to separate the effects of each phenomenon (Qasem and Hill 1989), hampering research on allelopathy in natural and cultivated plants.…”

Allelopathy as a mechanism for the invasion of Typha angustifolia

“…We believe soluble phenolics are the most likely class of allelochemicals in T. angustifolia for three reasons. First, soluble phenolics have been identified as a major class of allelochemicals (Rice 1984, Blum 1996Inderjit 1996) and are the most common allelochemicals in temperate ecosystems (Blum 1998). Second, soluble phenolics may be important allelochemicals in aquatic and wetland ecosystems because they are amphiphilic, meaning that they have both hydrophilic and hydrophobic regions.…”