In plant ecology, it is commonly observed that some plant species will facilitate the establishment or persistence of other species. Weir and Vivanco have uncovered the biochemical basis of such facilitation in North American grasslands invaded by Centaurea maculosa (spotted knapweed). The invading species produces a phytotoxin, catechin, which induces oxidative stress in many native plants and often thereby eliminates them entirely from the local ecological community. A few native species, such as Gaillardia grandiflora, are able to resist knapweed invasion, and several of these species, including Lupinus sericeus, facilitate the resistance of native grasses to the invader. Lupinus secretes oxalate from its root tissues in response to catechin exposure. By blocking reactive oxygen species, oxalate affords protection to neighboring vulnerable plants against the toxic effects of catechin. These results suggest strategies for controlling a serious invader and also provide insight into the multiplicity of facilitation mechanisms involved as plant communities develop. -- AMS
Planta 10.1007/s00425-005-0192-x (2006).
