title: Effects of elevated CO2 on intra-specific competition in Sinapis alba: an examination of the role of growth responses to red:far-red ratio.
abstract: Response of plants to elevated CO2 differs markedly between individually- and competitively-grown plants, both in terms of mean size and variation about the mean. Using Sinapis alba, we explored whether these contrasting effects are a consequence of the effect of competition on the red:far red (R:FR) light ratio. Plants were grown at both ambient and elevated (700 microl.l(-1)) CO2 in competitive stands, and as individuals at either a low (0.7) or high (1.25) R:FR ratio at a constant photosynthetic photon fluence rate. Elevated CO2 increased stand biomass by enhancing the growth of canopy dominants, but not the subordinates. As a consequence, elevated CO2 increased the coefficient of variation in size within the stands. Elevated CO2 did not enhance the growth of individually-grown plants at the low R:FR ratio, but did at the high R:FR ratio. Both the poor response of subordinate plants to elevated CO2 and the increased size inequalities of individuals within the stand can be explained in terms of the effect of the R:FR ratio on CO2 responsiveness. The effect of the R:FR ratio on CO2 response may be related to its effect on allocation patterns and nutrient uptake.
authors.affiliation: Department of Biology, Acadia University, Wolfville, NS, Canada.
authors.forename: J E
authors.initials: JE
authors.lastname: Cowan
authors.forename: E G
authors.initials: EG
authors.lastname: Reekie
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology*; D008027:Light; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D031226:Sinapis / Q000187:drug effects* / Q000254:growth & development / Q000528:radiation effects*
chemical_list: D002245:Carbon Dioxide