Genotypic variation in the response of two perennial grass species to elevated carbon dioxide

Abstract

Shoot and reproductive biomass of genotypes of Bromus erectus and Dactylis glomerata grown in competition at ambient and elevated CO were examined for 2 consecutive years in order to test whether genetic variation in those traits exists and whether it is maintained over time. At the species level, a positive CO response of shoot biomass of both species was only found in the first year of treatment. At the genotype level, no significant CO×genotype interaction was found at any single harvest either for vegetative or reproductive biomass of either species. Analysis over time, however, indicated that there is a potential for evolutionary adaptation only for D. glomerata: (1) repeated measures ANOVA detected a marginally significant CO×genotype×time interaction for shoot biomass, because the range of the genotypes CO response increased over time; (2) genotypes that displayed the highest response during the first year under elevated CO also showed the highest response the second year. Null (B. erectus) or weak (D. glomerata) selective potentials of elevated CO were detected in this experiment, but short time series could underestimate this potential with perennial species.

Seedling Growth of Two Honey Mesquite Varieties Under CO2 Enrichment

“…glandulosa seedlings grown from seeds collected along an east-west precipitation gradient (36-93 cm MAP) in Texas (Derner et al 2004). These results contradict literature supporting variety-or genotype-specific responses to CO 2 enrichment for other C 3 species, including grasses (Goverde et al 2002;Roumet et al 1999Roumet et al , 2002, forbs (Andalo et al 2001), and shrubs (Atkin et al 1999). Although this leguminous shrub does not conform to responses exhibited by other C 3 plants, it is unclear whether this inconsistency results from inherent species characteristics, such as the ability to fix nitrogen, or from soil nutrient and water differences between investigations.…”

“…The relative responsiveness of these 2 honey mesquite varieties to CO 2 enrichment may indicate which will more aggressively encroach into rangelands in the future. Previous investigations have identified speciesspecific (e.g., Joel et al 2001;Goverde et al 2002) and genotype-specific (e.g., Roumet et al 2002) responses of plants to CO 2 enrichment. Dissimilar growth responses to CO 2 for these 2 honey mesquite varieties may be manifested in differential rates of shrub encroachment in arid and more mesic rangelands (Polley 1997;Polley et al 1997).…”

Effects of elevated CO2 and N on tree–grass interactions: an experimental test using Fraxinus excelsior and Dactylis glomerata

“…Recent meta-analyses indicate no systematic differences in the CO 2 responses of C3 grasses and woody species, or between fast-and slow-growing species when growing in mixed species communities (Poorter & Navas 2003). The CO 2 × N interaction obtained here for Dactylis probably stems from intraspecific competition among the grass plants in each pot, and an attenuation of the CO 2 response at low-nutrient levels (Harmens et al 2000;Roumet et al 2002). Typically at low N supply, an initial stimulation of photosynthetic rates in response to high CO 2 results in an accumulation of non-structural carbohydrates followed by a down-regulation of the plant's photosynthetic capacity (Stitt & Krapp 1999, but see Lee et al 2001).…”

“…The CO 2 × N interaction obtained here for Dactylis probably stems from intraspecific competition among the grass plants in each pot, and an attenuation of the CO 2 response at low‐nutrient levels (Harmens et al . 2000; Roumet et al . 2002).…”

Elevated Atmospheric CO2 Magnifies Intra-specific Variation in Seedling Growth of Honey Mesquite: An Assessment of Relative Growth Rates

“…Roumet et al (2002) noted that genotypes differed in response to CO 2 enrichment in only 7 of the 21 species that had been studied.…”