title: Effects of low and elevated CO2on C3and C4annuals : I. Growth and biomass allocation.
abstract: In order study C3and C4plant growth in atmospheric CO2levels ranging from past through predicted future levels, Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) were grown from seed in growth chambers controlled at CO2partial pressures of 15 Pa (below Pleistocene minimum), 27 Pa (pre-industrial), 35 Pa (current) and 70 Pa (predicted future). After 35 days of growth, CO2had no effect on the relative growth rate, total biomass or partitioning of biomass in the C4species. However, the C3species had greater biomass accumulation with increasing CO2partial pressure. C3plants grown in 15 Pa CO2for 35 days had only 8% of the total biomass of plants grown in 35 Pa CO2, C3plants had lower relative growth rates and lower specific leaf mass than plants grown in higher CO2partial pressures, and aborted reproduction. C3plants grown in 70 Pa CO2had greater root mass and root-to-shoot ratios than plants grown in lower CO2partial pressures. These findings, support other studies that show C3plant growth is more responsive to CO2partial pressure than C4plant growth. Differences in growth responses to CO2levels of the Pleistocene through the future suggest that competitive interactions of C3and C4annuals have changed through geologic time. This study also provided evidence that C3annuals may be operating near a minimum CO2partial pressure for growth and reproduction at 15 Pa CO2.
authors.affiliation: Department of Botany, Duke University, 27708-0340, Durham, NC, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Dippery
authors.affiliation: Department of Botany, Duke University, 27708-0340, Durham, NC, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Tissue
authors.affiliation: Department of Botany, Duke University, 27708-0340, Durham, NC, USA.
authors.forename: R B
authors.initials: RB
authors.lastname: Thomas
authors.affiliation: Department of Botany, Duke University, 27708-0340, Durham, NC, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Strain
keywords: Abutilon theophrasti; Amaranthus retroflexus; Growth; Low CO2; Reproduction