Photosynthetic and water relations responses to elevated CO{sub 2} in the C{sub 4} grass Andropogon gerardii
- Kansas State Univ., Manhattan, KS (United States)
Undisturbed tallgrass prairie, dominated by the C{sub 4} grass Andropogon gerardii, was exposed to ambient and elevated (double ambient) levels of atmospheric CO{sub 2} in large open-top chambers throughout the 1991 and 1992 growing seasons. Responses in leaf xylem pressure potential ({psi}), net photosynthesis (A), and stomatal conductance (g) were measured for A. gerardii grown within chambers and from adjacent field plots. In 1992, maximum photosynthetic capacity (A{sub max}), apparent quantum requirement (Q{sub r}), the photosynthetic light compensation point (LCP), and dark respiration (R{sub d}) were also measured. Midday {psi} was significantly higher in plants grown at elevated CO{sub 2} in both years; seasonally averaged {psi} was 0.48-0.70 MPa lower in 1991 (a dry year) than 1992 (a wet year). In 1991, A and g were significantly higher in plants grown at elevated vs. ambient CO{sub 2}. Increased A at elevated CO{sub 2} occurred (as much as 7.1 {mu}mol m{sup {minus}2} s{sup {minus}1}) over a broad range of temperatures (17-35 C), but the temperature optimum for A was similar at both 350 and 700 {mu}L L{sup {minus}1} CO{sub 2}. In 1992, no differences in A, A{sub max}, Q{sub r}, LCP, or R{sub d} were detected when ambient and elevated CO{sub 2} plants were compared. In plants collected from field plots, R{sub d}, LCP, and leaf N were significantly higher than in plants within the chambers indicating that a chamber effect exists for these parameters. In both years, g was significantly reduced (21%-51%) when measured at 700 vs. 350 {mu}L L{sup {minus}1} CO{sub 2}. Peak aboveground biomass was increased at elevated CO{sub 2} in 1991 but not in 1992. These data indicate that for C{sub 4} grasses, effects of elevated CO{sub 2} may only be detectable in years with significant water stress, a common occurrence in the central North American tallgrass prairies. 27 refs., 5 figs., 1 tab.
- OSTI ID:
- 35720
- Journal Information:
- International Journal of Plant Sciences, Vol. 154, Issue 4; Other Information: PBD: Dec 1993
- Country of Publication:
- United States
- Language:
- English
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