ELEVATED ATMOSPHERIC CO2 IMPROVES GAS EXCHANGE, WATER RELATIONS, AND GROWTH OF GRAIN SORGHUM

Authors: Wall, Gerard - Gary; BROOKS, T - UNIV OF ARIZONA; Adam, Neal; COUSINS, A - ARIZONA STATE UNIV; Kimball, Bruce; Pinter Jr, Paul; LAMORTE, R - ARS-US WATER CONS LAB; TRIGGS, J - UNIV OF ARIZONA; OTTMAN, M - UNIV OF ARIZONA; LEAVITT, S - UNIV OF ARIZONA

Submitted to: GCTE-LUCC Open Science Conference on Global Change Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/7/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Sorghum bicolor (L.) Moench was exposed to free-air CO2 enrichment (FACE) and drought to determine the effect of elevated atmospheric CO2 on stomatal conductance (gs), net assimilation rate (A), total plant water potential, biomass accumulation, and depletion of soil-water content. During 1998 and 1999 sorghum was exposed to ambient (Control: 370 umol mol-1) and FACE (ambient +200 umol mol-1) under ample (Wet, 100% replacement of evapotranspiration) and reduced (Dry, post-plant and mid-season irrigations) water supply. FACE reduced gs by 0.17 mol (H2O) m-2 s-1 (32% for Dry, 37% for Wet), which was similar to the difference between Dry and Wet. FACE increased A by 4.77 #mol (CO2) m-2 s-1 (23% for Dry and 9% for Wet), whereas Dry decreased it by 10.50 #mol (CO2) m-2 s-1 (26%). The total plant water potential was 0.16 MPa (9%) and 0.04 MPa (3%) less negative in FACE than control for Dry and Wet, respectively. Under Dry, FACE stimulated final shoot biomass by 15%. By ameliorating the adverse effects of drought, elevated atmospheric CO2 improved plant water status, which indirectly increased carbon gain.