Global Warming Can Negate the Expected CO₂ Stimulation in Photosynthesis and Productivity for Soybean Grown in the Midwestern United States

• Published in: Plant physiology (Bethesda) Vol. 162; no. 1; pp. 410 - 423
• Main Authors: Ruiz-Vera, Ursula M., Siebers, Matthew, Gray, Sharon B., Drag, David W., Rosenthal, David M., Kimball, Bruce A., Ort, Donald R., Bernacchi, Carl J.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.05.2013
• Subjects: Agriculture; Ambient temperature; Biological and medical sciences; Biomass; Biomass production; Carbon Dioxide - pharmacology; ECOPHYSIOLOGY AND SUSTAINABILITY; Fundamental and applied biological sciences. Psychology; Global Warming; Glycine max - drug effects; Glycine max - growth & development; Glycine max - physiology; Growing seasons; Midwestern United States; Photosynthesis; Photosynthesis - drug effects; Plant Leaves - drug effects; Plant Leaves - growth & development; Plant Leaves - physiology; Plant physiology and development; Plant Transpiration - drug effects; Plants; Productivity; Rain; Soybeans; Statistical significance; Sunlight; Temperature; Temperature control; United States; North America; America; Midwestern United States; Productivity; Warming; Carbon dioxide; Stimulation; Glycine max; Dynamical climatology; Grain legume; Climate change; Leguminosae; Plant physiology; Dicotyledones; Angiospermae; Global change; Spermatophyta; Photosynthesis
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.112.211938

Extensive evidence shows that increasing carbon dioxide concentration ([CO₂]) stimulates, and increasing temperature decreases, both net photosynthetic carbon assimilation (A) and biomass production for C₃ plants. However the [CO₂]-induced stimulation in A is projected to increase further with warmer temperature. While the influence of increasing temperature and [CO₂], independent of each other, on A and biomass production have been widely investigated, the interaction between these two major global changes has not been tested on field-grown crops. Here, the interactive effect of both elevated [CO₂] (approximately 585 µmol⁻¹) and temperature (+3.5°C) on soybean (Glycine max) A, biomass, and yield were tested over two growing seasons in the Temperature by Free-Air CO₂ Enrichment experiment at the Soybean Free Air CO₂ Enrichment facility. Measurements of A, stomatal conductance, and intercellular [CO₂] were collected along with meteorological, water potential, and growth data. Elevated temperatures caused lower A, which was largely attributed to declines in stomatal conductance and intercellular [CO₂] and led in turn to lower yields. Increasing both [CO₂] and temperature stimulated A relative to elevated [CO₂] alone on only two sampling days during 2009 and on no days in 2011. In 2011, the warmer of the two years, there were no observed increases in yield in the elevated temperature plots regardless of whether [CO₂] was elevated. All treatments lowered the harvest index for soybean, although the effect of elevated [CO₂] in 2011 was not statistically significant. These results provide a better understanding of the physiological responses of soybean to future climate change conditions and suggest that the potential is limited for elevated [CO₂] to mitigate the influence of rising temperatures on photosynthesis, growth, and yields of C₃ crops.