|Leakey, Andrew d b|
Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 5/15/2008
Publication Date: 6/23/2008
Citation: Sun, J., Leakey, A., Markelz, C., Ort, D.R. 2008. Stimulated photosynthesis alters sugar and amino-acid profiles, lowers osmotic potential and improves water status of soybean leaves under free-air CO2 enrichment. American Society of Plant Biologists Annual Meeting. Paper No. P11003. Available: http://abstracts.aspb.org/pb2008/public/P11/P11003.html. Interpretive Summary:
Technical Abstract: Elevated [CO2] reduces the stomatal conductance, transpiration and soil moisture depletion of C3 and C4 species, thereby delaying the onset of drought stress. Elevated [CO2] may provide additional advantage to C3 species by enhancing drought tolerance via stimulated photosynthesis supporting greater osmo-regulation and leaf water status. This hypothesis was tested in a genomic, metabolomic and physiological investigation of soybean at the SOYbean Free-Air Concentration Enrichment (SOYFACE) field site in Illinois. Soybean was grown in four plots at ambient [CO2] (~370 ppm) and four plots at elevated [CO2] (~550 ppm), from sowing until harvest. The 2006 growing season was unusual because frequent, large rainfall events kept the soil moisture content near field capacity for the entire field season and prevented differences in transpiration from altering rates of soil moisture depletion between the ambient and elevated [CO2] plots. While this meant that drought stress was not occurring in either treatment, leaf contents of pinitol, sucrose, glucose, fructose and free amino acids were all greater at elevated [CO2]. On average across 4 development stages, the pool sizes of these metabolites generated osmotic potentials of -0.85 MPa at ambient [CO2] and -1.20 MPa at elevated [CO2]. This corresponded with average measured leaf osmotic potential of -1.47 MPa at ambient [CO2] and -1.82 MPa at elevated [CO2], as well as greater leaf turgor. The altered leaf osmotic status was associated with greater photosynthesis and greater abundance of transcripts encoding components of carbohydrate and amino acid metabolism. The overall response constitutes a direct effect of elevated [CO2] on leaf water status and a second mechanism ameliorating drought stress of C3 plants at elevated [CO2].