Effects of elevated [CO2] on photosynthesis and seed yield parameters in two soybean genotypes with contrasting water use efficiency

Authors: SOBA, DAVID - Consejo Superior De Investigaciones Cientificas (CSIC); SHU, TIANCHU - Auburn University; Runion, George; Prior, Stephen - Steve; FRITSCHI, FELIX - University Of Missouri; ARANJUELO, IKER - Consejo Superior De Investigaciones Cientificas (CSIC); SANZ-SAEZ, ALVARO - Auburn University

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2020
Publication Date: 7/13/2020
Citation: Soba, D., Shu, T., Runion, G.B., Prior, S.A., Fritschi, F., Aranjuelo, I., Sanz-Saez, A. 2020. Effects of elevated [CO2] on photosynthesis and seed yield parameters in two soybean genotypes with contrasting water use efficiency. Environmental and Experimental Botany. 178:104154. https://doi.org/10.1016/j.envexpbot.2020.104154.
DOI: https://doi.org/10.1016/j.envexpbot.2020.104154

Interpretive Summary: The rise in atmospheric CO2 will likely increase photosynthesis and seed yield in soybean [Glycine max (L.) Merr.]. But breeding for high water use efficiency (WUE) could change carbon uptake by leaves and seed nutrient levels under high CO2 due to lower stomatal conductance. This study looked at two cultivars with different WUE under ambient and elevated CO2 atmospheric conditions. Results showed that the low WUE cultivar had higher photosynthesis under high CO2 due to higher stomatal conductance, while the high WUE cultivar compensated by producing more leaf area. But improved photosynthesis did not translate into more biomass or seed yield under high CO2 compared to the high WUE cultivar that had better assimilate partitioning. The high WUE cultivar generally had lower seed mineral concentrations but higher total nutrient amounts due to increased seed yield under high CO2 vs the low WUE cultivar. Findings showed important genetic variation in soybean response to elevated atmospheric CO2 that need to be considered in breeding for future CO2 scenarios.

Technical Abstract: The predicted increase in atmospheric CO2 concentration [CO2] is expected to increase photosynthesis and seed yield in crops such as soybean [Glycine max (L.) Merr.]. However, future breeding for high water use efficiency (WUE) could interfere with the amount of carbon fixed by leaves and seed mineral composition under elevated [CO2] due to lower stomatal conductance (gs). In the present study, two cultivars with contrasting WUE under ambient (410 ppm; a[CO2]) and elevated (610 ppm; e[CO2]) atmospheric conditions were evaluated in terms of photosynthetic performance (leaf and canopy levels) and seed mineral composition. Results showed that the low WUE cultivar had a higher response to e[CO2] in terms of photosynthetic efficiency due to higher gs, which was compensated in the high WUE cultivar by an increase in leaf area (LA). However, improved photosynthetic efficiency did not translate into greater biomass or seed yield [CO2] response compared to the high WUE cultivar, suggesting better assimilate partitioning by this cultivar. In terms of seed quality, the high WUE cultivar generally had lower mineral concentrations compared to a[CO2] and greater total nutrient amounts (due to higher seed yield) under e[CO2] compared to the low WUE cultivar. Findings highlight important genetic variation in soybean response to future atmospheric [CO2] that should be considered when breeding for future scenarios.