Elevated [CO2] Modified the Drought Acclimation Response in Peanut.

Peanut agroecosystems play a key role in food production and are a major source of protein in many arid and semi-arid regions where extreme weather events are expected to increase in frequency. We are taking a systems-level approach to investigate the response of peanut to elevated [CO2], water deficit and elevated temperature. Peanut cultivar C76-16 (Arachis hypogaea), a runner market type was planted in the field during two cropping seasons (2015 and 2016) in Lubbock, Texas. Seasonal continuous canopy gas exchange was measured using LiCor 7000 and six open path Canopy Evapotranspiration and Assimilation (CETA) chambers set at 400 and 650 ppm atmospheric [CO2]. A comparative analysis of leaf versus canopy gas-exchange was examined. Results showed that elevated [CO2] ameliorated the negative impact of three water deficit episodes, leading to a significant increase in above-ground biomass (47%) and pod yield (17%), but decreased harvest index compared to ambient growth conditions. Higher water use efficiency was associated with CO2 fertilization but this was linked with higher system water use. Additionally, plants grown under ambient [CO2] showed transient acclimation to water deficit stress using leaf-level gas-exchange measurements in 2015, but not 2016. Ambient-grown plants also showed acclimation to water-deficit stress at the whole-plant level in 2016. Although growth in elevated [CO2] resulted in a significant increase in both leaf-level and whole-plant assimilation, no acclimation response was seen in either year.