From CO2Science: Sorghum is a C4 crop mainly grown in water-limited regions given its relatively high tolerance to drought. And although much is known about the response of this species to CO2 enrichment, less is known about how it may perform under a combination of growing conditions. Consequently, Asadi and Eshghizadeh (2021) evaluated the response of six sorghum genotypes under a full factorial design of factors that included atmospheric CO2 content (390 ppm or 700 ppm), water regime (normal irrigation vs water stressed) and nitrogen availability (normal soil conditions of 9.8 mg/kg N vs an added 105 mg/kg of N to the soil).

Paper reviewed: Asadi, M. and Eshghizadeh, H.R. 2021. Response of sorghum genotypes to water deficit stress under different CO2 and nitrogen levels. Plant Physiology and Biochemistry 158: 255-264.

The experiment was performed at Isfahan University of Technology, Isfahan, Iran, under field conditions in open-top chambers in 2018. The six sorghum genotypes examined included GS24, GS28, MGS5, Pegah, SF001 and SF002. Normal irrigation was applied after 40% depletion of available soil water. Water-stressed conditions withheld irrigation until 75% of available soil water was depleted. Following two months of treatment conditions the authors measured several plant physiological traits to ascertain the singular and combined impacts of CO2, water content and nitrogen availability.

Not surprisingly, water stress negatively impacted sorghum growth while elevated CO2 and nitrogen addition enhanced it. More specifically, averaged across all treatments drought reduced shoot dry weight by 36% whereas nitrogen addition and elevated CO2 enhanced it by 22% and 29%, respectively.

Other positive findings related to elevated CO2 included (1) an enhancement of relative water content by 10% under water deficit stress, (2) improvement of the photosynthetic apparatus, and a (3) reduction in oxidative damage and stress. Consequently, in light of all their findings, Asadi and Eshghizadeh conclude “elevated CO2 alleviated the destructive effect of water limited stress on the sorghum biochemical traits.”