Bioenergy sorghum maintains photosynthetic capacity in elevated ozone concentrations

Abstract

Elevated tropospheric ozone concentration (O3) significantly reduces photosynthesis and productivity in several C4 crops including maize, switchgrass and sugarcane. However, it is unknown how O3 affects plant growth, development and productivity in sorghum (Sorghum bicolor L.), an emerging C4 bioenergy crop. Here, we investigated the effects of elevated O3 on photosynthesis, biomass and nutrient composition of a number of sorghum genotypes over two seasons in the field using free‐air concentration enrichment (FACE), and in growth chambers. We also tested if elevated O3 altered the relationship between stomatal conductance and environmental conditions using two common stomatal conductance models. Sorghum genotypes showed significant variability in plant functional traits, including photosynthetic capacity, leaf N content and specific leaf area, but responded similarly to O3. At the FACE experiment, elevated O3 did not alter net CO2 assimilation (A), stomatal conductance (gs), stomatal sensitivity to the environment, chlorophyll fluorescence and plant biomass, but led to reductions in the maximum carboxylation capacity of phosphoenolpyruvate and increased stomatal limitation to A in both years. These findings suggest that bioenergy sorghum is tolerant to O3 and could be used to enhance biomass productivity in O3 polluted regions.

Plasticity in stomatal behavior across a gradient of water supply is consistent among field-grown maize inbred lines with varying stomatal patterning

“…This sits between parameter estimates previously published for maize grown in controlled environment conditions (m = 3.06, Ball 1988;m = 3.23, Collatz et al, 1992;m = 4.53, Miner and Bauerle 2017;g1 = 1.281;Yun et al, 2020) and very close to a parameter estimate for maize in the field in Colorado (m = 3.72, Miner and Bauerle 2017). The results are also comparable to measurements of Panicum virgatum (m = 3.9), Miscanthus x giganteus (m = 3.3) and Sorghum bicolor (m = 4.32) grown at nearby field sites (LeBauer et al, 2013;Li et al, 2021) as well as C4 grasses in general (m = 4.1, Miner et al, 2017;m = 4.0, Franks et al, 2017). But, relatively subtle variation in gsmodel parameters can significantly impact predictions of leaf, canopy, ecosystem and global water fluxes (Franks et al, 2017;Wolz et al, 2017), so additional data collection is still needed.…”

Approaches to investigate crop responses to ozone pollution: from O3‐FACE to satellite‐enabled modeling

“…Research from SoyFACE showed elevated O 3 concentrations (approximately 100 ppb) significantly reduced leaf photosynthetic capacity in maize (Choquette et al, 2019(Choquette et al, , 2020Sorgini et al, 2019;Wedow et al, 2021b;Yendrek et al, 2017a,b), but had little or no effect on photosynthesis and biomass yield in switchgrass (Li et al, 2019a) and sorghum (Li et al, 2021). These studies also reported considerable genotypic variation in O 3 sensitivity among maize and sorghum lines (Choquette et al, 2019;Li et al, 2021;Yendrek et al, 2017a,b). In a study at the FO 3 X facility, Moura et al (2018) exposed two potted sugarcane genotypes to three levels of O 3 concentrations and found a significant reduction in plant biomass at increased [O 3 ].…”

“…More recent experiments at SoyFACE have tested the response of maize (Choquette et al, 2019(Choquette et al, , 2020Yendrek et al, 2017aYendrek et al, , 2017b and other C 4 plants, specifically sorghum and switchgrass (Li et al, 2019a(Li et al, , 2021, to a step increase in elevated [O 3 ] (100 ppb). Yendrek et al (2017a,b) grew over 200 inbred and hybrid maize lines from 2013-2015 and directly measured and modeled multiple leaf traits including instantaneous gas exchange (A and g s ), the rate limiting steps of C 4 photosynthesis (V pmax and V max ), chlorophyll content, specific leaf area, and leaf nitrogen content.…”

Elucidation of Triacylglycerol Overproduction in the C4 Bioenergy Crop Sorghum bicolor by Constraint-Based Analysis

“…The light response curve shows a linear increase in photosynthetic response up to a light intensity of about 500 μmol photon/m 2 /s with a slope of 0.064 mol CO 2 /mol photon and the dark respiration intersect of the linear was determined to be at −2.6 μmol CO 2 /m 2 /s. In another study evaluating five sorghum genotypes under field-grown conditions, respiration rates of dark-adapted leaves were on average 1.4 μmol CO 2 /m 2 /s ( Li et al, 2021 ). We therefore consider the dark respiration intersect of 2.6 μmol CO 2 /m 2 /s to represent a rather conservative estimate.…”