Bioenergy Sorghum Maintains Photosynthetic Capacity in Elevated Ozone Concentrations

Li, S., Moller, C.A., Mitchell, N.G., Lee, D.K., Ainsworth, E.A. Jan. 21, 2021. “Bioenergy Sorghum Maintains Photosynthetic Capacity in Elevated Ozone Concentrations.” Plant, Cell & Environment 44 (3), 729-746. DOI: 10.1111/pce.13962.

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.

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