Elevated ozone concentration reduces photosynthetic carbon gain but does not alter leaf structural traits, nutrient composition, or biomass in switchgrass

Authors: LI, SHUAI - University Of Illinois; COURBET, GALATEA - Normandy University; OURRY, ALAIN - Normandy University; Ainsworth, Elizabeth - Lisa

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2019
Publication Date: 4/2/2019
Citation: Li, S., Courbet, G., Ourry, A., Ainsworth, E.A. 2019. Elevated ozone concentration reduces photosynthetic carbon gain but does not alter leaf structural traits, nutrient composition, or biomass in switchgrass. Plants. 8(4):85. https://doi.org/10.3390/plants8040085.
DOI: https://doi.org/10.3390/plants8040085

Interpretive Summary: Obtaining renewable energy from biomass feedstocks is projected to reduce reliance on traditional fossil fuels and emissions of greenhouse gases while benefitting economic growth and energy security. Switchgrass is a native perennial warm-season C4 grass and has been recognized as an emerging and promising bioenergy feedstock in the U.S. In this study, we used Free Air Concentration Enrichment (FACE) technology to fumigate switchgrass with elevated ozone concentrations, and measured photosynthetic, growth and nutrient responses to elevated ozone. Our study provides evidence that switchgrass exhibits ozone tolerance and suggest that C4 bioenergy crops including maize and switchgrass vary in ozone tolerance. Better understanding of variation in C4 bioenergy feedstock responses to air pollution could be used to strategically place feedstocks on a dynamic landscape.

Technical Abstract: Elevated tropospheric ozone concentration (O3) increases oxidative stress in vegetation and threaten the stability of crop production. Current O3 pollution in the United States is estimated to decrease the yields of maize up to 10%, however, bioenergy feedstocks including switchgrass have not been studied for response to O3 stress. Using Free Air Concentration Enrichment (FACE) technology, we investigated the impacts of elevated O3 (~100 nL L-1) on leaf photosynthetic traits and capacity, chlorophyll fluorescence, the Ball-Woodrow-Berry (BWB) relationship, respiration, structure and whole plant biomass and nutrient composition of switchgrass. Elevated O3 concentration reduced net CO2 assimilation rate (A), stomatal conductance (gs), maximum CO2 saturated photosynthetic capacity (Vmax), but did not affect other functional and structural traits in switchgrass or the macro (except potassium) and micronutrient content of leaves. In both ambient and elevated O3, leaf minor vein length per leaf area was not correlated with stomatal density, but was negatively correlated with guard cell length and stomatal pore area index. These results suggest that switchgrass exhibits a greater O3 tolerance than maize, and provide important fundamental data for modeling carbon and water cycling in bioenergy feedstocks.