Elevated Ozone Concentration Reduces Photosynthetic Carbon Gain but Does Not Alter Leaf Structural Traits, Nutrient Composition or Biomass in Switchgrass

Elevated tropospheric ozone concentration (O(3)) increases oxidative stress in vegetation and threatens the stability of crop production. Current O(3) pollution in the United States is estimated to decrease the yields of maize (Zea mays) up to 10%, however, many bioenergy feedstocks including switchgrass (Panicum virgatum) have not been studied for response to O(3) stress. Using Free Air Concentration Enrichment (FACE) technology, we investigated the impacts of elevated O(3) (~100 nmol mol(−1)) on leaf photosynthetic traits and capacity, chlorophyll fluorescence, the Ball–Woodrow–Berry (BWB) relationship, respiration, leaf structure, biomass and nutrient composition of switchgrass. Elevated O(3) concentration reduced net CO(2) assimilation rate (A), stomatal conductance (g(s)), and maximum CO(2) saturated photosynthetic capacity (V(max)), but did not affect other functional and structural traits in switchgrass or the macro- (except potassium) and micronutrient content of leaves. These results suggest that switchgrass exhibits a greater O(3) tolerance than maize, and provide important fundamental data for evaluating the yield stability of a bioenergy feedstock crop and for exploring O(3) sensitivity among bioenergy feedstocks.