Elevated Ozone Concentration Reduces Photosynthetic Carbon Gain but Does Not Alter Leaf Structural Traits, Nutrient Composition or Biomass in Switchgrass
Shuai Li | Galatéa Courbet | Alain Ourry | Elizabeth A. Ainsworth
Elevated tropospheric ozone concentration (O<sub>3</sub>) increases oxidative stress in vegetation and threatens the stability of crop production. Current O<sub>3</sub> pollution in the United States is estimated to decrease the yields of maize (<i>Zea mays</i>) up to 10%, however, many bioenergy feedstocks including switchgrass (<i>Panicum virgatum</i>) have not been studied for response to O<sub>3</sub> stress. Using Free Air Concentration Enrichment (FACE) technology, we investigated the impacts of elevated O<sub>3</sub> (~100 nmol mol<sup>−1</sup>) 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<sub>3</sub> concentration reduced net CO<sub>2</sub> assimilation rate (<i>A</i>), stomatal conductance (<i>g</i><sub>s</sub>), and maximum CO<sub>2</sub> saturated photosynthetic capacity (<i>V</i><sub>max</sub>), 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<sub>3</sub> tolerance than maize, and provide important fundamental data for evaluating the yield stability of a bioenergy feedstock crop and for exploring O<sub>3</sub> sensitivity among bioenergy feedstocks.
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