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

Abstract

Elevated tropospheric ozone concentration (O3) increases oxidative stress in vegetation and threatens the stability of crop production. Current O3 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 O3 stress. Using Free Air Concentration Enrichment (FACE) technology, we investigated the impacts of elevated O3 (~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 O3 concentration reduced net CO2 assimilation rate (A), stomatal conductance (gs), and 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. These results suggest that switchgrass exhibits a greater O3 tolerance than maize, and provide important fundamental data for evaluating the yield stability of a bioenergy feedstock crop and for exploring O3 sensitivity among bioenergy feedstocks.

Ozone tolerant maize hybrids maintain Rubisco content and activity during long‐term exposure in the field

“…In C 4 crops, Rubisco is located in the bundle sheath cells, and, therefore, may be more isolated from O 3 -induced ROS. However, previous work indicated that bundle sheath proteins are more susceptible to oxidative damage than mesophyll cell proteins (Kingston-Smith & Foyer, 2000), and Rubisco activity and transcript levels were significantly reduced in sugarcane (Grantz et al, 2012), switchgrass (Li et al, 2019) and juvenile maize (Leitao et al, 2007, b) exposed to elevated O 3 . Our previous research revealed significant genetic variation in the photosynthetic response of maize hybrids and indicated that the mechanisms of response to O 3 may also vary among diverse hybrids (Choquette et al, 2019).…”

“…However, fewer studies investigated the physiological impacts of O 3 stress on C 4 plants, including maize, the most widely produced grain crop in the world (FAO, 2018), in part because early studies showed that C 4 crops were more O 3 tolerant than C 3 crops (Heagle et al, 1988;Miller, 1988). Despite this, more recent modeling studies have predicted significant impacts of O 3 on C 4 crops (Avnery et al, 2011;McGrath et al, 2015;Mills et al, 2018b;Mills, Sharps, et al, 2018c;Van Dingenen et al, 2009), and experimental studies have shown that C 4 plants are also sensitive to O 3 pollution (Grantz & Vu, 2009;Grantz, Vu, Tew, & Veremis, 2012;Leisner & Ainsworth, 2012;Leitao, Bethenod, & Biolley, 2007;Leitao, Maoret, & Biolley, 2007;Li, Courbet, Ourry, & Ainsworth, 2019;.…”

Bioenergy sorghum maintains photosynthetic capacity in elevated ozone concentrations

“…More recently, the BWB model has been applied to estimate the effect of elevated O 3 on the relationship between photosynthesis and g s . For example, elevated O 3 changed the relationship between photosynthesis and g s by increasing the intercept of the BWB model in rice (Masutomi et al, 2019), but did not alter BWB model parameters in switchgrass (Li, Courbet, Ourry, & Ainsworth, 2019). However, it is unclear how elevated O 3 concentration alters the parameters of these stomatal models in different sorghum lines.…”

“…Thus, C 3 and C 4 species might respond to O 3 differently. A few studies of O 3 response in maize ( Zea mays ) (Choquette et al, 2019, 2020; Leitao, Bethenod, & Biolley, 2007; Leitao, Maoret, & Biolley, 2007; Singh, Agrawal, Shahi, & Agrawal, 2014; Yendrek, Erice, et al, 2017; Yendrek, Tomaz, et al, 2017), switchgrass ( Panicum virgatum ) (Li et al, 2019) and sugarcane ( Saccharum spp.) (Grantz & Vu, 2009; Grantz, Vu, Tew, & Veremis, 2012; Moura, Hoshika, Ribeiro, & Paoletti, 2018) have shown that elevated O 3 negatively impacts photosynthetic performance and biomass in C 4 species.…”

Age‐dependent increase in α‐tocopherol and phytosterols in maize leaves exposed to elevated ozone pollution

“…The intracellular response to the influx of ROS depends upon the duration and intensity of O 3 exposure, with calcium, hormone signaling, and MAP kinase cascades all playing a role in regulation of transcriptional and biochemical changes (Vainonen & Kangasjärvi, 2015). Under chronic O 3 stress, transcriptional changes have been associated with decreased photosynthesis (Leitao et al., 2007; Li et al., 2019; Pell et al., 1997), increased rates of mitochondrial respiration and antioxidant production (Gillespie et al., 2012; Yendrek et al., 2015), increased hormone biosynthesis (jasmonates, ethylene, and salicylic acid) (Kangasjarvi et al., 2005; Vainonen & Kangasjärvi, 2015), and early activation of several senescence‐associated genes (SAGs) (Miller et al., 1999; Fiscus et al., 2005; Kangasjarvi et al., 2005; Betzelberger et al., 2012; Gillespie et al., 2012; Yendrek et al, 2013). For example, LIGHT HARVESTING COMPLEX B6 (LHCB), encoding a minor subunit of the antennae complex responsible for transfer of light energy to photosystem II reaction centers, is an early marker of senescence (Breeze et al., 2011) and its expression is down‐regulated early in plants exposed to elevated [O 3 ] (Yendrek et al., 2013).…”