In a collaborative effort between the Feedstock Production and Sustainability themes at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI), researchers have delved into the impact of elevated ozone (O3) on various crops, shedding light on the contrasting tolerance levels between C3 and C4 crops. The findings, published in Proceedings of the National Academy of Sciences, emphasize the importance of understanding plant tolerance to O3 in the face of an increasingly polluted atmosphere.
Ozone in the troposphere, formed when pollutants such as nitrogen oxides and volatile organic compounds react in the presence of sunlight, has been linked to decreased crop yields globally. This airborne pollutant poses a threat to food production and agriculture, necessitating a deeper understanding of how different crops respond to elevated O3 concentrations.
The study focused on five C3 crops (chickpea, rice, snap bean, soybean, wheat) and four C4 crops (sorghum, maize, Miscanthus × giganteus, switchgrass). C3 and C4 crops differ in their carbon-fixation pathways during photosynthesis, with C3 plants producing a 3-carbon molecule and C4 plants starting with a 4-carbon molecule. The research aimed to provide insight into the sensitivity of these crops to O3 pollution.
The results revealed that C4 crops demonstrated significantly greater tolerance to high O3 concentrations compared to C3 crops. Lisa Ainsworth, Research Leader of the U.S. Department of Agriculture Agricultural Research Service’s Global Change and Photosynthesis Research Unit, emphasized that understanding the tolerance of C4 bioenergy crops to air pollutants is crucial for strategic deployment across landscapes globally.
The study synthesized available literature and unpublished data from open-air field experiments conducted over the past two decades, quantifying the impact of O3 on crop physiology and production. The research concluded that C3 crops are more sensitive to elevated O3 than their C4 counterparts.
The anatomical features, stomatal conductance, and metabolic rates of C3 and C4 crops contribute to the differential sensitivity. Reactive oxygen species generated from O3 degradation can damage mesophyll cells in C3 plants where photosynthesis occurs. In contrast, the spatial separation of the C4 photosynthesis pathway in C4 plants helps prevent O3 from infiltrating the bundle sheath cells where sugars are produced, leading to superior tolerance.
With ozone pollution on the rise globally, the study’s findings provide valuable insights for crop management and O3 tolerance improvement. C4 crops, particularly bioenergy feedstocks, have the potential to maintain productivity in regions with high O3 levels, offering a strategic approach to address the challenges posed by air pollution in agriculture.