An ozone flux-response relationship for wheat

Area of Science:

• Agricultural Science
• Environmental Science
• Plant Physiology

Background:

• Ozone (O3) is a significant air pollutant impacting crop yields.
• Assessing ozone's impact on wheat (Triticum aestivum L.) requires accurate exposure indices.
• Existing indices like AOT40 may not fully capture the complex relationship between ozone exposure and crop damage.

Purpose of the Study:

• To compare the effectiveness of two ozone exposure indices, AOT40 and CFO(3), in predicting relative yield loss in wheat.
• To determine which index provides a more consistent relationship between ozone exposure and wheat yield reduction.
• To evaluate the role of environmental factors in ozone uptake and their influence on yield loss prediction.

Main Methods:

• Conducted six open-top chamber experiments with spring and winter wheat.
• Calculated AOT40 (accumulated exposure over 40 nl l⁻¹) and CFO(3) (cumulative ozone flux to flag leaves) during the grain-filling period.
• Estimated ozone uptake using a stomatal conductance model incorporating phenology, light, vapor pressure deficit (VPD), and temperature.

Main Results:

• The CFO(3) index demonstrated a more consistent relationship with relative wheat yield loss compared to AOT40, particularly for spring wheat.
• Stomatal conductance was limited by VPD in warm, dry years and by temperature in cool, humid years.
• Light primarily determined the duration of significant ozone uptake during the day.

Conclusions:

• The flux-based CFO(3) index is a more mechanistically relevant predictor of ozone-induced wheat yield loss than AOT40.
• CFO(3) is expected to estimate greater yield loss in humid regions of Europe and lesser loss in drier climates.
• A threshold for ozone flux did not enhance the performance of the CFO(3) index.