Moving toward effective ozone flux assessment

Area of Science:

• Plant physiology and environmental stress response.
• Ozone (O3) phytotoxicity and risk assessment.
• Biochemical and metabolic indicators of plant stress.

Background:

• Ozone (O3) is a significant atmospheric pollutant impacting plant health and crop yields.
• Current methods for assessing plant O3 sensitivity often rely on complex physiological measurements.
• Dizengremel et al. proposed simplified indices to quantify plant O3 sensitivity.

Discussion:

• The comment evaluates the proposed indices: reducing power (linked to antioxidant regeneration via the Halliwell/Asada cycle and NADPH), Rubisco/PEPc ratio (reflecting energy balance), and water-use efficiency (approximating carbon gain to O3 uptake).
• These indices offer a potentially straightforward yet scientifically robust approach for O3 risk assessment.
• The feasibility of translating these indices into routine use and modeling is acknowledged, despite potential costs.

Key Insights:

• Reducing power, influenced by photosynthetic light reactions supplying NADPH, is a key metabolic indicator of O3 sensitivity.
• The Rubisco/PEPc ratio serves as a valuable index for understanding the plant's energy balance under stress.
• Water-use efficiency provides a time-integrated measure correlating carbon gain with stomatal O3 uptake.

Outlook:

• Extensive experimental validation of these proposed indices under diverse and realistic environmental conditions is crucial.
• Successful validation will enable the reliable transfer of findings to field applications and effective O3 flux modeling.
• Further research should focus on integrating these metabolic indicators into broader plant defense and stress response models.