Soybean response to elevated ozone and reduced precipitation is dominated by aboveground responses to ozone and belowground responses to soil drying

The co-occurrence of elevated ozone and drought in agricultural regions is anticipated to increase and strengthen with climate change. Both stressors negatively impact leaf photosynthetic capacity and stomatal conductance, contributing to yield reductions. The interaction of ozone and drought stress is complex and under-researched, particularly in field settings. I used free air concentration enrichment of ozone and rainfall exclusion canopies to test potential interaction effects of elevated ozone and drought stress on leaf-level physiology, aboveground biomass, and belowground root growth in field-grown soybean. While drought induced stomatal closure may limit ozone damage, ozone could also disrupt this protective response by impairing stomatal response to abiotic signals. Soybean responses to combined ozone and soil moisture stress was tested over three years. Elevated ozone consistently reduced photosynthetic capacity, regardless of precipitation levels. Ozone damaged the maximum rate of carboxylation but did not impair abscisic acid production or stomatal response to drought. These findings underscore ozone’s persistent damage under drought, a scenario likely to intensify with climate change. Both elevated ozone and drought negatively impacted leaf area index in soybean, leading to reductions in total canopy size. Smaller canopies tend to produce less yield due to decreased photosynthate available for seed production. Decreases in yield were driven largely by reductions in weight per individual seed rather than due to decreased flowering or pod set. The results indicate the potential for decreased yields under future climate scenarios and underpin the need to understand the interaction between different abiotic stresses. Minirhizotron tubes were used to take repeated images of root growth across growing seasons. Soybean responded to soil drying by increasing root length regardless of ozone concentration. The median root depth of soybean exposed to root drying increased, confirming the strong response of root growth towards soil containing more water. These results show that regardless of drought stress, elevated ozone pollution significantly impacts the aboveground productivity of soybean, while soybean roots primarily respond to reduced soil moisture in both clean and polluted atmospheres.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Plant Biology

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Martin, Duncan Gregory

Contributors dc:contributor

• Ainsworth, Elizabeth A
• Bernacchi, Carl J
• Davis, Adam S
• Yang, Wendy H

• ozone
• drought
• soybean
• photosynthesis
• yield
• roots
• global change

Statement dc:rights

• Copyright 2025 Duncan Martin

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129559

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129559