Elevated CO2 increases severity of thermal hyponasty in leaves of tomato

Authors: THOMAS, MICHAEL - University Of Toledo; HECKATHORN, SCOTT - University Of Toledo; Boldt, Jennifer

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2023
Publication Date: 8/9/2023
Citation: Thomas, M.D., Heckathorn, S.A., Boldt, J.K. 2023. Elevated CO2 increases severity of thermal hyponasty in leaves of tomato. Horticulturae. 9:907. https://doi.org/10.3390/ horticulturae9080907.
DOI: https://doi.org/10.3390/ horticulturae9080907

Interpretive Summary: Climate change could have unexpected consequences for agricultural production in the future. Two environmental factors associated with climate change, temperature and carbon dioxide concentration, greatly affect the growth and development of crops. Tomatoes display unexpected growth when exposed to warm temperatures and elevated carbon dioxide concentrations which could be problematic for future tomato production. Tomato plants of all ages seem to be affected. Our study suggests that warm temperatures and elevated carbon dioxide interact with plant signaling systems that involve light sensing and the plant hormone auxin. This information can be used to help develop crops that are more resilient to the combination of warm temperatures and elevated carbon dioxide.

Technical Abstract: We previously showed that chronic warming plus elevated carbon dioxide (eCO2) causes extreme upward bending of leaflets and petioles (i.e., hyponasty) in tomato (Solanum lycopersicum), which reduces growth. In that study, only two levels of CO2 (400, 700 ppm) and temperature (30, 37 °C) were tested in young vegetative plants, and the underlying mechanism for warming + eCO2 hyponasty was not investigated. In this study, warming + eCO2 hyponasty was evaluated in tomato across a range of temperatures and CO2 concentrations, and at multiple life stages. Based on their roles in thermal hyponasty, ethylene and auxin tomato mutants were examined, and light quality manipulated, to explore the mechanism for warming + eCO2 hyponasty. At eCO2 (800 ppm), the petiole angle increased roughly linearly with temperature from 30 to 38 °C. Under high temperature stress (38 °C), the petiole angle increased similarly at all eCO2 concentrations (600/800/1000 vs. 400 ppm). All life stages examined had an increased petiole angle in leaves developed during warming + eCO2, such that most leaves in juvenile plants exhibited hyponasty but only young growing leaves did so in adults. Auxin-insensitive mutants displayed a reduced petiole angle compared to auxin-sensitive, ethylene-sensitive, ethylene-insensitive, and non-mutant genotypes, indicating that auxin, but not ethylene, is likely a main component of this hyponastic response. Reduced far-red-to-red light plus increased blue light reduced petiole hyponasty compared to non-filtered white light during warming + eCO2. These results indicate that eCO2 affects the well-characterized thermal hyponastic response of leaves, which has implications for future plant responses to climate change