Nighttime CO2 enrichment did not increase leaf area or shoot biomass in cotton seedlings

Authors: Baker, Jeffrey; Lascano, Robert; Yates, Charles; Gitz, Dennis

Submitted to: Agriculture and Forest Meterology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2022
Publication Date: 4/20/2022
Citation: Baker, J.T., Lascano, R.J., Yates, C.E., Gitz, D.C. 2022. Nighttime CO2 enrichment did not increase leaf area or shoot biomass in cotton seedlings. Agriculture and Forest Meteorology. 320. https://doi.org/10.1016/j.agrformet.2022.108931.
DOI: https://doi.org/10.1016/j.agrformet.2022.108931

Interpretive Summary: Globally, humankind’s burning of fossil fuels, such as coal and oil is causing a rise in carbon dioxide (CO2) in the atmosphere. Rising levels of CO2 in the atmosphere is thought to be a major contributor to climate change. Over the last 60 years, ARS scientists have been studying the effects of high CO2 on plants and specifically crops used for food and fiber. The main effect of high levels of CO2 on plants is usually an increase in photosynthesis and plant growth. For many years, it was assumed that the effects of high CO2 on plants only happened during daylight hours. Because of this, many experiments lacked CO2 enrichment during the night. Recently, there have been reports of increased plant growth with high nighttime levels of CO2. We tested this idea on cotton, where we added high levels of CO2 during daytime, during the nighttime and both day and night. We found that cotton did not respond to high levels of CO2 at night. Comparing our results with previously published reports, we conclude that the effects of high CO2 at night very likely depends on the plant species under investigation.

Technical Abstract: The ongoing rise of atmospheric carbon dioxide concentration ([CO2]) has spurred the development of several experimental approaches for studying the effects of elevated [CO2] on crop plants. Some experimental designs enriched [CO2] only during the daytime hours and lacked [CO2] enrichment at night. Previous reports indicate that [CO2] enrichment at night can result in increased plant leaf area and shoot biomass. We developed small [CO2] enrichment chambers suitable for greenhouse experiments in order to test whether [CO2] enrichment at night affected plant leaf area and shoot biomass in cotton seedlings. We imposed four [CO2] treatments: 1) ambient control with no [CO2] enrichment (Amb); 2) [CO2] enrichment from 0000 to 0600 hours and 1800 to 2400 hours (Night); 3) [CO2] enrichment from 0600 to 1800 hours (Day); and 4) [CO2] enrichment continuously 24 hours day-1 (24-h). Mean and standard deviation for the [CO2] enriched periods were approximately 799.7 ± 3.4 µmol mol-1. Our results indicate that nighttime [CO2] enrichment did not result in increased cotton seedling leaf area or growth. Comparing our results with previous reports suggests that the effects of nighttime [CO2] enrichment maybe species dependent.