Drought and High Nighttime Temperature Impact on Soybean Seed Yield and Quality Under Ambient and Elevated CO2 Environments

Authors: THENVEETTIL, NAFLATH - Mississippi State University; BHEEMANAHALLI, RAJU - Mississippi State University; KHAREL, TULSI - US Department Of Agriculture (USDA); Reddy, Krishna; GAO, WEI - Colorado State University; REDDY, RAJA - Mississippi State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2025
Publication Date: 10/21/2025
Citation: Thenveettil, N., Bheemanahalli, R., Kharel, T.P., Reddy, K.N., Gao, W., Reddy, R.K. 2025. Drought and High Nighttime Temperature Impact on Soybean Seed Yield and Quality Under Ambient and Elevated CO2 Environments. Scientific Reports. 15, Article number: 36679 (2025). https://doi.org/10.1038/s41598-025-20392-0.
DOI: https://doi.org/10.1038/s41598-025-20392-0

Interpretive Summary: Global soybean production faces threats from abiotic stresses, such as high night-time temperatures (HNT) and drought during the reproductive stage. Rising atmospheric CO2 levels also play a role in these changes. Scientists from Mississippi State University, Colorado State University and USDA-ARS, Crop Production Systems Research Unit investigated two soybean genotypes, DS25-1 and DS31-243, grown under different conditions: control (normal soil moisture and temperature), HNT (higher night-time temperature), and drought (lower soil moisture) at both ambient (425 ppm, aCO2) and elevated (725 ppm, eCO2) CO2 levels in plant growth chambers during flowering and pod development stages. Plants with higher CO2 showed increased photosynthesis and better stress responses. Under high night-time temperatures and higher CO2, the number of pods and seeds increased. On average, the number of pods and seeds increased by 60% and 59%, respectively, under HNT and elevated CO2 compared to HNT and ambient CO2. However, drought reduced the number of pods and seeds and overall yield. High night-time temperatures and drought also affected seed protein and carbohydrate content. Seed protein content decreased under elevated CO2, while sed carbohydrate content decreased under HNT. The study showed that higher CO2 levels can positively impact plant physiology and yield, even under stress conditions.

Technical Abstract: The increasing prevalence of abiotic stresses, including high night-time temperatures (HNT) and drought during the reproductive stage, poses a risk to global soybean production. Additionally, the influence of rising atmospheric CO2 levels must be considered when addressing changes in temperature and drought conditions. In this study, two soybean genotypes, DS25-1 and DS31-243, were grown under control (0.15 m3 m-3 volumetric soil moisture content (VWC) and 30/22°C day/night temperature), HNT (30/26°C day/night temperature), and drought (0.08 m3 m-3 VWC) conditions at ambient (425 ppm, aCO2) and elevated (725 ppm, eCO2) CO2 concentrations in sunlit plant growth chambers during flowering and pod development stages. The plants exposed to eCO2 under control and drought conditions showed increased photosynthesis (DS25-1: 55 and 142%, and DS31-243: 77 and 61%) and non-photochemical quenching (DS25-1: 98 and 57%, and DS31-243: 67 and 126%) compared to aCO2. On average, the pods and seed numbers increased by 60 and 59%, respectively, under HNT and eCO2 compared to HNT and aCO2. In contrast, the drought decreased pods and seeds by 43% across genotypes and CO2 environments. This has resulted in a reduction in seed yield by 62 and 56% in DS25-1 and DS31-243, respectively, under drought compared to control. Under aCO2, the seed yield of DS31-243 was reduced by 42% under HNT compared to the control. The seed protein content was reduced under eCO2, while other treatments did not influence their content. The seed carbohydrate content decreased under the HNT condition, while the drought and eCO2 did not influence its production. The stress conditions during seed development resulted in reduced polyunsaturation while the oleic acid content increased. The study highlighted the positive impacts of eCO2 on physiology and yield.