title: Soybean grown under elevated CO2benefits more under low temperature than high temperature stress: Varying response of photosynthetic limitations, leaf metabolites, growth, and seed yield.
abstract: To evaluate the combined effect of temperature and CO2on photosynthetic processes, leaf metabolites and growth, soybean was grown under a controlled environment at low (22/18°C, LT), optimum (28/24°C, OT) and high (36/32°C HT) temperatures under ambient (400μmolmol-1; aCO2) or elevated (800μmolmol-1; eCO2) CO2concentrations during the reproductive stage. In general, the rate of photosynthesis (A), stomatal (gs) and mesophyll (gm) conductance, quantum yield of photosystem II, rates of maximum carboxylation (VCmax), and electron transport (J) increased with temperature across CO2levels. However, compared with OT, the percentage increases in these parameters at HT were lower than the observed decline at LT. The photosynthetic limitation at LT and OT was primarily caused by photo-biochemical processes (49-58%, Lb) followed by stomatal (27-32%, Ls) and mesophyll (15-19%, Lm) limitations. However, at HT, it was primarily caused by Ls(41%) followed by Lb(33%) and Lm(26%). The dominance of Lbat LT and OT was associated with the accumulation of non-structural carbohydrates (e.g., starch) and several organic acids, whereas this accumulation did not occur at HT, indicating increased metabolic activities. Compared with OT, biomass and seed yield declined more at HT than at LT. The eCO2treatment compensated for the temperature-stress effects on biomass but only partially compensated for the effects on seed yield, especially at HT. Photosynthetic downregulation at eCO2was possibly due to the accumulation of non-structural carbohydrates and the decrease in gsand Astd(standard A measured at 400μmolmol-1sub-stomatal CO2concentration), as well as the lack of CO2effect on gm, VCmax, and J, and photosynthetic limitation. Thus, the photosynthetic limitation was temperature-dependent and was primarily influenced by the alteration in photo-biochemical processes and metabolic activities. Despite the inconsistent response of photosynthesis (or biomass accumulation) and seed yield, eCO2tended to fully or partially compensate for the adverse effect of the respective LT and HT stresses under well-watered and sufficient nutrient conditions.
authors: Crop Systems and Global Change Laboratory, USDA-ARS, Beltsville, MD 20705, USA; College of Agronomy, Sichuan Agricultural University, Chengdu, China.
authors: Guangli
authors: G
authors: Xu
authors: Crop Systems and Global Change Laboratory, USDA-ARS, Beltsville, MD 20705, USA; Wye Research and Education Center, University of Maryland, MD, USA. Electronic address: shardendu.singh@ars.usda.gov.
authors: Shardendu K
authors: SK
authors: Singh
authors: Crop Systems and Global Change Laboratory, USDA-ARS, Beltsville, MD 20705, USA.
authors: Vangimalla R
authors: VR
authors: Reddy
authors: Crop Systems and Global Change Laboratory, USDA-ARS, Beltsville, MD 20705, USA.
authors: Jinyoung Y
authors: JY
authors: Barnaby
authors: Crop Systems and Global Change Laboratory, USDA-ARS, Beltsville, MD 20705, USA.
authors: Richard C
authors: RC
authors: Sicher
authors: College of Agronomy, Sichuan Agricultural University, Chengdu, China.
authors: Tian
authors: T
authors: Li
mesh_terms: D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism*; D002264:Carboxylic Acids / Q000378:metabolism; D003080:Cold Temperature; D004579:Electron Transport; D006358:Hot Temperature; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000254:growth & development / Q000502:physiology; D013025:Glycine max / Q000254:growth & development / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D002264:Carboxylic Acids; D045332:Photosystem II Protein Complex; D002245:Carbon Dioxide
keywords: Carbohydrate; Organic acids; Over compensation; Photosynthetic limitation; Quantum yield; Starch