Data_Sheet_1_Daytime, Not Nighttime, Elevated Atmospheric Carbon Dioxide Exposure Improves Plant Growth and Leaf Quality of Mulberry (Morus alba L.) Seedlings.docx

Almost all elevated atmospheric CO2 concentrations (eCO2) studies have not addressed the potential responses of plant growth to different CO2 in daytime and nighttime. The present study was to determine the impact of daytime and/or nighttime eCO2 on growth and quality of mulberry (Morus alba L.), a perennial multipurpose cash plant. Six-month-old mulberry seedlings were hence grown in environmentally auto-controlled growth chambers under four CO2 concentrations: (1) ambient CO2 (ACO2, 410 μmol mol–1 daytime/460 μmol mol–1 nighttime), (2) sole daytime elevated CO2 (DeCO2, 710 μmol mol–1/460 μmol mol–1), (3) sole nighttime elevated CO2 (NeCO2, 410 μmol mol–1/760 μmol mol–1), and (4) continuous daytime and nighttime elevated CO2 (D + NeCO2, 710 μmol mol–1/760 μmol mol–1). Plant growth characteristics, nutrient uptake, and leaf quality were then examined after 120 days of CO2 exposure. Compared to control, DeCO2 and (D + N)eCO2 increased plant biomass production and thus the harvest of nutrients and accumulation of leaf carbohydrates (starch, soluble sugar, and fatty acid) and N-containing compounds (free amino acid and protein), though there were some decreases in the concentration of leaf N, P, Mg, Fe, and Zn. NeCO2 had no significant effects on leaf yield but an extent positive effect on leaf nutritional quality due to their concentration increase in leaf B, Cu, starch, and soluble sugar. Meanwhile, (D + N)eCO2 decreased mulberry leaf yield and harvest of nutritious compounds for silkworm when compared with DeCO2. The reason may be associated to N, P, Mg, Fe, and Zn that are closely related to leaf pigment and N metabolism. Therefore, the rational application of mineral nutrient (especially N, P, Fe, Mg, and Zn) fertilizers is important for a sustainable mulberry production under future atmosphere CO2 concentrations.

目前绝大多数大气CO2浓度升高（elevated atmospheric CO2 concentrations, eCO2）相关研究，均未关注植物生长对日间与夜间不同CO2浓度的潜在响应。本研究旨在探究日间或夜间CO2浓度升高对多年生多用途经济作物桑树（Morus alba L.）生长与品质的影响。为此，将6月龄桑树幼苗置于环境自动控制生长箱中，设置4组CO2浓度处理：(1) 背景CO2浓度（ACO2，日间410 μmol·mol⁻¹/夜间460 μmol·mol⁻¹）；(2) 仅日间CO2浓度升高处理（DeCO2，日间710 μmol·mol⁻¹/夜间460 μmol·mol⁻¹）；(3) 仅夜间CO2浓度升高处理（NeCO2，日间410 μmol·mol⁻¹/夜间760 μmol·mol⁻¹）；(4) 昼夜持续CO2浓度升高处理（D+NeCO2，日间710 μmol·mol⁻¹/夜间760 μmol·mol⁻¹）。经过120天的CO2暴露处理后，测定植株生长特性、养分吸收量与叶片品质。与对照组相比，DeCO2与D+NeCO2处理可提升植株生物量，进而提高养分收获量与叶片碳水化合物（淀粉、可溶性糖与脂肪酸）及含氮化合物（游离氨基酸与蛋白质）的积累量，但叶片中氮、磷、镁、铁、锌的浓度有所下降。NeCO2处理对叶片产量无显著影响，但因叶片中硼、铜、淀粉与可溶性糖浓度升高，对叶片营养品质具有一定正向提升作用。与此同时，相较于DeCO2处理，D+NeCO2处理会降低桑叶产量与家蚕所需营养化合物的收获量。该现象的潜在机制可能与叶片色素及氮代谢密切相关的氮、磷、镁、铁、锌元素有关。因此，在未来大气CO2浓度背景下，合理施用矿质养分（尤其是氮、磷、铁、镁与锌）肥料，对桑树的可持续生产具有重要意义。