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

Songmei Shi; Yuling Qiu; Miao Wen; Xiao Xu; Xingshui Dong; Chenyang Xu; Xinhua He

doi:10.3389/fpls.2020.609031

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

Front Plant Sci. 2021 Feb 4:11:609031. doi: 10.3389/fpls.2020.609031. eCollection 2020.

Authors

Songmei Shi¹, Yuling Qiu¹, Miao Wen¹, Xiao Xu², Xingshui Dong¹, Chenyang Xu¹, Xinhua He^{1

3}

Affiliations

¹ Centre of Excellence for Soil Biology, School of Resource and Environment, Southwest University, Chongqing, China.
² Key Laboratory of Southwest China Wildlife Resources Conservation (China West Normal University), Ministry of Education, Nanchong, China.
³ School of Biological Sciences, University of Western Australia, Perth, WA, Australia.

Abstract

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.

Keywords: CO2 enrichment; biomass production; free amino acid; mineral elements; nutrient use efficiency.