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Allotetraploidization between A and S (closely related to B) genome species led to the speciation of allotetraploid wheat (genome BBAA). However, the immediate metabolic outcomes and adaptive changes caused by the allotetraploidization event are poorly understood. Here, we investigated how allotetraploidization affected salinity tolerance using a synthetic allotetraploid wheat line (genome SlSlAA, labeled as 4x), its Aegilops longissima (genome SlSl, labeled as SlSl) and Triticum urartu (AA genome, labeled as AA) parents. We found that the degree of salinity tolerance of 4x was similar to its SlSl parent, and both were substantially more tolerant to salinity stress than AA. This suggests that the SlSl subgenome exerts a dominant effect for this trait in 4x. Compared with SlSl and 4x, the salinity-stressed AA plants did not accumulate a higher concentration of Na+ in leaves, but showed severe membrane peroxidation and accumulated a higher concentration of ROS (H2O2 and O2⋅⁣–) and a lesser concentration of flavonoids, indicating that ROS metabolism plays a key role in saline sensitivity. Exogenous flavonoid application to roots of AA plants significantly relieved salinity-caused injury. Our results suggest that the higher accumulation of flavonoids in SlSl may contribute to ROS scavenging and salinity tolerance, and these physiological properties were stably inherited by the nascent allotetraploid SlSlAA.

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.