Effects of elevated atmospheric CO₂ concentration on nonstructural carbohydrates and grain quality of maize

We used open-top chambers (OTCs) to simulate the conditions of elevated atmospheric CO₂ concentration at the Changwu State Key Agro-Ecological Experimental Station of the Loess Plateau. There were three treatments, CK (maize grown under field conditions with natural atmospheric CO₂ concentration), OTC (maize grown in the open-top chamber under natural atmospheric CO₂ concentration), and OTC_e (maize grown in the open-top chamber under elevated atmospheric CO₂ concentration of 700 μmol·mol^-1).We explored the responses of non-structural carbohydrate (NSC) and grain quality (soluble sugar, starch and crude protein) of spring maize to elevated CO₂ at different growth stages, aiming to provide scientific basis for revealing the adaptation mechanism of maize to elevated CO₂. The results showed that the effects of elevated CO₂ on NSC content and accumulation in maize varied across organs and growth periods. Elevated CO₂ promoted the activation and redistribution of NSC in leaves, stems and roots during reproductive growth period, and significantly increased the amount of NSC conversion to the grains (ATM_NSC), as well as the conversion rate to the grains (AR_NSC) and the contribution to the grains (AC_NSC) in leaves, stems and roots. Compared with CK, the warming effect of OTC inhibited the activation and redistribution of NSC in stems and roots, but promoted the activation and redistribution of NSC in leaves, significantly increased the ATM_NSC, AR_NSC, and AC_NSC of maize leaves. Elevated CO₂ did not affect the contents of soluble sugar, starch, and crude protein in maize grains.