Assessment of grain quality in terms of functional group response to elevated [CO2], water and nitrogen using a meta-analysis: Grain protein, zinc and iron under future climate

The increasing [CO2] in the atmosphere increases crop productivity. However, grain quality of cereals and pulses are substantially decreased and consequently compromise human health. Meta-analysis techniques were employed to investigate the effect of elevated [CO2] (e[CO2]) on protein, zinc (Zn) and iron (Fe) concentrations of major food crops (542 experimental observations from 135 studies) including wheat, rice, soybean, field peas and corn considering different levels of water and nitrogen (N). Each crop, except soybean, had decreased protein, Zn and Fe concentrations when grown at e[CO2] concentration ( ≥550 μmol mol-1) compared ambient [CO2] (a[CO2]) concentration (≤ 380 μmol mol-1). Grain protein, Zn and Fe concentrations were reduced under e[CO2], however, the responses of protein, Zn and Fe concentrations to e[CO2 ] were modified by water stress and N. There was an increase in Fe concentration in soybean under medium N and wet conditions but non-significant. The reductions in ...