The reduction in grain protein
concentration has been well documented at [eCO2] (Taub, Miller, &
Allen, 2008). However, the mechanism of reduction in grain protein
concentration at [eCO2] is still not well known. There are various
explanations and one of the common hypotheses is the
dilution of N due to the extra carbohydrate accumulation (Conroy,
1992; Gifford, Barrett, & Lutze, 2000). This explanation is highly
unlikely because biomass stimulation and reduction in grain protein
concentrations are disproportionate (Taub et al., 2008). The
most feasible explanation for lower grain protein concentration
at [eCO2] is that there is a slow and reduced remobilization of N
to the grain during reproductive development at higher [CO2]
(Seneweera et al., 2005).