The stimulatory effect of e[CO2] on plant growth is dependent on adequate nutrient supply. For example,
N concentrations in plant tissues generally decrease under e[CO2], which in leaves is commonly
related to a decrease in Rubisco concentration and activity, and therefore linked to photosynthetic downward
acclimation. This effect is also of direct concern for food production where decreased N and protein
content can have negative effects on product quality (e.g. grain protein). Plant nutrient metabolism
appears to adjust to a new physiological equilibrium under e[CO2] which limits the extent to which
nutrient application can ameliorate the situation. What the control points are for an adjustment of plant
N metabolism is unclear. Rubisco metabolism in leaves, N assimilation, N translocation or N uptake are
all potential key steps that may be inhibited or downregulated under e[CO2]. To achieve the best possible
growth response whilst maintaining product quality, it is important to understand plant nutrient
metabolism under e[CO2].