UC Davis

Inorganic N is available to plants from the soil as ammonium [Formula: see text] and nitrate [Formula: see text]. We studied how wheat grown hydroponically to senescence in controlled environmental chambers is affected by N form ([Formula: see text] vs. [Formula: see text]) and CO(2) concentration ("subambient," "ambient," and "elevated") in terms of biomass, yield, and nutrient accumulation and partitioning. Wheat supplied with [Formula: see text] as a sole N source had the strongest response to CO(2) concentration. Plants exposed to subambient and ambient CO(2) concentrations typically had the greatest biomass and nutrient accumulation under both N forms. In general [Formula: see text]-supplied plants had higher concentrations of total N, P, K, S, Ca, Zn, Fe, and Cu, while [Formula: see text]-supplied plants had higher concentrations of Mg, B, Mn, and [Formula: see text][Formula: see text]-supplied plants contained amounts of phytate similar to [Formula: see text]-supplied plants but had higher bioavailable Zn, which could have consequences for human health. [Formula: see text]-supplied plants allocated more nutrients and biomass to aboveground tissues whereas [Formula: see text]-supplied plants allocated more nutrients to the roots. The two inorganic nitrogen forms influenced plant growth and nutrient status so distinctly that they should be treated as separate nutrients. Moreover, plant growth and nutrient status varied in a non-linear manner with atmospheric CO(2) concentration.