Abstract
Inorganic N is available to plants from the soil as ammonium and nitrate . We studied how wheat grown hydroponically to senescence in controlled environmental chambers is affected by N form ( vs. ) and CO2 concentration (“subambient,” “ambient,” and “elevated”) in terms of biomass, yield, and nutrient accumulation and partitioning. Wheat supplied with as a sole N source had the strongest response to CO2 concentration. Plants exposed to subambient and ambient CO2 concentrations typically had the greatest biomass and nutrient accumulation under both N forms. In general -supplied plants had higher concentrations of total N, P, K, S, Ca, Zn, Fe, and Cu, while -supplied plants had higher concentrations of Mg, B, Mn, and -supplied plants contained amounts of phytate similar to -supplied plants but had higher bioavailable Zn, which could have consequences for human health. -supplied plants allocated more nutrients and biomass to aboveground tissues whereas -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 CO2 concentration.
Highlights
Nitrogen (N) is the mineral element that most often limits plant growth and primary productivity in natural and agricultural systems
Chaff, grain yield, number of heads, and kernel number (KN) were greatest at ambient CO2 levels
No other study to our knowledge has examined the influence of N form (NH4+ vs. NO−3 ) on plant nutrient relations at three different atmospheric CO2 concentrations
Summary
Nitrogen (N) is the mineral element that most often limits plant growth and primary productivity in natural and agricultural systems. Ammonium and nitrate affect crops differently when either is supplied as the sole N source (Bloom, 1997). Ammonium requires less energy to assimilate into organic compounds (Bloom, 1997), but can prove toxic if it accumulates to high concentrations within plant tissues (Cox and Reisenauer, 1973; Goyal and Huffaker, 1984). Nitrate is generally the predominant form available in aerated, temperate agricultural soils (Haynes, 1986; Bloom, 1997), and may accumulate within plant tissues to high concentrations without toxicity (Goyal and Huffaker, 1984). The presence of NH4+ , as either a sole N source or in mixed
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