Nitrogen assimilation and growth of wheat under elevated carbon dioxide
2002
Bloom, A.J. | Smart, D.R. | Nguyen, D.T. | Searles, P.S.
Simultaneous measurements of CO2 and O2 fluxes from wheat (Triticum aestivum) shoots indicated that short-term exposures to elevated CO2 concentrations diverted photosynthetic reductant from NO3(-) or NO2(-) reduction to CO2 fixation. With longer exposures to elevated CO2, wheat leaves showed a diminished capacity for NO3(-) photoassimilation at any CO2 concentration. Moreover, high bicarbonate levels impeded NO2(-) translocation into chloroplasts isolated from wheat or pea leaves. These results support the hypothesis that elevated CO2 inhibits NO3(-) photoassimilation. Accordingly, when wheat plants received NO3(-) rather than NH4(+) as a nitrogen source, CO2 enhancement of shoot growth halved and CO2 inhibition of shoot protein doubled. This result will likely have major implications for the ability of wheat to use NO3(-)as a nitrogen source under elevated CO2.
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