Nitrogen assimilation and growth of wheat under elevated carbon dioxide

BLOOM AJ; SMART DR; NGUYEN DT; SEARLES PS

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2002 vol. 99 p. 1730 - 1735

0027-8424

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.