title: The effect of ammonium and nitrate on carbondioxide compensation point and enzymes associated with carbondioxide exchange in wheat.
abstract: The carbondioxide compensation point (Γ), dry matter production, and the activities of nitrate reductase (NR), glycolate oxidase (GO), ribulose 1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC) were measured in wheat, grown on media, containing nitrate or ammonium. Significantly higher Γ and lower dry matter was observed in plants supplied with ammonium-nitrogen (NH4-N), as compared to those supplied with nitrate-nitrogen (NO3-N). The activities of NR and PEPC were higher in plants grown on NO3-N than to those grown on NH4-N. There were no significant differences in the activities of GO and RuBPC irrespective of whether NO3-N or NH4-N was supplied. None of the enzymes was found to be associated directly with the Γ.PEPC activity accounted the measured differences in the Γ and biomass production between NH4-N and NO3-N supplied plants. The relationship between PEPC and the Γ is discussed.
authors.affiliation: Division of Plant Physiology, Indian Agricultural Research Institute, 110 012, New Delhi, India.
authors.forename: S N
authors.initials: SN
authors.lastname: Sharma
authors.forename: G S
authors.initials: GS
authors.lastname: Sirohi