Effect of Inorganic Nitrogen lons on Photosynthesis and Carbon Dioxide Compensation Concentration of Themeda triandra and Zea mays

Vacuum infiltration of nitrate and ammonium ions into nitrogen-starvedleaf tissue of Themeda triandra and Zea mays increased the carbondioxide compensation point well in excess of the level normallyassociated with C₄ photosynthetic pathway plants. The net photosyntheticrate was stimulated by the nitrate ions and but slightly inhibitedby the ammonium ions. These effects were immediate. The ionsincreased the Themeda triandra carbon dioxide compensation pointand had no effect on that of Zea mays when these plants weregrown on fertilized soil. The dark respiration rates of nitrogen-starvedThemeda triandra leaves were unaffected by the infiltrationof inorganic nitrogen ions. The results suggest that photosynthesisand photorespiration are directly influenced by inorganic nitrogenions. Themeda triandra, Zen mays, net photosynthetic rate, carbon dioxide compensation points, inorganic nitrogen stimulation