Photosynthesis of Grass Species Differing in Carbon Dioxide Fixation Pathways: V. RESPONSE OF PANICUM MAXIMUM, PANICUM MILIOIDES, AND TALL FESCUE (FESTUCA ARUNDINACEA) TO NITROGEN NUTRITION

The response of apparent photosynthesis to N nutrition was studied in the C₃ grass, tall fescue (Festuca arundinacea Schreb.), in the C₄ species Panicum maximum Jacq., and in Panicum milioides Nees ex Trin., a species with characteristics intermediate between C₃ and C₄ photosynthetic types. Plants were grown in culture solution containing 1, 5, 50, and 200 milligrams N per liter. Apparent photosynthesis was measured on the youngest fully expanded leaves at 320 microliters of CO₂ per liter of air and 21% O₂. Leaf conductance was calculated from transpiration measurements, and CO₂ compensation concentrations were also estimated. Several leaf anatomical characteristics were studied on plastic-embedded material. Leaf N content was determined on leaves which were used in photosynthesis measurements.