Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2001
Publication Date: N/A
Technical Abstract: Photosynthesis and leaf Nitrogen (N) metabolisms are mutually dependent processes, although growth in elevated carbon dioxide (CO2) typically decreases the reduced N content of older leaves. Components of N metabolism and nitrate reductase activity (NRA) were studied in barley primary leaves in response to ambient (36 Pa) and elevated (100 Pa) growth CO2 using controlled environment chambers. Between eight and 17 days after sowing (DAS) foliar nitrate and ammonium were 27 and 42 percent lower (P < 0.01) in the elevated compared to ambient carbon dioxide treatments, respectively. Ammonium varied diurnally in the ambient but not in the elevated carbon dioxide treatment. Total and Mg2+ inhibited NRA was greatest 9 DAS but were virtually undetectable in either carbon dioxide treatment 15 DAS. Both of these enzyme activities were slightly lower (P < 0.01) in elevated compared to ambient carbon dioxide. When measured 9 DAS diurnal variations of total NRA were similar in ambient and elevated carbon dioxide, except during the latter half of the photo period when enzyme activity was decreased five to 10 percent (P < 0.05) by CO2 enrichment. The glutamate was unchanged but glutamine levels were increased by the elevated CO2 treatment between eight and 13 DAS. However, both glutamate and glutamine were negatively impacted by CO2 enrichment when leaf yellowing was observed 15 and 17 DAS. The above findings showed that other than inhibiting photo respiration, CO2 enrichment produced only slight modifications in a leaf N metabolism.