PS 76-53
Nitrogen species mediates elevated CO2 effects on plant N utilization

Friday, August 9, 2013
Exhibit Hall B, Minneapolis Convention Center
Li Zhang, State Key Laboratory of Earth Surface Processes and Resource Ecology & College of Life Sciences, Beijing Normal University, Beijing, China
Dan C. Bowman, Department of Crop Science, North Carolina State University, Raleigh, NC
Kent O. Burkey, USDA, Plant Science Research Unit, NC
Xinmin Bian, Institute of Applied Ecology, Nanjing Agricultural University, Nanjing, China
Weijian Zhang, Institute of Applied Ecology, Nanjing Agricultural University, Nanjing, China
Shuijin Hu, Plant Pathology, North Carolina State University, Raleigh, NC
Background/Question/Methods

Atmospheric carbon dioxide (CO2) enrichment generally increases plant growth but reduces plant nitrogen (N) concentration. Experimental evidence suggests that elevated CO2 may inhibit plant photoassimilation of nitrate (NO3-) in C3 plants. Since NO3- is the primary source of available soil N, CO2-inhibition of plant NO3- uptake will likely reduce plant N uptake and N concentrations in cereal seeds. Manipulation of the relative availability of soil ammonium (NH4+) and NO3- may significantly affect plant N acquisition, but direct experimental evidence is still lacking. We examined the effect of different N sources on wheat growth and N utilization through manipulating inputs of N species and quantity (80 vs. 160 kg N per ha.) under two different CO2 concentrations (ambient, and ambient plus 200ppm CO2). 15N-enriched NH4+ and NO3- fertilizers were periodically applied to the soil to assess the effect of elevated CO2 on plant N uptake and growth. 

Results/Conclusions

Elevated CO2 significantly increased plants growth under both low and high N levels. However, N species significantly affected plant growth under elevated CO2. Under elevated CO2, plants were significantly larger when they received NH4+ than NO3-. Under ambient CO2, no significant differences were observed between two N sources. These results showed that different N species significantly impacted CO2 effects on plant growth, suggesting that manipulation of soil NH4+ and NO3- availability may optimize the stimulative effects of the rising CO2 on plants.