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Title: Elevated CO2 plus chronic warming reduces nitrogen uptake and levels or activities of nitrogen -uptake and -assimilatory proteins in tomato roots

Author
item JAYAWARDENA, DILEEPA - University Of Toledo
item HECKATHORN, SCOTT - University Of Toledo
item BISTA, DEEPESH - University Of Toledo
item MISHRA, SASMITA - Kean University
item Boldt, Jennifer
item Krause, Charles

Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 1/19/2017
Publication URL: http://handle.nal.usda.gov/10113/5714854
Citation: Jayawardena, D.M., Heckathorn, S.A., Bista, D.R., Mishra, S., Boldt, J.K., Krause, C.R. 2017. Elevated CO2 plus chronic warming reduces nitrogen uptake and levels or activities of nitrogen -uptake and -assimilatory proteins in tomato roots. Physiologia Plantarum. 159:354-365.

Interpretive Summary: Atmospheric CO2 enrichment often enhances plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate or ammonium, using membrane-localized transport proteins in roots. These transporters may be key targets for improving N use efficiency in plants. The objective of this study was to investigate the potential interactive effects of elevated CO2, chronic warming, and N form on N uptake and the activities and concentrations of N-uptake and N-assimilatory proteins. Tomato plants were grown at two levels of CO2 (400 or 700 ppm) and two temperature regimes (30 or 37 C), with nitrate or ammonium as the N source. Elevated CO2 plus chronic warming severely inhibited plant growth, whereas individually they each had small effects on growth. Elevated CO2 plus warming decreased (1) N uptake rate by roots, (2) total protein concentration in roots, and (3) shoot %N. In addition, elevated CO2 plus warming reduced nitrate uptake rate per g root and was correlated with a decrease in the concentration of nitrate-uptake proteins per g root, whereas reduced ammonium uptake was correlated with decreased activity of ammonium-uptake proteins. Reduced N assimilation was correlated with decreased concentration of N-assimilatory proteins. Findings from this study indicate that individually, elevated CO2 and chronic warming may not impact plant nutrient uptake and assimilation, but in combination, they may hinder nutrient uptake and assimilation, and thereby decrease the growth and food quality of crop plants. Hence, future efforts to improve crop productivity and quality should include a focus on minimizing detrimental effects of warming and elevated CO2 on nutrient-uptake and -assimilation proteins.

Technical Abstract: Atmospheric CO2 enrichment is expected to often benefit plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate (NO3-) or ammonium (NH4+), using membrane-localized transport proteins in roots, which are key targets for improving N use. Though interactive effects of elevated CO2, chronic warming, and N form on N relations are expected, these have not been studied. In this study, tomato (Solanum lycopersicum) plants were grown at two levels of CO2 (400 or 700 ppm) and two temperature regimes (30 or 37oC), with NO3- or NH4+ as the N source. Elevated CO2 plus chronic warming severely inhibited plant growth, regardless of N form, while individually they had smaller effects on growth. Although %N in roots was similar among all treatments, elevated CO2 plus warming decreased (1) N uptake rate by roots, (2) total protein concentration in roots, indicating an inhibition of N assimilation, and (3) shoot %N, indicating a potential inhibition of N translocation from roots to shoots. Under elevated CO2 plus warming, reduced NO3- uptake rate per g root was correlated with a decrease in the concentration of NO3--uptake proteins per g root, reduced NH4+ uptake was correlated with decreased activity of NH4+-uptake proteins, and reduced N assimilation was correlated with decreased concentration of N-assimilatory proteins. These results indicate that elevated CO2 and chronic warming can act synergistically to decrease plant N uptake and assimilation; hence, future global warming may decrease both plant growth and food quality (%N).