Responses of Arabidopsis and Wheat to Rising CO₂ Depend on Nitrogen Source and Nighttime CO₂ Levels

Abstract

A major contributor to the global carbon cycle is plant respiration. Elevated atmospheric CO 2 concentrations may either accelerate or decelerate plant respiration for reasons that have been uncertain. We recently established that elevated CO 2 during the daytime decreases plant mitochondrial respiration in the light and protein concentration because CO 2 slows the daytime conversion of nitrate (NO 3 2 ) into protein. This derives in part from the inhibitory effect of CO 2 on photorespiration and the dependence of shoot NO 3 2 assimilation on photorespiration. Elevated CO 2 also inhibits the translocation of nitrite into the chloroplast, a response that influences shoot NO 3 2 assimilation during both day and night. Here, we exposed Arabidopsis (Arabidopsis thaliana) and wheat (Triticum aestivum) plants to daytime or nighttime elevated CO 2 and supplied them with NO 3 2 or ammonium as a sole nitrogen (N) source. Six independent measures (plant biomass, shoot NO 3 2 , shoot organic N, 15 N isotope fractionation, 15 NO 3 2 assimilation, and the ratio of shoot CO 2 evolution to O 2 consumption) indicated that elevated CO 2 at night slowed NO 3 2 assimilation and thus decreased dark respiration in the plants reliant on NO 3 2. These results provide a straightforward explanation for the diverse responses of plants to elevated CO 2 at night and suggest that soil N source will have an increasing influence on the capacity of plants to mitigate human greenhouse gas emissions.

Advances in understanding CO2 responsive plant metabolomes in the era of climate change

“…In addition, elevated CO 2 during the daytime reduced mitochondrial respiration in the light and total protein amount because CO 2 decreased the daytime conversion of NO 3 -into proteins (Rubio-Asensio et al 2015). These studies clearly reflect enhanced central carbon metabolites in A. thaliana in response to elevated CO 2 .…”

Explaining the doubling of N2O emissions under elevated CO2 in the Giessen FACE via in‐field 15N tracing

“…() suggested that eCO 2 may reduce the strength of the plant N sink and thus constrain plant N utilization. Other studies have shown that eCO 2 reduced nitrate () assimilation in C3 plants (Asensio, Rachmilevitch, & Bloom, ; Bloom, Burger, Rubio‐Asensio, & Cousins, ; Bloom, Smart, Nguyen, & Searles, ) which could leave more substrate available for denitrification. In their meta‐analysis, van Groenigen et al.…”

“…Feng et al (2015) suggested that eCO 2 may reduce the strength of the plant N sink and thus constrain plant N utilization. Other studies have shown that eCO 2 reduced nitrate (NO À 3 ) assimilation in C3 plants (Asensio, Rachmilevitch, & Bloom, 2015;Bloom, Burger, Rubio-Asensio, & Cousins, 2010;Bloom, Smart, Nguyen, & Searles, 2002) which could leave more NO À 3 substrate available for denitrification. In their meta-analysis, van Groenigen et al (2011) attributed increased N 2 O emissions under eCO 2 to enhanced denitrification resulting from both higher soil labile carbon (C) and soil moisture under eCO 2 .…”

Elevated CO2 improved the growth of a double nitrate reductase defective mutant of Arabidopsis thaliana: The importance of maintaining a high energy status

“…The linkages between nitrate assimilation and photorespiration have been recently described (Fan et al, 2016) using another approach: rice plants overexpressing the nitrate transporter NRT2.3b, which enhanced yield and N content, showed both reduced photorespiration and enhanced ammonium absorption. However, providing ammonium as the main N fertilization form has been described (Britto and Kronzucker, 2002) to be deleterious for plant performance and, independent of the [CO2], biomass production is reduced under NH4 + nutrition compared to NO3nutrition under elevated CO2 (Carlisle et al, 2012;Rubio-Asensio et al, 2015;Niu et al, 2013;Rubio-Asensio and Bloom, 2016). Within this context, our study aims to discuss the mechanisms that allow NR mutant plants to substantially overcome the inhibited phenotype associated with elevated [CO2].…”

“…It was predicted that N assimilation would also be impaired under elevated [CO2] because photorespiration is diminished by enhanced [CO2] and consequently ATP synthesis is decreased (Foyer et al, 2012). Furthermore, during the night period, NO3assimilation is also reduced in plants exposed to elevated [CO2] (Rubio-Asensio et al, 2015). Such an effect would be especially important in cases where plants are exclusively fertilized with NO3 -.…”