|Ainsworth, Elizabeth - Lisa|
|Leakey, Andrew d b|
Submitted to: Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/2/2009
Publication Date: 9/15/2009
Citation: Rogers, A., Ainsworth, E.A., Leakey, A.D.B. 2009. Will Elevated Carbon Dioxide Concentration Amplify the Benefits of Nitrogen Fixation in Legumes? Plant Physiology. 151:1009-1016. Interpretive Summary: Legumes have the capability to exchange carbon for nitrogen with their nitrogen-fixing symbionts. Therefore, the ability to match the increase in carbon supply with an increased supply of nitrogen is hypothesized to give legumes a competitive advantage over non-leguminous species when grown at elevated carbon dioxide concentration. On balance, evidence suggests that in managed agricultural systems, legumes are more responsive to elevated carbon dioxide than other plants; however, in natural ecosystems, nutrient availability appears to limit the response of nitrogen fixation to elevated carbon dioxide concentration. In this paper, we consider this central dogma, outline the mechanisms that underlie it, and examine recent work that advances current understanding of how legumes both capitalize on the benefits, and limit the deleterious effects of growth at elevated carbon dioxide.
Technical Abstract: Current evidence suggests there are three key features of the response of legumes to elevated [CO2]: (1) unlike other non-leguminous C3 plants, only legumes have the potential to maximize the benefit of elevated [CO2] by matching stimulated photosynthesis with increased N2 fixation; (2) this potential can only be realized in the absence of limitations on N2 fixation such as additional nutrient deficiencies, low temperature or drought; (3) rising [CO2] may offer some protection from drought-induced decreases in N2 fixation which will be become more prevalent with projected changes in precipitation intensity and frequency that are projected to accompany the rise in [CO2]. However, despite the considerable importance of legumes to both agriculture and the function of natural ecosystems, there are still a number of key knowledge gaps in the synthesis described above. There have been very few studies of legume response to elevated [CO2] in long-term field studies. This greatly limits characterization of the environmental conditions under which N2 fixation can or cannot be stimulated at elevated [CO2]. The feedback effects of nutrient limitation on N2 fixation and photosynthesis have not been quantified. Only a single leguminous food crop (soybean) has been the subject of a fully open-air CO2 enrichment experiment, and this study has not yet reported the effects on N2 fixation. No study we are aware of has quantitatively assessed the flow of C to nodules at current and elevated [CO2]. These and other challenges create the prospect of many new and exciting findings in this subject area.