Closeout technical report for DOE award number DE-FG02-97ER62332 [Nitrogen budget under elevated CO{sub 2} levels: regulation by absorption and assimilation]

BassiriRad, Hormoz ; Gutschick, Vincent

University of Illinois at Chicago, Chicago, IL (United States)

关键词: Biomass;    Capacity;    Absorption;    Carbohydrates;    Kinetics;   

DOI  :  10.2172/808011
RP-ID  :  NONE
RP-ID  :  FG02-97ER62332
RP-ID  :  808011

美国|英语

来源: UNT Digital Library

【 摘 要 】

This entire project was conducted between 1995 and 1999, during which two postdocs and numerous undergraduate students received training in research. Furthermore, the funds from this grant contributed either totally or partially to the publication of 14 refereed journal articles. The focus of this research was to investigate plant nitrogen budget under elevated CO{sub 2} concentration. Of particular interest were the following: (1) Does elevated CO{sub 2} increase root carbohydrate availability? (2) Does such an enhancement increase kinetics of root nitrogen acquisition? (3) Does the effect on kinetics differ between NH{sub 4}{sup +} and NO{sub 3}{sup -}? (4) If there are interspecific differences in (1)-(3), could those variations lead to changes in community composition? This report shows that, although root carbohydrate availability often increases in response to elevated CO{sub 2}, such an increase is neither necessary nor directly related to changes in root N uptake kinetics . The data also show that, depending on species, the effects of elevated CO{sub 2} on root nitrogen uptake kinetics ranges from down regulation to no changes to up regulation. Furthermore, the effects on NH{sub 4}{sup +} are not always similar to the effects on NO{sub 3}{sup -}. Perhaps the most critical finding is the fact that in many instances a change in root N uptake kinetics alone does not provide a reliable prediction of plant N acquisition in response to elevated CO{sub 2}. It is shown that a better examination of whether plant N uptake responds to CO{sub 2} level and whether such a response can be scaled up to community level processes would require integration of knowledge of other root system characteristics. For example, it is well established that mycorrhizal fungi are important regulators of plant N uptake. The data suggest that, while elevated CO{sub 2} affects root N uptake capacity, this effect is highly dependent on the type and level of the mycorrhizal infection. Another root characteristic that significantly affects N uptake and could mask any potential impact of kinetics is root morphology. When all else is equal, increased biomass allocation to roots is the least effective mechanism in adjusting plant N uptake under elevated CO{sub 2}. Finally, plants may be able to reduce their demand for N via increased N use efficiency (NUE). The research conducted here indicates that elevated CO{sub 2} may evoke different responses in NUE depending upon species and that an increased NUE may be one of the most effective mechanisms in optimizing N uptake and growth responses to elevated CO{sub 2}. It is concluded that elevated CO{sub 2} can have a dramatic effect on root N uptake kinetics, but viewed in isolation this observation does not provide a robust assessment of plant N economy under an enriched CO{sub 2} atmosphere. Therefore, future work designed to predict whole-plant N responses to elevated CO{sub 2} must consider other root system adjustment s listed above, collectively.