2011 Fiscal Year Final Research Report
Tracing nitrate uptake by plants using the natural stable isotopes
| Project/Area Number |
22651001
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Single-year Grants |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Hokkaido University |
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Principal Investigator |
TSUNOGAI Urumu 北海道大学, 大学院・理学研究院, 准教授 (50313367)
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| Project Period (FY) |
2010 – 2011
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| Keywords | 硝酸 / 同化 / 三酸素同位体組成 / 植物 / アンモニア / 窒素同位体組成 / 笹 / 凍結乾燥 |
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| Research Abstract |
Nitrate(NO_3^-) is an essential nutrient for plants. In general, it is assumed that plants obtained NO_3^-only through their root tissues. However, some plants could obtain NO_3^-though leaf tissues to some extent, because significant quantities of atmospheric NO_3^-(NO_3^-_<atm>) deposit onto earth surface through wet and dry deposition. However, it was difficult to clarify and to quantify the direct NO_3^-_<atm> assimilation in past studies. The triple oxygen isotopic composition(Δ^<17>O≦δ^<17> O-0. 52×δ^<18> O) of NO_3^-can be a useful tracer to quantify the mixing ratios of NO_3^-_<atm> within total NO_3^-in plants(NO_3^-_<plant>). This is because NO_3^-_<atm> is the only source of the large^<17> O anomaly(Δ^<17O>> 0) due to the O atom contribution from^<17> O-enriched ozone. In contrast, re-mineralized NO_3^-produced biologically in a soil(NO_3^-_<soil>) shows little^<17> O anomaly(Δ^<17> O=0). Furthermore,Δ^<17> O values are stable during the post-depositional isotopic fractionat
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ion processes such as assimilation, whereas bothδ^<15> N andδ^<18> O values of NO_3^-_<plant> are variable. Therefore, the determination on theΔ^<17> O values of NO_3^-_<plant> allows us to estimate the contribution of NO_3-_<atm> in each plant tissue and to verify whether plants assimilate NO_3^-_<atm> or not. To clarify the direct NO_3^-assimilation, we determinedΔ^<17> O values of NO_3^-_<plant> in each tissue(leaf, stem and root) of Sasa, which was collected at forest floors located in campuses of Hokkaido University. We found large^<17> O anomaly in leaves(Δ^<17> O=from+2 to+13‰), whereas little^<17> O anomaly in stems and roots(Δ^<17> O=from 0 to+6‰). Therefore, we concluded the leaves contained NO_3^-_<atm> to some extent. Besides, while theΔ^<17> O values were stable in the stems and roots, the^<18> O-enrichments more than 10‰suggest the assimilation of NO_3^-_<soil> in the stems and roots. In contrast, the linear correlation betweenΔ^<17> O andδ<18>^O0values observed in leaves suggest mixing between NO_3^-<atm> and NO_3^-_<soil> within leaves. Furthermore, the^<18> O-enrichment trend during the growth seasons suggests the progress of assimilation within leaves. In conclusion, we found NO_3^-_<atm> within the plant and clarified that the plants assimilate NO_3^-_<atm> obtained through leaves to some extent. Less
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[Presentation] Tracing the fate of atmospheric nitrate deposited onto an oligotrophic lake in eastern Asia(B51H-0459)2010
Author(s)
Tsunogai, U., Daita, S., Komatsu, D. D., Nakagawa, F., Tanaka, A.
Organizer
2010 AGU Fall Meeting
Place of Presentation
Moscone Convention Center, San Francisco, California, USA
Year and Date
20101213-17
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