Effect of Carbon Dioxide Enrichment on 15 N Natural Abundance of Leaves
Plant productivity is enhanced by elevated atmospheric CO2 concentration,but N content of leaf is reduced.How atmospheric CO2 affects leaf15N composition and the related mechanisms remain unclear.δ15N and N content of wheat and sunflower leaves were determined under two CO2 concentration(410 and 820 μmol·mol-1)treatments.The results show that the N content of both species decreases with elevated CO2 concentration,but the response of δ15 N to CO2 enrichment is different between wheat and sunflower.Under high CO2 concentration treatment,δ15 N of wheat leaves decreases significantly by 6.5‰,while δ15 N of sunflower leaves increases slightly by 2.1‰,accompanied by a significant increase in leaf mass and aboveground biomass.Therefore,N nutrition characteristics of wheat are consistent with N assimilation limitation hypothesis,while the response of sunflower is consistent with dilution effect hypothesis.δ15N in wheat leaves decreases significantly with leaf aging and cell aging.Therefore,when using δ15N to infer environmental impacts on plant N metabolism,it is necessary to account for the leaf age effect.The results of meta-analysis show that δ15 N of non-legume C3 plants decreases significantly by 0.3‰ under elevated CO2 concentration,in line with our results on wheat plants.The study shows that the inhibited N assimilation is an important mechanism related to the CO2 effect on N metabolism and 15N content of plants.
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