Elevated atmospheric CO2 does not affect per se the preference for symbiotic nitrogen as opposed to mineral nitrogen of Trifolium repens L

Autor: Ueli A. Hartwig, Josef Nösberger, Silvia Zanetti
Rok vydání: 1998
Předmět:
Zdroj: Plant, Cell and Environment. 21:623-630
ISSN: 1365-3040
0140-7791
DOI: 10.1046/j.1365-3040.1998.00307.x
Popis: The objective of this investigation was to examine the effect of an elevated atmospheric CO 2 partial pressure (pCO 2 ) on the N-sink strength and performance of symbiotic N 2 fixation in Trifolium repens L. cv. Milkanova. After initial growth under ambient pCO 2 in a nitrogen-free nutrient solution, T. repens in the exponential growth stage was exposed to ambient and elevated pCO 2 (35 and 60 Pa) and two levels of mineral N (N-free and 7.5 mol m -3 N) for 36 d in single pots filled with silica sand in growth chambers. Elevated pCO 2 evoked a significant increase in biomass production from day 12 after the start of CO 2 enrichment. For plants supplied with 7.5 mol m -3 N, the relative contribution of symbiotically fixed N (%N svm ) as opposed to N assimilated from mineral sources ( 15 N-isotope-dilution method), dropped to 40%. However, in the presence of this high level of mineral N, %N sym was unaffected by atmospheric pCO 2 over the entire experimental period. In plants fully dependent on N 2 fixation, the increase in N yield reflects a stimulation of symbiotic N 2 fixation that was the result of the formation of more nodules rather than of higher specific N 2 fixation. These results are discussed with regard to physiological processes governing symbiotic N 2 fixation and to the response of symbiotic N 2 fixation to elevated pCO 2 in field-grown T. repens.
Databáze: OpenAIRE
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