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Increased C availability at elevated carbon dioxide concentration improves N assimilation in a legume
Author(s) -
ROGERS ALISTAIR,
GIBON YVES,
STITT MARK,
MORGAN PATRICK B.,
BERNACCHI CARL J.,
ORT DONALD R.,
LONG STEPHEN P.
Publication year - 2006
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2006.01549.x
Subject(s) - carbon dioxide , photosynthesis , legume , growing season , germination , amino acid , chemistry , dry weight , carbohydrate , horticulture , zoology , biology , agronomy , botany , biochemistry , organic chemistry
Plant growth is typically stimulated at elevated carbon dioxide concentration ([CO 2 ]), but a sustained and maximal stimulation of growth requires acquisition of additional N in proportion to the additional C fixed at elevated [CO 2 ]. We hypothesized that legumes would be able to avoid N limitation at elevated [CO 2 ]. Soybean was grown without N fertilizer from germination to final senescence at elevated [CO 2 ] over two growing seasons under fully open‐air conditions, providing a model legume system. Measurements of photosynthesis and foliar carbohydrate content showed that plants growing at elevated [CO 2 ] had a c . 25% increase in the daily integral of photosynthesis and c . 58% increase in foliar carbohydrate content, suggesting that plants at elevated [CO 2 ] had a surplus of photosynthate. Soybeans had a low leaf N content at the beginning of the season, which was a further c . 17% lower at elevated [CO 2 ]. In the middle of the season, ureide, total amino acid and N content increased markedly, and the effect of elevated [CO 2 ] on leaf N content disappeared. Analysis of individual amino acid levels supported the conclusion that plants at elevated [CO 2 ] overcame an early‐season N limitation. These soybean plants showed a c . 16% increase in dry mass at final harvest and showed no significant effect of elevated [CO 2 ] on leaf N, protein or total amino acid content in the latter part of the season. One possible explanation for these findings is that N fixation had increased, and that these plants had acclimated to the increased N demand at elevated [CO 2 ].