Leaf photosynthesis and carbohydrate dynamics of soybeans grown throughout their life‐cycle under Free‐Air Carbon dioxide Enrichment

• Published in: Plant, cell and environment cell and environment, 2004-04, Vol.27 (4), p.449-458
• Main Authors: ROGERS, A., ALLEN, D. J., DAVEY, P. A., MORGAN, P. B., AINSWORTH, E. A., BERNACCHI, C. J., CORNIC, G., DERMODY, O., DOHLEMAN, F. G., HEATON, E. A., MAHONEY, J., ZHU, X.‐G., DELUCIA, E. H., ORT, D. R., LONG, S. P.
• Format: Article
• Language: English
• Subjects: atmospheric change; Biological and medical sciences; chlorophyll fluorescence; electron transport; elevated carbon dioxide concentration; FACE; Fundamental and applied biological sciences. Psychology; global climate change; Glycine max; Metabolism; photosynthesis; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; stomatal conductance
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2004.01163.x

A lower than theoretically expected increase in leaf photosynthesis with long‐term elevation of carbon dioxide concentration ([CO2]) is often attributed to limitations in the capacity of the plant to utilize the additional photosynthate, possibly resulting from restrictions in rooting volume, nitrogen supply or genetic constraints. Field‐grown, nitrogen‐fixing soybean with indeterminate flowering might therefore be expected to escape these limitations. Soybean was grown from emergence to grain maturity in ambient air (372 µmol mol−1[CO2]) and in air enriched with CO2 (552 µmol mol−1[CO2]) using Free‐Air CO2 Enrichment (FACE) technology. The diurnal courses of leaf CO2 uptake (A) and stomatal conductance (gs) for upper canopy leaves were followed throughout development from the appearance of the first true leaf to the completion of seed filling. Across the growing season the daily integrals of leaf photosynthetic CO2 uptake (A′) increased by 24.6% in elevated [CO2] and the average mid‐day gs decreased by 21.9%. The increase in A′ was about half the 44.5% theoretical maximum increase calculated from Rubisco kinetics. There was no evidence that the stimulation of A was affected by time of day, as expected if elevated [CO2] led to a large accumulation of leaf carbohydrates towards the end of the photoperiod. In general, the proportion of assimilated carbon that accumulated in the leaf as non‐structural carbohydrate over the photoperiod was small (