A meta-analysis of elevated [CO2] effects on soybean (Glycine max) physiology, growth and yield

Ainsworth, E.A. and Davey, P.A. and Bernacchi, C.J. and Dermody, O.C. and Heaton, E.A. and Moore, D.J. and Morgan, P.B. and Naidu, S.L. and Ra, H.S.Y. and ZhuX.G., X.G. and Curtis, P.S. and Long, S.P. (2002) A meta-analysis of elevated [CO2] effects on soybean (Glycine max) physiology, growth and yield. Global Change Biology, 8 (8). pp. 695-709.

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The effects of elevated [CO2] on 25 variables describing soyabean physiology, growth and yield are reviewed using meta-analytical techniques. This is the first meta-analysis to our knowledge performed on a single crop species and summarizes the effects of 111 studies. These primary studies include numerous soyabean growth forms, various stress and experimental treatments, and a range of elevated [CO2] levels (from 450 to 1250 ppm), with a mean of 689 ppm across all studies. Stimulation of soyabean leaf a CO2 assimilation rate with growth at elevated [CO2] was 39%, despite a 40% decrease in stomatal conductance and a 11% decrease in Rubisco [ribulose-bisphosphate carboxylase] activity. Increased leaf CO2 uptake combined with an 18% stimulation in leaf area to provide a 59% increase in canopy photosynthetic rate. The increase in total dry weight was lower at 37%, and seed yield still lower at 24%. This shows that even in an agronomic species selected for maximum investment in seed, several plant level feedbacks prevent additional investment in reproduction, such that yield fails to reflect fully the increase in whole plant carbon uptake. Large soil containers (>9 litres) have been considered adequate for assessing plant responses to elevated [CO2]. However, in open-top chamber experiments, soyabeans grown in large pots showed a significant threefold smaller stimulation in yield than soyabeans grown in the ground. This suggests that conclusions about plant yield based on pot studies, even when using very large containers, are a poor reflection of performance in the absence of any physical restriction on root growth. This review supports a number of current paradigms of plant responses to elevated [CO2]. Namely, stimulation of photosynthesis is greater in plants that fix N and have additional carbohydrate sinks in nodules. This supports the notion that photosynthetic capacity decreases when plants are N-limited, but not when plants have adequate N and sink strength. The root:shoot ratio did not change with growth at elevated [CO2], sustaining the charge that biomass allocation is unaffected by growth at elevated [CO2] when plant size and ontogeny are considered.

Item Type: Article
Author Affiliation: Department of Crop Sciences, University of Illinois, 190 Edward R. Madigan Laboratory, 1201 W. Gregory Drive, Urbana, IL 61801, USA
Subjects: Plant Physiology and Biochemistry > Plant Physiology
Plant Physiology and Biochemistry > Biochemistry
Divisions: Soyabean
Depositing User: Syamala
Date Deposited: 27 Oct 2010 04:46
Last Modified: 27 Oct 2010 04:46
Official URL: http://dx.doi.org/10.1046/j.1365-2486.2002.00498.x
URI: http://eprints.icrisat.ac.in/id/eprint/301

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