Effects of elevated CO 2 on leaf area dynamics in nodulating and non-nodulating soybean stands
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Effects of elevated CO2 on leaf area dynamics in nodulating and non-nodulating soybean stands Shimpei Oikawa & Masumi Okada & Kouki Hikosaka Received: 11 February 2013 / Accepted: 24 June 2013 # Springer Science+Business Media Dordrecht 2013
Abstract Aims The effects of elevated CO2 on leaf area index (LAI) vary among studies. We hypothesized that the interactive effects of CO2 and nitrogen on leaf area loss have important roles in LAI regulation. Methods We studied the leaf area production and loss using nodulating soybean and its non-nodulating isogenic line in CO2-controlled greenhouse systems. Results Leaf area production increased with elevated CO2 levels in the nodulating soybean stand and to a lesser extent in the non-nodulating line. Elevated CO2 levels accelerated leaf area loss only in nodulating plants. Consequently, both plants exhibited a similar stimulation of peak LAI with CO2 elevation. The accelerated leaf loss in nodulating plants may have been caused by newly produced leaves shading the lower
leaves. The nodulating plants acquired N throughout the growth phase, whereas non-nodulating plants did not acquire N after flowering due to the depletion of soil N. N retranslocation to new organs and subsequent leaf loss were faster in non-nodulating plants compared with nodulating plants, irrespective of the CO2 levels. Conclusion LAI regulation in soybean involved various factors, such as light availability within the canopy, N acquisition and N demands in new organs. These effects varied among the growth stages and CO2 levels. Keywords Leaf area index (LAI) . Leaf senescence . Legumes . Symbiotic N2-fixation . Nitrogen demand . Nitrogen retranslocation
Introduction Repsonsible Editor: Euan K. James. Electronic supplementary material The online version of this article (doi:10.1007/s11104-013-1826-6) contains supplementary material, which is available to authorized users. S. Oikawa (*) College of Science, Ibaraki University, Mito 310-0056, Japan e-mail: [email protected] M. Okada Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan K. Hikosaka Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan K. Hikosaka CREST, JST, Chiyoda, Tokyo 102-0076, Japan
The leaf area index (LAI: total leaf area per unit ground area) determines canopy photosynthesis and plant productivity by providing the potential for light interception. Previous experimental studies have demonstrated positive, neutral, or negative effects of CO2 on LAI as well as leaf area per plant, which depend on the species and experimental conditions (Cowling and Field 2003; Ainsworth and Long 2004; Körner et al. 2005). Pritchard et al. (1999) compiled 63 studies that examined CO2 responses in herbaceous and woody species. Of these, 57 % reported increased LAI and leaf area per plant with CO2 elevation, 10 % showed decreased leaf area, and 25 % showed no change. In the remaining cases, CO2 interacted with other environmental factors. Therefore, the effects of elevated CO2 on the LAI remain unclea
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