Effects of elevated CO2 on leaf area dynamics in nodulating and non-nodulating soybean stands
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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.
We studied the leaf area production and loss using nodulating soybean and its non-nodulating isogenic line in CO2-controlled greenhouse systems.
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.
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.
KeywordsLeaf area index (LAI) Leaf senescence Legumes Symbiotic N2-fixation Nitrogen demand Nitrogen retranslocation
We thank Meguru Inoue, Teruo Saito, Yukichi Satoh, and other members of NARCT, Chiho Kamiyama and Kay-May Miyagi of Tohoku University for technical assistance. Shoichiro Akao allowed us to use En1282. Makie Kokubun provided the seeds. We are also grateful to Elizabeth Ainsworth, Toshihiko Kinugasa and Toshinori Matsunami for comments. This work was supported by KAKENHI, a Grant-in-Aid for Young Scientists by Japan Society for the Promotion of Sciences (No. 23770027) and a Grant-in Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 21114001).
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