Submitted to: International Journal of Plant Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/16/2010
Publication Date: 11/26/2010
Publication URL: hdl.handle.net/10113/49772
Citation: Sicher Jr, R.C. 2010. Daily changes of amino acids in soybean leaflets are modified by C02 enrichment. International Journal of Plant Biology. 1:89-93. Interpretive Summary: How crops might respond to changes in atmospheric gases like carbon dioxide is a major concern to growers. The current study examined biochemical changes in wheat and soybean leaves in response to ambient and elevated carbon dioxide treatments. Various small nitrogen containing compounds differed between the two crop species. It was proposed that these small molecules may explain the different growth responses of soybean and wheat to elevated carbon dioxide treatments. These findings are of interest to plant scientists working in the area of climate change, biochemistry and in the field of genetic engineering.
Technical Abstract: The effects of CO2 enrichment on plant growth and on nitrogen partitioning were examined using soybean [Glycine max (L.) Merr. cv. Clark] leaflets and wheat leaves (Triticum aestivum L. cv. Oxen). Both species were grown from single seeds in matching controlled environment chambers. Continuous ambient CO2 partial pressures were from 38 to 40 Pa for both species and elevated CO2 was 68 to 70 Pa for soybean and 98 to 100 Pa for wheat. Total above ground biomass, total leaf area and specific leaf weight of soybean were increased 78%, 58% and 33%, respectively, in response to CO2 enrichment when measured 25 days after sowing. Total chlorophyll (a + b), but not total soluble protein, was 25% greater in third trifoliolate soybean leaflets in response to CO2 enrichment. These latter two parameters did not differ across CO2 treatments in wheat leaves. Diurnal variations of total soluble amino acids were observed in leaves of both species and these were unaffected by CO2 enrichment. Increases of total soluble amino acids during the photoperiod were eight-fold greater in wheat than in soybean leaves. Most individual soluble amino acids were unaffected by CO2 enrichment. However, glycine was lower in the elevated compared to the ambient CO2 treatment of both species. Aspartate was increased 20% by CO2 enrichment in soybean leaflets, partially offsetting changes in glycine. Glutamate and glutamine were the predominant free amino acids in wheat leaves. In contrast to wheat, asparagine was the principal free amino acid in soybean leaflets and glutamine was present in low levels in this species at all measurement times. We suggest that soybean normally avoids photosynthetic acclimation due to CO2 enrichment because amino acid metabolism in this species largely depends on asparagine rather than glutamine metabolism.