|Pritchard, Seth - COLLEGEE OF CHARLESTON|
|Ju, Zhenlin - AUBURN UNIVERSITY|
|Vansanten, Edzard - AUBURN UNIVERSITY|
|Qui, Jiansheng - LI-COR|
|Weaver, David - AUBURN UNIVERSITY|
|Rogers Jr, Hugo|
Submitted to: Australian Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 6, 2000
Publication Date: November 2, 2000
Citation: Pritchard, S.G., Ju, Z., Van Santen, E., Qui, J., Weaver, D.B., Prior, S.A., and Rogers, H.H. 2000. The influence of elevated CO2 on the activities of antioxidative enzymes in two soybean genotypes. Australian Journal of Plant Physiology 27:1061-1068. Interpretive Summary: Global atmospheric CO2 concentrations are increasing rapidly due to combustion of fossil fuels and changing land use. Little is known, however, about the effect of this atmospheric change on the ability of soybeans to withstand environmental stress. We found that soybeans growing in elevated CO2 produce fewer antioxidants than those growing in normal air. Antioxidants are molecules produced by plants when they are attacked by pathogens or subjected to heat or drought stress. This research suggests that exposure to elevated CO2 reduces environmental stress in soybean plants.
Technical Abstract: The objective of this study was to investigate the effects of elevated atmospheric CO2 on antioxidative enzymatic activities of two soybean (Glycine max) genotypes. Seeds of two near isogenic soybean genotypes (A and B) were grown in ambient (365 ppm) or elevated (720 ppm) [CO2] in open top field chambers for 61 days. Leaves were collected 40, 47, 54, and 61 days after planting, and antioxidative enzymatic activities assayed. Elevated CO2 caused significant reductions in the activities of superoxidase dismutase (SOD; EC 220.127.116.11), peroxidase (POD; EC 18.104.22.168), catalase (CAT; EC 22.214.171.124) ascorbate peroxidase (APOD, EC 126.96.36.199), glutathione peroxidase (GPOD, EC 188.8.131.52), and glutathione reductase (GR, EC 184.108.40.206) in both genotypes. The activities of dehydroascorbate reductase (DAR, EC 220.127.116.11) and monodehydroascorbate reductase (MDAR, EC 18.104.22.168) increased in genotype B, but decreased in genotype A under elevated CO2. Growth in elevated CO2 resulted in a decrease in rubisco activity and decreased rubisco, chlorophyll, carotenoids, and total soluble protein contents. Genotype B had significantly higher rubisco and chlorophyll contents, and higher SOD, CAT, and POD activities than genotype A when grown under ambient CO2. No genotypic differences, however, were noted for activities of rubisco and MDAR under ambient CO2. When grown under elevated CO2, genotype A had a higher chlorophyll content, higher activities in CAT, POD, APOD, and GR, lower rubisco contents, and lower DAR, MDAR, and SOD activities than genotype B. No significant differences in GPOD activity between genotypes under elevated CO2 were found. Results indicate that antioxidative enzymatic activities may decrease in a high-CO2 world.