Influence of elevated CO2 and ozone on enzymes related to photorespiration in soybean

To assess the effects of elevated carbon dioxide and ozone - applied alone and in combination - on plant photorespiration, soybean plants were exposed in open-top chambers in Raleigh, North Carolina, USA. Sequential harvests of leaf material were carried our 27 35, 50, 64, 78, 91 and 105 days after sowing. The activity of the photorespiration related enzymes glycolate oxidase and hydroxypyruvate reductase and the content of soluble proteins were measured. The content of soluble proteins were unaffected by all air treatments. The activity of glycolate oxidase and hydroxypyruvate reductase was inhibited significantly by CO2 and ozone up to 15 - 30% when compared with plants in charcoal filtered air and ambient CO2 concentrations. These results indicate a strong inhibitory effect of both gases - CO2 and ozone - on plant photorespiration which might have implications for nitrogen cycling and distribution in soybeans.