Author
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ROBINSON, MICHAEL |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 5/25/2005 Publication Date: 7/16/2005 Citation: Robinson, J.M. 2005. Does prolonged exposure of soybean plants to elevated ozone cause inhibition and/or inactivation of the foliar ascorbic acid synthesis pathway enzymes, galactose dehydrogenase and galactono-1,4-dehydrogenase? [abstract]. Plant Biology 2005 Final Program. Paper No. 112. p.118. Interpretive Summary: Technical Abstract: Two major enzymes in the green plant leaf cell ascorbic acid (ASC) synthesis pathway are L-galactose dehydrogenase (GALDH) and the terminal enzyme, L-galactono-1,4-dehydrogenase (GLDH). The effect of chronic elevated O3 exposure on mature soybean leaflet GALDH and GLDH activities was estimated in vivo. Glycine max L., cv Essex and cv Forrest plants were grown from emergence during the summer in open-top chambers (OTCs) in the greenhouse. Control plants grew in carbon-filtered air (CF) having low O3 (approximately 24 ppb). Test plants grew in air having high O3 (approximately 77 ppb). At 40 d PE, leaflets of mature leaves were excised at the petiolules in petri dishes with pure H2O (control), 45 mM L-galactose (GAL), or 45 mM L-galactono-1,4-lactone (GL), and immediately allowed to incubate with the petiolules under solution for 60 min in the greenhouse, in the high sunlight. Leaflets were subsampled into liquid N2, and ASC and dehydroascorbate (DHA) were extracted and quantified. In leaflets of both CF-grown cultivars, GAL or GL, compared to the H2O controls, significantly increased leaflet ASC+DHA (ASCtot) level by 2-3 times. In leaflets of both O3-treated cultivars, GAL produced no significant increase in ASCtot. In leaflets of O3-treated cv Essex, GL did not increase ASCtot. In ozonated Forrest leaflets, GL produced a much smaller increase in ASCtot compared with CF control leaflets. Thus, mature leaflets of CF cultivars seem to possess active GALDH as well as active GLDH. GALDH in leaflet cells of both cultivars appeared to be inhibited and/or inactivated by chronic exposure to elevated O3. Chronic O3-treatment resulted in inhibition and/or inactivation of GLDH in cv Essex leaflet cells, but GLDH activity in cv Forrest leaflet cells was only partially inhibited and/or inactivated. |
