in vivo analysis of the effect of season-long open-air elevation of ozone to anticipated 2050 levels on photosynthesis in soybean

• Published in: Plant physiology (Bethesda) 2004-08, Vol.135 (4), p.2348-2357
• Main Authors: Morgan, P.B, Bernacchi, C.J, Ort, D.R, Long, S.P
• Format: Article
• Language: English
• Subjects: air pollution; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Carbon dioxide; drug effects; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Electron Transport; Environmental Stress and Adaptation; filling period; Fluorescence; Forecasting; Fundamental and applied biological sciences. Psychology; Glycine max; Glycine max - drug effects; Glycine max - physiology; Growing seasons; Illinois; Leaves; metabolism; Non agrochemicals pollutants; Ozone; Ozone - metabolism; Ozone - pharmacology; P values; pharmacology; Photosynthesis; Photosynthesis - drug effects; Photosynthesis - physiology; physiology; Phytopathology. Animal pests. Plant and forest protection; Plant Leaves; Plant Leaves - drug effects; Plant Leaves - physiology; Plants; pollutants; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; Seasons; Soybeans; Tillage
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.043968

Rising atmospheric carbon dioxide concentration ([CO2]) is widely recognized, but less appreciated is a concomitant rise in tropospheric ozone concentration ([O3]). In industrialized countries, [O3] has risen by 0.5% to 2.5% per year. Tropospheric [O3] is predicted to reach a global mean of >60 nL L-1 by 2050 with greater averages locally. Previous studies in enclosures suggest that this level of [O3] will decrease leaf photosynthesis, thereby limiting growth and yield of Glycine max L. Merr. SoyFACE (Soybean Free Air gas Concentration Enrichment) is the first facility to elevate atmospheric [O3] (approximately 1.2x current) in replicated plots under completely open-air conditions within an agricultural field. Measurements of gas exchange (assimilation versus light and assimilation versus intercellular [CO2]) were made on excised leaves from control and treatment plots (n = 4). In contrast to expectations from previous chamber studies, elevated [O3] did not alter light-saturated photosynthesis (Asat, P = 0.09), carboxylation capacity (Vc,max, P = 0.82), or maximum electron transport (Jmax, P = 0.66) for the topmost most recently fully expanded leaf at any stage of crop development. Leaves formed during the vegetative growth stage did not show a significant ozone-induced loss of photosynthetic capacity as they aged. Leaves formed during flowering did show a more rapid loss of photosynthetic capacity as they aged in elevated [O3]. Asat, Vc,max, and Jmax (P = 0.04, 0.004, and 0.002, respectively) were decreased 20% to 30% by treatment with ozone. This is noteworthy since these leaves provide photosynthate to the developing grain. In conclusion, a small (approximately 20%) increase in tropospheric [O3] did not significantly alter photosynthetic capacity of newly expanded leaves, but as these leaves aged, losses in photosynthetic carbon assimilation occurred.