Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2009
Publication Date: 1/1/2010
Citation: Feng, Z., Pang, J., Kobayashi, K., Zhu, J., Ort, D.R. 2010. Differential responses in two varieties of winter wheat to elevated ozone concentration under fully open-air field conditions. Global Change Biology. DOI: 10.111/j.1365-2486.2010.02184.x Interpretive Summary: Ozone in the atmosphere near the earth's surface is on the rise and portends a significant threat to crop production particularly in industrialized parts of the world where ozone concentrations are the highest. Modern high yielding wheat varieties can be among the most sensitive of major crop plants to ozone. This study was conducted in China where ozone poses an urgent threat to wheat production. Using technology that allows ozone concentrations to be raised in open air conditions over plots in wheat fields, this study investigated the impact of ozone levels predicted for 2050 on high yielding modern winter wheat varieties. The findings of this study reveal that some cultivars show significant tolerance to ozone. This work lays the foundation of future studies to determine the underlying mechanism of ozone tolerance in wheat.
Technical Abstract: Two modern cultivars (Yangmai16 (Y16) and Yangfumai 2 (Y2)) of winter wheat (Triticum aestivum L.) of almost identical phenology were investigated for impacts of elevated ozone concentration (E-O3) on physiological characters related to photosynthesis under fully open-air field conditions in China. The plants were exposed to E-O3 from the initiation of tillering to final harvest, with an enhancement ratio of 27% above the ambient ozone concentration (A-O3). Measurements of pigments, gas exchange rates, chlorophyll a fluorescence and lipid oxidation were made in three replicated plots throughout flag leaf development. In cultivar Y2, E-O3 significantly accelerated leaf senescence, as indicated by increased lipid oxidation as well as faster declines in pigment amounts and photosynthetic rates. The lower photosynthetic rates were due mainly due to non-stomatal factors, e.g.lower maximum carboxylation capacity, electron transport rates and light energy distribution. In cultivar Y16, by contrast, the effects of E-O3 were observed only at the very last stage of flag leaf ageing. Since the two cultivars had almost identical phenology and very similar stomatal conductance in the leaves before senescence, the greater impacts of E-O3 on cultivars Y2 than Y16 cannot be explained by differential ozone flux into the leaf.