[Effects of elevated ozone concentrations on enzyme activities and organic acids content in wheat rhizospheric soil.]

The elevated concentration of tropospheric ozone (O3 ) is an important global climate change driver, with adverse impacts on soil ecological environment and crop growth. In this study, a pot experiment was carried out in an open top chamber (OTC), to investigate the effects of elevated ozone concentration on soil enzyme activities (catalase, polyphenol oxidase, dehydrogenase and invertase), organic acids contents (oxalic acid, citric acid and malic acid) at different growth stages (tillering, jointing, heading and ripening stages) of wheat, and combined with the rhizospheric soil physicochemical properties and plant root characteristics to analyze the underlying reasons. The results showed that, elevated ozone concentration increased soil catalase, polyphenol oxidase, dehydrogenase and invertase activities at wheat ripening period to different degrees, with the effects on the activities of catalase and polyphenol oxidase being statistically significant. At the heading stage, activities of dehydrogenase and invertase were significantly increased by up to 76.7%. At the ripening stage, elevated ozone concentration significantly increased the content of citric acid and malic acid and redox potential (Eh) in rhizospheric soil, but reduced soil pH, electrical conductivity, total carbon and nitrogen. For root characteristics, elevated ozone concentrations significantly reduced the wheat root biomass, total root length and root surface area but increased the average root diameter.