Differential root responses in two cultivars of winter wheat ( Triticum aestivum L.) to elevated ozone concentration under fully open‐air field conditions

The effect of elevated tropospheric ozone concentration [O 3 ] on root processes in wheat systems of different O 3 sensitivity is not well understood. Two wheat cultivars (cv. Y15 and YN 19) with contrasting O 3 tolerance were grown in a fully open‐air O 3 enrichment platform for one season. We found that elevated O 3 ( EO 3 ) (50% above the ambient O 3 ) significantly decreased the total biomass at all key growth stages and the yield of the O 3 ‐sensitive cultivar YN 19 but did not affect those of the O 3 ‐tolerant cultivar Y15. EO 3 significantly decreased the root biomass of two wheat cultivars at the jointing and grain‐filling stages. EO 3 significantly decreased the root length, length density, surface area and volume of the two cultivars at the jointing stage but increased those of YN 19 at the grain‐filling stage. EO 3 significantly increased the root activities (specific root respiration rates) of Y15 and YN 19 at the jointing, heading and grain‐filling stages. EO 3 significantly decreased the contribution of fresh root respiration to soil respiration ( CRS ) of YN 19 at the jointing stage but increased it at the heading stage; however, it did not change the CRS of Y15 at any growth stages. This study indicates that the effects of EO 3 on root morphology and activity varied among wheat cultivars, and suggest that we can breed O 3 ‐tolerant cultivars to maintain crop yield under higher [O 3 ] scenarios.