Variations in leaf anatomical characteristics drive the decrease of mesophyll conductance in poplar under elevated ozone

Abstract

Decline in mesophyll conductance (gm) plays a key role in limiting photosynthesis in plants exposed to elevated ozone (O3). Leaf anatomical traits are known to influence gm, but the potential effects of O3‐induced changes in leaf anatomy on gm have not yet been clarified. Here, two poplar clones were exposed to elevated O3. The effects of O3 on the photosynthetic capacity and anatomical characteristics were assessed to investigate the leaf anatomical properties that potentially affect gm. We also conducted global meta‐analysis to explore the general response patterns of gm and leaf anatomy to O3 exposure. We found that the O3‐induced reduction in gm was critical in limiting leaf photosynthesis. Changes in liquid‐phase conductance rather than gas‐phase conductance drive the decline in gm under elevated O3, and this effect was associated with thicker cell walls and smaller chloroplast sizes. The effects of O3 on palisade and spongy mesophyll cell traits and their contributions to gm were highly genotype‐dependent. Our results suggest that, while anatomical adjustments under elevated O3 may contribute to defense against O3 stress, they also cause declines in gm and photosynthesis. These results provide the first evidence of anatomical constraints on gm under elevated O3.

The combined application of ethylenediurea and arbuscular mycorrhizal fungi alleviates ozone damage to Medicago sativa L

“…Tropospheric ozone (O 3 ) is a secondary pollutant, as it originates from the photochemical reaction of precursor substances, such as nitrogen oxides and volatile organic compounds (Wang et al, 2017b), and is phytotoxic (Wittig et al, 2009). O 3 infiltrates plants through their stomata, causing cell structure destruction, reduced photosynthetic capacity (Xu et al, 2023), decreased biomass (Wang et al, 2021), and disruptions to the overall ecosystem functioning (Hayes et al, 2007). Some meta-analyses showed that the current O 3 concentration reduced the biomass of poplars by 4% (Feng et al, 2019a), and reduced the biomass of woody plants by 7% (Wittig et al, 2009).…”