Intercellular BVOC accumulation reflects sustainedantioxidant defenses without additional carbon loss underozone exposure in Eugenia uniflora

Tropospheric ozone (O) is a major atmospheric pollutant that affects plant carbon metabolism, redox homeostasis, and secondary metabolism, including the biosynthesis and emission of biogenic volatile organic compounds (BVOCs). However, the contribution of BVOCs to O3 tolerance, particularly in tropical woody species, remains poorly understood. Here, we investigated whether acute O exposure (cumulative AOT40 of 3497.82 ppb h) induces alterations in photosynthetic performance, redox homeostasis, and BVOC partitioning in Eugenia uniflora. We evaluated gas exchange, photosynthetic pigments, ascorbate and glutathione pools, emitted BVOCs, modeled intercellular BVOC concentrations, and the relative carbon cost associated with BVOC emissions. O exposure significantly increased net CO2 assimilation without affecting stomatal conductance, transpiration, leaf water status, or chlorophyll concentrations, indicating maintenance of photosynthetic performance. Carotenoid concentrations and total glutathione decreased, whereas glutathione redox status was maintained. O induced marked compound-specific changes in BVOC composition and partitioning. Several monoterpenes appeared exclusively under O exposure, {gamma}-elemene emission increased significantly, and the relative distribution of individual BVOCs between the modeled intercellular and emitted pools was altered. These findings show that the response of E. uniflora to acute O exposure was characterized by interplay among carbon assimilation, glutathione redox regulation, and BVOC partitioning rather than by increased total volatile emission. Enhanced carbon assimilation occurred without additional carbon loss through BVOC release, while changes in the modeled intercellular pool indicate that part of the volatile response remained within the leaf. Our findings highlight BVOC partitioning as an important dimension of the plant response to oxidative stress and demonstrate that emission measurements alone may not fully capture the fate and potential physiological role of volatile carbon under O exposure. O_FIG O_LINKSMALLFIG WIDTH=178 HEIGHT=200 SRC="FIGDIR/small/743946v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@1383d19org.highwire.dtl.DTLVardef@1333909org.highwire.dtl.DTLVardef@1e5a471org.highwire.dtl.DTLVardef@18efede_HPS_FORMAT_FIGEXP M_FIG C_FIG BVOC Partitioning Contributes to Oxidative Stress Defence Under Acute O Exposure