Liriodendron tulipifera was exposed to gradually elevated ozone concentrations of 100-300 μg kg-1 in the naturally irradiated environment chamber. During 15 d of exposure to O3, net photosynthetic rate (PN) decreased and there was large difference between the control (C) and treatment with ozone (OT), while there was no significant difference in water use efficiency. Total chlorophyll content as well as the value of fluorescence parameter Fv/Fm decreased, while antioxidant enzyme activities related to ascorbate-glutathione cycle increased after 15 d of OT. Unchanged contents of ascorbate and glutathione indirectly suggest that the species hastened the antioxidant's oxidization/reduction cycle using enzymes instead of expanding their pool against oxidative stress. and S. Z. Ryang ... [et al.].
Plants of an Egyptian cultivar of wheat (Triticum aestivum L. cv. Giza 63) were exposed in open-top chambers (OTCs) for 8 h d-1 for up to 75 d to a factorial combination of two levels of salinity (0 and 50 mM NaCl) and two levels of O3 (filtered air and 50 mm3 m-3). Exposure to 50 mm3 m-3 O3 significantly decreased stomatal conductance (gs), net photosynthetic rate (PN), and chlorophyll (Chl) content by 20, 25, and 21 %, respectively. This reduction resulted in a change in assimilate allocation in favour of shoot growth leading to a decrease in root to shoot ratio and eventually to a decrease in relative growth rate (RGR) of both root and shoot. There was a very large reduction in yield parameters, especially in the number of ears/plant and 1 000-grain mass. Soil salinity significantly reduced PN and gs by 17 and 15 %, respectively, while Chl content was increased by 17 %. Root growth was decreased leading to an increase in root/shoot ratio. Yield parameters were decreased due to salt stress. There was antagonistic interaction between salinity (50 mM NaCl) and O3 (50 mm3 m-3) showing that salinity effectively protects against the adverse effects of O3 by increasing gs during O3 fumigation.