Ozone Induced Injury to Cellular Membranes in Triticum aestivum L. and Protection by the Triazole S-3307

Seven day old wheat plants (Triticum aestivum L.), cv. Fredrick, were exposed to an ozone atmosphere of 0.5 ppm for a period of 6 h. The leaves of the control plants showed typical symptoms of ozone injury, i.e. chlorosis, necrotic lesions, increased solute leakage and reduced Hill activity. These phytotoxic symptoms were prevented in the plants grown from seeds which had been treated at 0.03 g.kg−1 seed with the triazole S-3307. Ozone treatment also induced a decline in phospholipid content and a concomitant increase in the concentrations of free fatty acids. There was no evidence of fatty acid peroxidation in that there was no significant decrease in fatty acid unsaturation with ozone fumigation. This supports the hypothesis that the mechanism of ozone toxicity may be partially mediated through a free radical cleavage of the ester linkages between the glycerol moiety and the fatty acid tails of phospholipids. The cleavage of phospholipids was not evident in the plants pretreated with S-3307 and it is suggested that this may be due in part to increases in lipid soluble antioxidants found in the triazole treated plants.