Changes in the ultrastructure of chloroplasts and mitochondria and antioxidant enzyme activity in Lycopersicon esculentum Mill. leaves sprayed with acid rain

The effects of simulated acid rain (AR) on the ultrastructure of chloroplasts and mitochondria as well as the antioxidant defence system were investigated in Lycopersicon esculentum Mill. leaves. Analyses carried out 0.5, 3.0, 24, 48, 72 and 96 h after a single spraying of AR (pH 1.8) indicated alterations in 13% of chloroplasts and 95% of mitochondria, at the end of experiment. Disturbances in the structure of these organelles were accompanied by changes in activities of catalase (CAT), ascorbate peroxidase (APx), superoxide dismutase (SOD), including CuZnSOD, glutathione peroxidase (GSH-Px) and glutathione transferase (GST). AR caused a decrease in GSH-Px and CAT activities starting 24 h after treatment but an increase in SOD and its izoenzyme CuZnSOD activities at 72 and 96 h. On the other hand, GST activity significantly increased at 0.5-3 and after 48-72 h while APx activity increased at all experimental times. These data suggest that high APx and GST activities in L. esculentum were not sufficient to protect mitochondria but they might have been sufficient to prevent ultrastructural damage of chloroplasts. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.