EFFECTS OF EXPOSURE TO AIR POLLUTANTS SO2 AND NO2 ON TOMATO (Lycopersicon esculentum) LEAVES

ABSTRACT

This study evaluated the effects of exposure to air pollutants SO2 and NO2 on tomato (Lycopersicon esculentum) leaves. Three week and four week old plants of Lycopersicon esculentum were exposed to SO2 and NO2 gases generated by chemical reaction into a chamber for one hour. The plants were exposed after generation on the first day and repeated the following day for 6 hours. The concentrations of SO2 and NO2 measured in the chambers before plant exposure were 133.3 ppm and 126.6 ppm. The results obtained showed a decrease in the activities of stress enzymes (CAT, SOD and POX) as compared to control. Catalase contents of Lycopersicon esculentum exposed to NO2 showed a reduction in the 3 week old plants, compared to control which showed appreciable retention (84.31±2.56 and 98.59±4.70) (50.52±1.74 and 91.84±7.12).Young leafy Lycopersicon esculentum plants exposed to NO2 showed a slight reduction in superoxide dismutase content during the 3 week exposure of the plants compared to control (1.77 ± 0.01 and 1.78 ± 0.01) (1.13 ± 0.03 and 1.71 ± 0.01). Similar trend was also observed during exposure of the 4 week plants to NO2. A slight reduction was seen during exposure of the plants to SO2 compared to NO2. Morphological conditions such as leaf browning, chlorosis and shrinkage of leaves were also observed. It is apparent that the plants exposed to elevated SO2 and NO2 gases did not exhibit sufficient capacity to counteract the stress imposed by the gases. Morphological notes showed that Lycopersicon esculentum exhibited more dehydration effects compared to during plant exposure to SO2 and NO2 gases.