Effect of air pollution resulting from exhaust emission on the morphological, physiologic and biochemical responses of lettuce (Lactuca sativa var. longifolia)

The experiment was conducted in factorial test based on a completely randomized design with three replications in greenhouse of Isfahan University of Technology of Iran. Lettuce seedlings were exposed separately to the exhaust emissions in three different exposure times (10, 20 and 30 days) and after the exposure time, their morphological, physiological and anatomical traits were measured and compared with morphological, physiological and anatomical traits of control plants. Results obtained in lettuce, showed significant increases in traits including catalase, ascorbate peroxidase, guaiacol peroxidase, proline, electrolyte leakage, relative water content and number of stomata and significant decreases in photosynthetic factors, leaf area, height, aerial fresh and dry weight and length of stomata in lettuce plants which were exposed to gases for 30 days, compared to controls. Significant increase in the photosynthetic rate, stomatal conductance, CO2 intracellular concentration and leaf area of lettuce seedlings were exposed to emissions for 10 days, most likely, indicate the nutritional role of output gases from generator in the short period time of exposure. It was observed that the anatomical features of contaminated samples have been changed by gases in 30-days exposure plants compared to others. The results showed that the exposure of lettuce plants to gases, especially 30-days exposure, caused morphological, physiological and anatomical reactions due to contaminants that could be considered these reactions as the adaptation of these plants to the stress of contamination, in order to adapt or to deal with stress conditions and thus to survive the plant under pollution stress conditions.