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

Most of leafy vegetables grow near cities and exhaust emission affects their morphological, physiologic and biochemical attributes of them. The experiment was conducted in a factorial experiment based on a completely randomized design with three replications in the greenhouse of the Isfahan University of Technology of Iran. Lettuce seedlings were exposed to exhaust emissions or pollution in three different exposure times (10, 20 and 30 days). Then, their morphological, physiological and biochemical traits were measured and compared with the control plants. Results showed that in plants that were exposed to pollution for 30 days, the catalase, ascorbate peroxidase, guaiacol peroxidase activity, proline content, electrolyte leakage, relative water content and the number of stomata significantly increased. It was observed that the photosynthetic factors, leaf area, plant height, shoot fresh and dry weight and length of stomata in lettuce plants decreased after 30 days, compared to the controls. The photosynthetic rate, stomatal conductance, CO2 intracellular concentration and leaf area of lettuce seedlings increased when exposed to emissions for 10 days. Generally, the results showed that the exposure of lettuce plants to pollution, especially after 30-days, caused more morphological (leaf area, plant height), physiological (catalase, ascorbate peroxidase, guaiacol peroxidase activity, proline content, electrolyte leakage, relative water content, photosynthetic rate, stomatal conductance, CO2 intracellular concentration) and anatomical (stomata density) changes due to contaminants.