Effect of acid rain on growth and physiological responses of wheat

Abstract

Acid rain, which is a wet form of gaseous air pollutants, is formed when air pollutants such as SO2, NO2, CO2 in the atmosphere combine with water vapor of clouds. With the increase of concentration of these pollutants, the amount of acid rain increases. Acid rain, which is the mixture of sulphuric, nitric and carbonic acids, results in some changes in the soil such as decrease in pH, uncommon nutrient liberation, increase of release of toxic metals and the decline in the fertility of soil. These impacts have negative effects on plants. In the present work wheat plants were irrigated and leaf sprayed with four treatments of acid rain which contain sulphuric and nitrics acids with the pH of 2.5, 3.5, 4.5, 5.6 for a period of 32 days, whereas, control plants were irrigated and leaf sprayed by normal water with a pH of 7.4. According to the results we have obtained, control plants in whole growth and physiological indexes were better than those plants treated by acid rains with the pH of 2.5 and 3.5. Moreover, the plants treated by acid rain with the pH of 4.5 and 5.6, were lower in other factors except photosynthetic rate, pigment content and carbohydrate content than control plants. Also acid rains with the pH of 2.5 and 3.5 caused white spots in both surfaces of leaf and tip and border atrophy.