ABSTRACT
Sulphur dioxide (SO2) is mainly emitted into the atmosphere from both natural (e.g., oxidation of dimethyl sulphate, volcanic eruption) and anthropogenic sources (mainly combustion of fossil fuel). The atmospheric level of SO2 has increased as a distinct air pollutant; therefore, plants are being faced with higher levels of SO2 throughout the world. Like other crop plants, SO2 also affects medicinal plants’ growth, bioactive constituents, and production. The duration and intensity of SO2 exposure decide its acute or chronic effects on medicinal plants. SO2 exposure influences several leaf characteristics, such as leaf production, leaf area, and photosynthetic pigments. SO2 exposure also decreases soluble sugar levels while the levels of ascorbic, proline, and amino acid are increased. The photosynthetic mechanism is disrupted by exposure to SO2. Additionally, SO2 accelerates the opening of stomata which leads to loss of water from the plant. Other common effects of SO2 exposure are noticed such as the reduction of overall biomass and respiration rate. They have also shown genotoxicities and disturbance in the production of some secondary metabolites. SO2 also affects the species composition at different ecosystem levels by replacing highly sensitive species that causes a decrease in productivity at the primary level. It also changes the tropic relationship of plant, animal, and microbial population. SO2 also in the form of acid rain (sulphuric acid) washes out the soils and plant nutrients. The acidic run-off also alters the water pH as well as dissolving a huge amount of nutrients in the water that creates problems in aquatic flora and fauna. The main aim of Chapter 4 is to consolidate and critically examine the impact of SO2 exposure on the growth performance, productivity, and active constituents of some medicinal plants.
