Foliar Concentrations of Selected Elements, Assessment of Oxidative Stress Markers and Role of Antioxidant Defense System is Associated with Fly Ash Stress Tolerance in Withania somnifera

Increased dependence on thermal power has resulted in a significant increase in the generation of fly ash (FA), which exacerbates environmental pollution. In order to mitigate this source of pollution, we propose covering FA dumps with a layer of planted vegetation. Due to varying degrees of tolerance and their sessile nature, plants are themselves susceptible to stress from pollution. This suggests that an investigation to assess the role of wild growing plants for management of FA dumps, where selected wild plants could be grown to mitigate consequences of FA. The present study assesses oxidative damage and the foliar concentration of metals in Withania somnifera growing wild at the Badarpur Thermal Power Plant (BTPP) compared to those growing at a control site. Plants growing at the BTPP showed significantly higher foliar concentrations of Pb, Mn, and Fe, and low concentrations of Ni and Cd. The plants at the BTPP site showed signs of oxidative stress as indicated by enhanced levels of malondialdehyde and electrolyte leakage from cells. The CO₂ assimilation rate, net photosynthetic rate, rate of transpiration, stomatal conductance decrease, while water use efficiency, and air pollution tolerance index increase. Among air pollution tolerance index parameters, relative water content showed a significant increase with FA pollution stress at the BTPP. A significant decrease was observed in leaf morphology single leaf area, leaf length, and leaf width and biochemical parameters (Chlorophyll a, Chlorophyll b, total chlorophyll, and carotenoids. Moreover, FA pollution stress induces oxidative stress in W. somnifera through a significant and enhanced production of reactive oxygen species (ROS). According to our observations, the ability of W. somnifera to effectively coordinate superoxide dismutase, ascorbate peroxidase, and glutathione reductase activities involved in the scavenging of ROS along with the enhanced increment of nonenzyme activities (total ascorbic acid, proline, and oxidized glutathione) could be related to FA stress tolerance in W. somnifera.