Morphological and biochemical changes in Azadirachta indica from coal combustion fly ash dumping site from a thermal power plant in Delhi, India

• Disposal and management of fly ash are a major ecosystem and environment problem.
• Fly ash disposal, greatly change dynamics and functions of natural ecosystems.
• Fly ash cause several changes in plant physiology, growth and biochemical processes of A. indica A. Juss.
• Fly ash causes oxidative stress in plants, and antioxidant enzymes could help against oxidative injury.

The foliar and biochemical traits of Azadirachta indica A. Juss from fly ash (FA) dumping site in Badarpur thermal power plant (BTPP) New Delhi, India was studied. Three different experimental sites were selected at different distances from the thermal power plant. Ambient suspended particulate matter (SPM) and plant responses such as leaf pigments (chlorophyll a, chlorophyll b, and carotenoids), total chlorophyll, net photosynthetic rate, stomatal index (SI), stomatal conductance (SC), intercellular carbon dioxide concentration [CO2]i, net photosynthetic rate (NPR), nitrogen, nitrate, nitrate reductase activity, proline, protein, reducing sugar and sulphur content were measured. Considerable reduction in pigments (chlorophyll a, chlorophyll b and carotenoids), and total chlorophyll was observed at fly ash dumping site. Fly ash stress revealed the inhibitory effect on Nitrate reductase activity (NRA), Nitrate, soluble protein, and reducing sugar content, whereas stimulatory effect was found for the stomatal index, nitrogen, proline, antioxidants and sulphur content in the leaves. Under fly ash stress, stomatal conductance was low, leading to declining in photosynthetic rate and increase in the internal CO2 concentration of leaf. Single leaf area (SLA), leaf length and leaf width also showed a declining trend from control to the polluted site. Antioxidant enzymes increased in leaves reflecting stress and extenuation of reactive oxygen species (ROS).