Growth and antioxidant responses in plants induced by heavy metals present in fly ash

Fly ash (FA) is a solid waste generated from coal combustion processes every year from thermal power plant. FA was considered as a problem for the environment, but also proves to be beneficial for the agricultural crops. This review begins with the utilization of FA as a soil ameliorant, its role in enhancing the plant growth and impact of elemental uptake from FA on plant growth. FA improves the physical, chemical and biological property of the soil which thereby enhances the crop productivity. Then, it focusses on phytotoxicity of various heavy metals in plants such as chromium, arsenic, lead, zinc, etc., followed by analyzing the defense mechanism of the plants against these heavy metal stresses which is due to the presence of toxic heavy metals present in FA resulting in the generation of reactive oxygen species which further causes oxidative stress. Finally, the review analyzes the influence of heavy metals on the antioxidative system of various plant species which helps in understanding the usage of optimum concentration of FA amendment in the soil for plant cultivation and to further explore the key features regulating the heavy metal damage and utilization of FA in agriculture.