Azolla for agro-environmental sustainability

The increasing industrialization, road and air transport, and intensive agriculture practices to meet the demands of a growing population have become a threat to the environment globally. The utilization of agrochemicals in an inappropriate way to enhance productivity has depleted the soil fertility, and biodiversity and negatively affected the climate. Keeping in view the present scenario, adoption of sustainable, economically and socially viable approaches are of utmost importance. Azolla is a free floating fern of great potential as a step towards achieving agro-environmental sustainability. Carbon neutral system has been the need of the day. Various species of Azolla have been reported from tropical and subtropical areas of the world. The symbiotic association of Azolla with nitrogen fixing blue green alga, Anabaena is an important co-evolved system and important contributor to biotechnological fields. Along with biological nitrogen fixation, cyanobacteria and Azolla promote plant growth as their extract contains different plant growth-promoting substances such as auxins, cytokinins, and gibberellins. Different species of Azolla play an amazing role for plant growth promotion as biofertilizers and for amelioration of abiotic stress. The use of Azolla is thus an innovative technology towards clean and green environment as they can sequester a lot of carbon dioxide in their bodies. The present review deals with diversity, distribution, and biotechnological applications of Azolla in different sectors, including agriculture, industry, and the environment.