The application of plant growth regulators to improve phytoremediation of contaminated soils: A review

Soil contamination is one of the most important environmental problems around the world. The transfer of organic contaminants and heavy metals to the food chain is a major threat to human health. Purging these contaminants often involves a lot of energy and complex engineering processes. Phytoremediation technology can be used in various environments, such as water, soil, and air, to reduce or eliminate different contaminants. The major mechanisms involved in phytoremediation include plant extraction, rhizofiltration, plant evaporation, plant stabilization, plant decomposition, and rhizosphere degradation. The efficiency of phytoremediation can be increased through using chelating and acidifying agents, applying electric current in the soil, using organic chemicals and fertilizers, planting transgenic plants, using bacteria, and applying plant growth regulators. Recently, the use of plant growth regulators has been investigated as a suitable method for improving the efficacy of phytoremediation. Effective plant growth regulators to improve phytoremediation include auxins, gibberellins, cytokinins, and salicylic acid. The activity of these materials depends on their concentration, environmental factors that affect their absorption, and the physiological state of the plant. Using these materials increases the biomass of the plant and reduces the negative effects of the presence of contaminants in the plant. The present study aimed to review the latest studies performed on the improvement of phytoremediation using plant growth regulators and their mechanisms. (C) 2018 Elsevier Ltd. All rights reserved.