Responses of Plants to Fluoride: an Overview of Oxidative Stress and Defense Mechanisms

The fluoride ion (F) is widespread in the environment and toxic for all living organisms. Prolonged exposure to F leads to physiological, biochemical, and molecular modifications in plants. F is known as a potential metabolic inhibitor, interfering with the overall responses of plants including seed germination, growth and productivity, biomass accumulation, photosynthesis, enzyme activities, protein synthesis, gene expression patterns, and reactive oxygen species (ROS) production. It has also been shown to amend the functionalities of various antioxidants leading to oxidative stress inside plants. However, in recent years, a few attempts have been made to mitigate the ill effects of F on plants and their productivity responses. Modulation of cellular thiol molecules for protection against ROS-induced injury has been considered to be one of the effective strategies against F toxicity. In addition, the accumulation of proline and exogenous supplementation with salicylic acid have been shown to be potential measures for protecting the plants from F toxicosis. The present review covers the information available so far on the mechanism(s) of F uptake by plants, the F-induced physiological, biochemical, and molecular amendments in plants, and the potential for mitigation of F-stress in plants by using various molecules. The authors have also attempted to highlight the gaps in the existing knowledge for F toxicity in plants and the future research prospects.