Vol.:(0123456789) 1 3 Acta Physiologiae Plantarum (2018) 40:181 https://doi.org/10.1007/s11738-018-2754-0 REVIEW Insights into fuoride-induced oxidative stress and antioxidant defences in plants Ritika Sharma 1  · Rajinder Kaur 1 Received: 22 November 2017 / Revised: 24 August 2018 / Accepted: 14 September 2018 © Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków 2018 Abstract Fluoride is a common pollutant which occurs in various environmental matrices considered as one of the most phytotoxic pollutants. It is essential to the living organisms in trace quantities but at its higher concentration it becomes poisonous. Excess amount of fuoride in environment not only exerts its toxic efects on human beings and animals but also on plants. Toxicological impacts of fuoride on plants have been largely debated due to reduction of growth parameters, inhibition of metabolic activities and decreased photosynthetic activity. The signs of fuoride impacts on plants may be severe, acute or chronic and toxicity of fuoride depends on dose, frequency of exposure, duration and genotype of plant. This article over- views understanding of transport, uptake and fuoride accumulation in plants and provide insights into the fuoride-induced oxidative stress and regulatory mechanisms to cope up with it. The main objective of this article is to prospect new research avenues to unravel the mechanisms explaining fuoride toxicity in various plant species. Keywords Fluoride · Genotype · Oxidative stress · Toxicological impacts Introduction Fluorine (F) is the frst member of halogen family and is the most electronegative element. It gets combined with other elements and forms fuoride. Intake of food and water by the living organisms is the main source of their exposure to fuoride. The most relevant inorganic fuorides which are known for their toxicological impacts on the environment depending upon their concentration released are hydrogen fuoride, calcium fuoride, sulfur hexafuoride, sodium fuo- ride and silicofuoride. It is ubiquitously distributed in air, soil and water. Fluorides are released into air in gaseous form. Prior to fnal deposition on earth’s surface or being dissolved in water, fuorides can be transported over dis- tant areas through wind. Generally, fuorides are unable to persist in the atmosphere for a longer duration except sulfur hexafuoride (SF 6 ) which has residual time period of several 1000 years in atmosphere (Environmental Health Criteria for Fluorides 2002). Apart from this, fuoride concentrations in water can be above, at or below recommended levels (World Health Organization 2011). Fluoride concentrations in lakes and rivers are below 0.5 mg/L but concentrations exceed in groundwater mainly in mountainous and volcanic areas which is above 50 mg/L. Diferent types of rocks such as particularly alkaline volcanic, hydrothermal and sedimen- tary have higher concentrations of fuorine. Weathering of rocks dissolves fuorine in water as fuoride. Over 95% of total fuoride is the F − ion in most of the potable water sources and the most common complex here formed is mag- nesium–fuoride complex (MgF + ) (Ateria et al. 2015). In soils, fuoride forms complex with aluminium or calcium (Environmental Health Criteria for Fluorides 2002). Fluo- ride gets adsorbed more tightly to soil particles when the soil is slightly acidic in nature. Moreover, soils contain innumer- able fuoride containing minerals, viz amphiboles, apatites, mica, etc. During rainfall, water percolates through the soil profle to both open and confned aquifers which act as a source of fuoride contamination in ground water (Handa 1988). Human beings are susceptible to fuoride toxicity through intake of water and food containing fuoride more than Communicated by P. Wojtaszek. * Rajinder Kaur swab2002@yahoo.com 1 Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar, Punjab 143005, India