Effect of fluoride on photosynthesis, growth and accumulation of four widely cultivated rice (Oryza sativa L.) varieties in India.

Fluorine, one of the most abundant elements found on earth, acts as an environmental xenobiotics even at sparingly low concentrations. Uncontrolled anthropogenic activities have steeply increased the F content in the air, water, and soil. Irrigation of crops and vegetables with F contaminated groundwater or agricultural practices in contaminated soils adversely affect their physiological and biochemical parameters, leading to inhibited growth and productivity. Some plants can translocate the toxic ions from roots to shoots and accumulate them in the edible parts. Bioaccumulations of F have hazardous outcomes, as their concentrations in edible parts can be higher than the safe value. Screening of F hyperaccumulators and F-tolerant plants has been performed to facilitate phytoremediation. Some plant bioindicators have been identified which can be used to analyse the extent of atmospheric F pollution. Cumulative use of these organisms through proper scientific planning programs can potentially improve the agricultural soil quality in terms of their toxic F content. Future research should focus on proper execution of these phytoremediative strategies via robust field trials. High throughput genetic analyses should also be performed to identify quantitative trait loci which can be exploited to generate F-tolerant characters in susceptible crop cultivars.

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Fluorine: a biohazardous agent for plants and phytoremediation strategies for its removal from the environment

Fluoride pollution is now recognized as a global problem. The reason fluorides are considered as serious contaminants even when they are present at low levels is that they persist for a long time in air, soil, and water and exert negative effects at all levels of an ecosystem. Thus, immediate attention is the need of the hour to remediate the environment from F pollution. Till date, the conventional methods have been developed primarily to remove F from water. These methods are very slow and expensive. Besides, not much research has been done so far to remediate F from soil. This review focuses on the uptake and accumulation of F by certain aquatic and land plant species. Exploring these plants by analysis of their tissues for accumulated contaminants may open up several opportunities to be utilized to remediate F rich water and soil.

Accumulation of Fluoride by Plants: Potential for Phytoremediation

The research was based on a pot experiment, in which the response of eight species of crops to soil contamination with fluorine was investigated. In parallel, some inactivating substances were tested in terms of their potential use for the neutralization of the harmful influence of fluorine on plants. The response of crops to soil contamination with fluorine was assessed according to the volume of biomass produced by aerial organs and roots as well as their content of N-total, N-protein, and N-NO3-. The following crops were tested: maize, yellow lupine, winter oilseed rape, spring triticale, narrow-leaf lupine, black radish, phacelia, and lucerne. In most cases, soil pollution with fluorine stimulated the volume of biomass produced by the plants. The exceptions included grain and straw of spring triticale, maize roots, and aerial parts of lucerne, where the volume of harvested biomass was smaller in treatments with fluorine-polluted soil. Among the eight plant species, lucerne was most sensitive to the pollution despite smaller doses of fluorine in treatments with this plant. The other species were more tolerant to elevated concentrations of fluorine in soil. In most of the tested plants, the analyzed organs contained more total nitrogen, especially aerial organs and roots of black radish, grain and straw of spring triticale, and aerial biomass of lucerne. A decrease in the total nitrogen content due to soil contamination with fluorine was detected only in the aerial mass of yellow lupine. With respect to protein nitrogen, its increase in response to fluorine as a soil pollutant was found in grain of spring triticale and roots of black radish, whereas the aerial biomass of winter oilseed rape contained less of this nutrient. Among the analyzed neutralizing substances, lime most effectively alleviated the negative effect of soil pollution with fluorine. The second most effective substance was loam, while charcoal was the least effective in this respect. Our results showed the effect of soil contamination with fluorine on the yield and chemical composition of fluorine depended on the species and organ of a tested plant, on the rate of the xenobotic element and on the substance added to soil in order to neutralize fluorine.

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Effect of soil contamination with fluorine on the yield and content of nitrogen forms in the biomass of crops

Higher level of fluoride in underground water is a burning problem in many parts of the world. Continuous ingestion of fluoride containing water leads to fluorosis. In the present work, natural banana (Musa acuminate) peel (NBP), an unconventional adsorbent, has been explored for removal of fluoride from aqueous system. The NBP was characterized by using SEM, FTIR, and point of zero charge. In the batch study, maximum fluoride removal was achieved at the pH 4.0 (pHZPC 5.63), taking about 60 min to attain equilibrium. Kinetics data were fitted with a pseudo-second-order (R
 2 = 0.99) and Bahangam models (R
 2 = 1.00). The experimental data fitted well to a D-R adsorption isotherm (R
 2 = 0.995). Thermodynamic data suggests that the adsorption of fluoride on NBP is an exothermic reaction. Therefore, the results suggest that natural banana peel dust could be a cost-effective, eco-friendly adsorbent for removal of fluoride from aqueous medium.

https://link.springer.com/content/pdf/10.1007%2Fs41101-016-0015-x.pdf

Natural Banana ( Musa acuminate ) Peel: an Unconventional Adsorbent for Removal of Fluoride from Aqueous Solution through Batch Study

The influence of 0, 0.1 mM, 0.5 mM, 1.0 mM, 4.0 mM, 8.0 mM fluoride (F) concentration on seed germination, seedling growth of gram seeds (cv. Anuradha) was studied under laboratory condition. At the end of 15 days of treatment, significant reduction in root length, shoot length, dry weight, fresh weight, % of germination, protein content, catalase activity, tolerance index, vigour index, germination rate, germination relative index, mean daily germination were observed at increasing fluoride concentration. Total soluble sugar content, proline content, peroxidase activity, ascorbic acid oxidase activity, % DFC, % phytotoxicity of root and shoot increased along with gradual increment of F concentration. 4.0 mM F concentration was found to be most sensitive for gram seeds. At 8.0 mM F concentration germination occurred but plants were totally dried after completion of treatment period.

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Studies on the impact of fluoride toxicity on germination and seedling growth of gram seed (Cicer arietinum L. cv. Anuradha)

An assessment was undertaken to study the efficacy of bacterial consortia isolated from different sources viz rhizosphere of rice plant, oil spill sites of a petrol pump and from the sludge of a pharmaceutical waste water drain against the impact of fluoride The experiments were conducted with two crops In this mung bean experiment Vigna radiata was selected as a test crop The seeds were sown in the field with bacterial consortia, compost and reduced dose (25% less nitrogen than recommended dose) of chemical fertilizer After 30days of seed sowing (DAS), plants were collected from the field and dipped into the sodium fluoride solution with different concentrations for 48 hours Thereafter, the impact of fluoride on chlorophyll, sugar, proline and relative water content (%) were evaluated Scanning electron microscopy (SEM) of the stem section was performed SEM studies revealed that anatomical structure deformed with 15 mg/l sodium fluoride solution It was observed that such treatment combination during the sowing of crops leads to combat the impact of lower doses of sodium fluoride (02 mg/l) Another experiment was also conducted within plastic pots with and without bacterial consortia isolated from rhizosphere of rice plant and oil spilled soil of petrol pump with the same field soil Each pot was filled with 5 kg of soil + 2lt of water (on the basis of soil saturation) Oryza sativa seedlings were transplanted with different strength of sodium fluoride solution (25 mgNaF/kg, 50 mgNaF/kg, 100 mgNaF/kg and 500mgNaF/kg) within the above pots In second experiment, rice plants dried in all pots after 500 mgNaF/kg concentration of sodium fluoride In this pot experiment bacterial strain are capable of reducing fluoride content in soil as noted by measuring fluoride in the pot soil after the

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A. Maitra

Papers

Studies on the impact of fluoride toxicity on germination and seedling growth of gram seed (Cicer arietinum L. cv. Anuradha)

Amelioration of Fluoride Toxicity with the Use of Indigenous Inputs