Environ Sci Pollut Res DOI 10.1007/s11356-017-8424-8
SHORT RESEARCH AND DISCUSSION ARTICLE
Phytoremediation of fluoride with garden ornamentals Nerium oleander, Portulaca oleracea, and Pogonatherum crinitum Rahul V. Khandare 1 & Shaileshkumar B. Desai 1 & Sourabh S. Bhujbal 1 & Anuprita D. Watharkar 2 & Shivtej P. Biradar 2 & Pankaj K. Pawar 2 & Sanjay P. Govindwar 2
Received: 9 August 2016 / Accepted: 6 January 2017 # Springer-Verlag Berlin Heidelberg 2017
Abstract Nursery grown plants of Nerium oleander, Pogonatherum crinitum, and Portulaca oleracea were observed to remove fluoride up to 92, 80, and 73%, respectively, from NaF solution at the concentration of 10 mg L−1 within 15 days. Concentration range of 10–50 mg L−1 of fluoride revealed a constant decrease of removal from 92 to 51% within 15 days by N. oleander, while the biomass (one to five plants) showed enhancement in removal from 74 to 98% in 10 days. Translocation and bioaccumulation factors calculated after fluoride contents in roots and leaves of N. oleander, P. crinitum, and P. oleracea were 1.85, 1.19, and 1.43, and 9.8, 3.6, and 2.2, respectively. P. oleracea, P. crinitum, and N. oleander showed reductions in chlorophyll contents by 40, 57 and 25 and 8%, carbohydrates by 50, 44, and 16%, and proteins by 38, 53, and 15%, respectively. Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) in the roots of P. oleracea, P. crinitum, and N. oleander were observed to be induced by 400, 383, and 500%; 80, 105, and 424%; and 153, 77, and 71%, respectively, while the leaves showed induction in SOD, CAT, and GPX activities by 550, 315, and 165%; 196, 227, and 243%; and 280, 242, and 184%, respectively. Results endorsed the
Responsible editor: Philippe Garrigues * Rahul V. Khandare
[email protected] * Sanjay P. Govindwar
[email protected] 1
Department of Biotechnology, Shivaji University, Vidyanagar, Kolhapur 416004, India
2
Department of Biochemistry, Shivaji University, Vidyanagar, Kolhapur 416004, India
superiority of N. oleander for fluoride removal over other plant species. Keywords Fluorides, toxicity . Nerium oleander . Bioaccumulation . Phytoremediation
Introduction Fluoride is widely distributed in soils and rocks in the ionic forms of fluorine. It is considered as both an essential and a pollutant at high concentrations that cause a number of disorders. In India, nearly 90 million people including 6 million children in 200 distinct territories in 17 states are affected with dental and/or skeletal and non-skeletal fluorosis (Sinha et al. 2000; Duraiswami and Patankar 2011). Additionally, fluoride ions may attack bones and cause dental and bone osteoporosis (Cooke et al. 1990). Although it is required for protection against dental caries and weakening of bones (Kumar 2011), the effects of excessive intake may lead to stiffness, rheumatism to permanent crippling, and kidney damage (Sivasamy et al. 2001). Fluoridated water is associated with osteosarcoma (bone cancer) in human males which is the third most common cancer in children with a death rate of 50% and most survivors lose limbs to amputation (Bassin et al. 2006). The World Health Organization advocates the permissible upper limit for fluoride in drinking water to be 1.5 mg L−1. However, high fluoride concentrations in groundwater (1–48 mg L−1) are found in the parts of Africa, Asia, China, India, Ghana, Kenya, Tanzania, Sri Lanka, and Rift Valley countries in Africa and the USA (Jagtap et al. 2012). Additionally, individual activities such as metal plating, coal mining, and semiconductor production also release fluorides in the environment (Paudyal et al. 2013). In view of these facts, it is highly
Environ Sci Pollut Res
desirable to work on the effective removal strategies to have a solution over fluoride contamination. Classically known defluoridation procedures mainly involve precipitation, adsorption, electrodialysis, ion exchange, electrocoagulation, membrane techniques, etc. (Mameri et al. 1998; Amor et al., 1998). These methods however possess limitations when magnitude of the problem and its in situ remediation are concerned. Moreover, they are costly and therefore are not affordable by the common people. Therefore, alternative strategies for fluoride removal needs to be worked out and employed. Phytoremediation has emerged as an economic and green technology for the treatment of environmental pollutants present at larger enormities. Heavy metals, radionucleoids, chlorinated biphenyls, pesticides, solvent, endocrine disrupting chemicals, textile dyes, and many other toxic compounds have been successfully removed with phytoremediation approaches (Khandare and Govindwar 2015). As far as phytoremediation of fluoride is concerned, Ceratophyllum demersum, Hydrilla verticillata, Potamogeton malaianus, Myriophyllum verticillatum, Elodea nuttallii (Zhou et al. 2012), Camellia sinensis (Ruan et al. 2003), Fraxinus pennsylvanica, Liriodendron tulipifera, Taxodium distichum, Salix Willow, Platanus sp., Salix nigra, etc. have earlier been explored for treatment of soil and leachates (Kang et al. 2008). This work was carried out on the notion that the plants are known to be relentlessly performing the removal of fluorides from environment. Consequently, searching efficient hyperaccumulator plants for fluoride removal would be an appreciable approach to have a solution over this natural contaminant. Plants with higher biomass and fibrous root systems could prove to be ideal remediation of fluorides from water. In the proposed work, garden ornamental plants such as Nerium oleander, Pogonatherum crinitum, and Portulaca oleracea have been studied and explored for the removal of fluoride from water. Use of ornamental plants would be an aesthetically pleasant mode of phytoremediation.
P. oleracea, Cascabela thevetia, Brassica oleracea, and Cosmos bipinnatus were collected from Sajeev Nursery, Kolhapur, India. Other plants namely Alocasia macrorrhizos, Typha angustifolia, Spirodela polyrhiza, and Lawsonia inermis were collected from the site of the Maharashtra Industrial Development Corporation, Kagal, India. Initial measurement of fluorides in roots and leaves of plants before experiment The plants roots were washed carefully under tap water treated with 0.1 M HgCl2 solution for 2 min and washed again with deionized water, and the leaves were also carefully rinsed. Two and a half grams (fresh weight) of root and stem and leaf (leaves from apical, medial, and basal regions) samples of N. oleander, P. crinitum, P. oleracea, A. macrorrhizos, T. angustifolia, S. polyrhiza, and L. inermis were independently homogenized in 2.5 mL deionized water and centrifuged at 4561×g for 5 min to obtain cell-free extracts. The fluoride concentrations in these samples were measured independently using the SPADNS reagent (APHA 1998). Screening of plant species for fluoride removal from water The fluoride solution of a concentration of 5 mg L−1 was prepared dissolving 11.5 mg of anhydrous NaF in 1 L deionized water. Plant roots were independently exposed to 200 mL of the solution in a 500-mL polypropylene Erlenmeyer flask. Looking at the initial fluoride removal performances of the plants (data not shown), N. oleander, P. crinitum, and P. oleracea were selected for further studies. Fluoride amounts of the solutions were checked spectrophotometrically by SPADNS method reported earlier (APHA 1998) at every 24 h during initial screening. Phytoremediation trials with selected plants, and effect of plant biomass and fluoride concentration on removal by N. oleander
Experimental Chemicals and plant materials Zirconium oxychloride, trisodium2-parasulfophenylazo-1,8dihydroxy-3,6-napthalene disulfonate (SPADNS) reagent, sodium arsenite, and sodium fluoride were purchased from Himedia Pvt. Ltd., Mumbai, India. Superoxide dismutase (SOD) assay kit (cat. no. 19160), catalase (CAT) assay kit (cat. no. CAT100), glutathione peroxidase (GPX) assay kit (cat. no. CGP1), 2′7′-dichlorofluorescin (H2DCF) (cat. no. D6883), and 4′,6-diamidino-2-phenylindole (DAPI) (cat. no. D9542) were procured from Sigma-Aldrich, USA. All the chemicals and reagent used were of highest purity and analytical grade available. Plants of N. oleander, P. crinitum,
For further studies, the roots of N. oleander, P. crinitum, and P. oleracea were further independently exposed to 200 mL fluoride solution prepared separately by dissolving 22.1 mg anhydrous NaF in 1 L deionized water attaining a concentration of 10 mg L−1 fluoride. The fluoride removal was monitored for 15 days over every 72-h interval. To check the effect of concentrations, different fluoride solutions at concentrations of 10, 20, 30, 40, and 50 mg L−1 were separately prepared and plants of only N. oleander with equal biomass were independently exposed to 200 mL fluoride solution in 500-mL Erlenmeyer flasks and fluoride removal from the solution was monitored for 15 days after every 72 h. To study the effect of plant biomass, one to five plants of equal growth were exposed independently to 200 mL fluoride
Environ Sci Pollut Res
solution at a concentration of 50 mg L−1. The fluoride removal from the solution was monitored after every 48 h for 10 days. Detection of fluoride in leaves and stem and subsequent analysis The fluoride concentrations in roots and leaf samples were also measured after phytoremediation experiments independently using the APHA protocol (1998) as mentioned in the BInitial measurement of fluorides in roots and leaves of plants before experiment^ section. The amount of fluoride accumulated in roots and leaves were calculated in milligrams per gram of the plant tissues. The fresh weights of the leaves that were considered for translocation factors were 10 ± 1.2, 8 ± 0.78, and 7 ± 0.82 g for N. oleander, P. crinitum, and P. oleracea, respectively. The translocation factor and bioaccumulation factor were calculated using the following equations. Translocation factor ¼
Amount of fluoride in leaves ðmg g−1 Þ Amount of fluoride in roots ðmg g−1 Þ
ð1Þ
Bioaccumulation factor ¼
Amount of fluoride in roots and leaves ðmgÞ Amount of fluoride in the medium ðmgÞ
ð2Þ
Estimation of total chlorophyll, carbohydrates, and proteins after fluoride removal The total chlorophylls in the cell-free extracts of leaves were measured using Arnon’s method (Arnon 1949). The carbohydrate concentrations were estimated using anthrone method (Roe, 1966). The total protein contents were estimated using Bradford’s method (Bradford 1976).
The plants were thought to undergo oxidative stress after fluoride (10 mg L−1) exposure, and therefore, the following marker enzymes such as SOD, CAT, and GPX were assayed. The assays were performed as per the manufacturer’s protocol. All the experiments were performed in triplicates and the data was analyzed with the Tukey-Kramer multiple comparison test.
Results and discussion Screening of plant species for fluoride removal from solution Among the tested plants, N. oleander, P. crinitum, P. oleracea, A. macrorrhizos, C. thevetia, T. angustifolia, B. oleracea, S. polyrhiza, C. bipinnatus, and L. inermis showed fluoride (5 mg L−1) removal up to 98, 84, 78, 73, 66, 67, 61, 59, 55, and 51%, respectively, over a period of 8 days. Further experiments with higher concentrations were carried out with P. oleracea, P. crinitum, and N. oleander. Single plant of P. oleracea, P. crinitum, and N. oleander when independently exposed to 200 mL NaF solution at a concentration of 10 mg L−1 revealed 73, 80, and 92% fluoride removal, respectively, within 15 days (Fig. 1). N. oleander was found to be superior to other plants. Saccharum officinarum, Camellia japonica, and Pittosporum tobira were shown to remove fluorides up to 40, 7.5, and 15%, respectively, from the solutions at a concentration of 4 mg L−1 within 21 days in earlier works (Santos-Díaz and Zamora-Pedraza 2010). Hydrilla verticillata could also remove 24.4% of the fluoride from solution at a concentration of 2.5 mg L−1 within 7 days (Sinha et al. 2000).
10 Concentration of Fluoride (mg L-1)
Fig. 1 Removal of fluoride by P. oleracea, P. crinitum, and N. oleander from the solution in 15 days
Analysis of abiotic stress marker enzymes after fluoride removal by N. oleander, P. crinitum, and P. oleracea
P. oleracea P. crinitum N. oleander
8 6 4 2
Days
Environ Sci Pollut Res Fig. 2 Effect of concentration of fluoride on uptake by N. oleander plants within 10 days
90
% Fluoride removal
80 70 60
10 mg L-1 20 mg L-1 30 mg L-1 40 mg L-1 50 mg L-1
50 40 30 20 10 0 Days
Effect of fluoride concentration and N. oleander plant biomass on removal
was also found to reduce from 64 to 20% when concentration was increased from 5 to 25 mg L−1 (Mohan et al. 2007).
With an increase in the fluoride concentration (10– 50 mg L−1), when monitored up to 15 days, N. oleander was found to remove 92, 81, 71, 60, and 51% fluoride, respectively (Fig. 2). Higher concentration was considered to be having inhibitory effects on the removal process. With the increase in the number of plants, i.e., 1, 2, 3, 4, and 5, when monitored up to 10 days, N. oleander removed 74, 79, 84, 90, and 98% fluoride, respectively (Fig. 3). The higher pollutant concentrations have earlier been shown to reduce the removal process whereas the increase in plant biomass favors the process (Khandare and Govindwar 2015). The fluoride uptake capacity of H. verticillata was also observed to be reduced by 40% when fluoride concentration was increased from 2.5 to 25 mg L−1 during a 10-day exposure in a hydroponic solution (Sinha et al. 2000). The efficiency of fluoride removal by Spirogyra
Accumulation of fluoride in plant tissues after a 15-day exposure The fluoride levels in root and leaf tissues tested after a 15-day exposure of 200 mL fluoride solution at 10 mg L−1 concentration revealed their different phytoremediation potentials calculated in terms of the translocation and bioaccumulation factors. N. oleander showed the highest translocation and bioaccumulation factors which is a characteristic of an ideal phytoremediator. P. oleracea and P. crinitum also followed the trait after N. oleander. After 15 days, the roots of N. oleander, P. crinitum, and P. oleracea showed 0.13, 0.16, and 0.14 mg of fluoride, respectively, whereas the leaves showed 0.24, 0.19, and 0.20 mg of fluoride in per gram of the fresh tissues, respectively. Thus, the translocation factors
100
Fig. 3 Effect of N. oleander plant biomass on fluoride uptake within 15 days
90
1 Plant
2 Plants
3 Plants
4 Plants
% Fluoride removal
80 70 60 50 40 30 20 10 0 Days
5 Plants
Environ Sci Pollut Res Table 1 Plant
Accumulation of fluoride in leave and root (mg g−1) fresh plant tissues after 15 days exposure Samples Fluoride in leaves A
Fluoride in roots B
Accumulated fluoride Remaining fluoride in (mg) solution (mg) Ca D
Translocation factor A/B
Bioaccumulation factor C/D
N. oleander Control
0.17 ± 0.04
0.10 ± 0.03
2.7 ± 0.16
NA
1.70
NA
Test Control
0.24 ± 0.09 0.18 ± 0.06
0.13 ± 0.08 0.14 ± 0.06
3.7 ± 0.23 2.5 ± 0.22
0.38 ± 0.07 NA
1.85 1.28
9.8 NA
P. crinitum
Test P. oleracea Control Test
0.19 ± 0.04
0.16 ± 0.05
2.8 ± 0.20
0.77 ± 0.11
1.19
3.6
0.15 ± 0.08 0.20 ± 0.07
0.12 ± 0.06 0.14 ± 0.04
1.9 ± 0.31 2.4 ± 0.34
NA 1.08 ± 0.18
1.25 1.43
NA 2.2
NA not calculated as initial values were not available (A + B) × total weight of the leaves and roots in grams (given in the BDetection of fluoride in leaves and stem and subsequent analysis^ section)
Effect of fluoride uptake on chlorophyll, carbohydrate, and protein contents in plants The fluoride accumulation is known to reduce the chlorophyll content of the leaves, thereby ultimately decreasing the carbohydrate synthesis. The chlorophyll levels in P. oleracea, P. crinitum, and N. oleander were also found to be reduced from 26.8, 24.6, and 30.2 to 16.2, 10.6, and 28.3 μg mL−1, respectively, after 15 days of fluoride exposure. The leaves of H. perforatum and C. sinensis tested for fluoride removal were also shown to reduce chlorophyll levels in the leaves (Fornasiero 2003; Li et al. 2011. In another study, a 28-day exposure to fluoride at a concentration of 2.5–10 mg L−1 decreased the chlorophyll contents up to 40–60% signifying that such prolonged contact to this anion can directly affect the photosynthesis (Camarena-Rangel et al. 2015). Reduction in the chlorophyll content in the leaves of Pisum sativum, Oryza sativa, and Triticum aestivum was also observed up to more than 25% (Sabal et al. 2006; Gupta et al. 2009; Bhargava and Bhardwaj 2010). The almond and apricot tree leaves were observed to show necrosis after fluoride accumulation of
110 and 65 μg g−1 dry weights, respectively (Mezghani et al. 2005). The decrease in chlorophyll ultimately reduced the carbohydrate content in plant tissues. Fluorides are considered as influential enzymatic inhibitors which ultimately affect the physiological processes such as carbohydrate metabolism (Miller 1993). The carbohydrate levels in P. oleracea, P. crinitum, and N. oleander leaves were reduced by 50, 44, and 16%, respectively, after 15 days exposure (Fig. 4). The fluoride accumulation was thought to reduce the conversion of sugars to carbohydrates (Asthir and Singh, 1995). Sugar and starch contents in the leaves of Amygdalis communis was also found to be reduced by 75 and 85%, respectively, after 10 mM fluoride solution exposure (Elloumi et al. 2005). Similarly, 10 mg L−1 NaF solution exposure to paddy seedlings was found to show around 30% reduction in sugar contents after 15 days (Gupta et al. 2009). The total protein levels in the leaves of P. oleracea, P. crinitum, and N. oleander were observed to be reduced by 38, 53, and 15% (Fig. 4). Protein levels were not altered significantly in N. oleander leaves after 15 days of exposure. However, the decrease in protein concentration in
0.48 110 0.43 90 0.38 70 0.33 50
30
10
P. oleracea Carbohydrates P. crinitum Carbohydrates N. oleander Carbohydrates P. oleracea Proteins P. crinitum Proteins N. oleander Proteins
0.28
Proteins (µg mL -1)
for N. oleander, P. crinitum, and P. oleracea were observed to be 1.85, 1.19, and 1.43, respectively. After calculating the total fluoride in roots and leaves together and comparing it with the remaining fluoride in solution, the bioaccumulation factors of 9.8, 3.6, and 2.2 were noted for N. oleander, P. crinitum, and P. oleracea, respectively. The values of the amount of fluoride accumulated in plant tissues before experiments have also been given as controls (Table 1). These particular attributes are properties of efficient phytoremediators. The translocation factor of greater than 1 is a characteristic property for an ideal phytoremediation candidate plant (Gupta and Banerjee 2009). The plants of Hypericum perforatum were also found to accumulate fluoride in the leaves (Fornasiero 2001). The roots of Allium cepa and Prosopis juliflora conversely showed more accumulation of fluoride in roots than in shoots (Jha et al. 2009; Saini et al. 2012).
Carbohydrates (µg mL -1)
a
0.23 0.18
Days
Fig. 4 Effect of fluoride accumulation on protein and carbohydrate contents in the plant leaves
Environ Sci Pollut Res Table 2
Enzyme analysis of plant tissues on 0 days and after 15 days of 10 mg L−1 fluoride solution exposure P. oleracea
Enzymes
P. crinitum Control
N. oleander
Control
Test
Test
Control
Test
0.40 ± 0.007 0.01 ± 0.002 0.04 ± 0.007
1.93 ± 0.07* 0.05 ± 0.06** 0.24 ± 0.01*
0.94 ± 0.13 0.03 ± 0.01 0.05 ± 0.03
1.924 ± 0.19* 0.054 ± 0.01* 0.262 ± 0.03*
1.62 ± 0.24 0.72 ± 0.08 0.21 ± 0.03
2.86 ± 0.30** 1.82 ± 0.03* 0.36 ± 0.05*
0.013 ± 0.001 0.010 ± 0.003 0.242 ± 0.002
0.045 ± 0.008* 0.065 ± 0.008* 0.642 ± 0.062*
0.022 ± 0.005 0.025 ± 0.009 0.032 ± 0.002
0.072 ± 0.008* 0.074 ± 0.008* 0.110 ± 0.009*
0.012 ± 0.003 0.005 ± 0.001 0.180 ± 0.011
0.041 ± 0.005** 0.019 ± 0.006** 0.512 ± 0.124*
Root tissues Catalasea Superoxide dismutaseb Glutathione peroxidasec Leaf tissues Catalasea Superoxide dismutaseb Glutathione peroxidasec
Values are a mean of three experiments ± SD. Significantly different from respective control (0 h) at *P < 0.05, **P < 0.01, and ***P < 0.001 by one-way ANOVA with Tukey-Kramer comparison test NA no activity a
50% inhibition of the NBT photoreduction rate (U mg−1 protein)
b
Nanomoles of H2O2 utilized (U mg−1 protein)
c
Activity in units min−1 mg−1
P. crinitum and P. oleracea was noted as in Salicornia brachiata (Reddy and Kaur 2008) after sodium fluoride exposure. Exposure of fluorides at 15–25 mg L − 1 to H. verticillata roots was found to show reductions in protein contents of the leaves by 25–30% (Sinha et al., 2000). A fluoride concentration of 50 mg L − 1 exposed to Abelmoschus esculentus seedlings also exerted negative effect on protein content reducing it by 50% (Iram and Khan 2016).
hydroponically grown C. sinensis seedlings when kept in contact with 0.11 and 0.21 mM fluoride solution were reported to reveal significant enhancement in CAT and GPX activities (Li et al. 2011). Activities of CAT and peroxidase were found to be elevated by 3.2- and 2.7-folds, respectively, in P. juliflora after fluoride exposure (Saini et al. 2013). Similarly, activity of SOD was in the seeds of O. sativa was increased by 75% (Chakrabarti and Patra 2015).
Analysis of oxidative stress marker enzymes
Conclusions
The oxidative stress is an inevitable phenomenon after plant exposure to abiotic stress of various types. The root and leaf samples of the tested plants before and after fluoride removal from the solution were assayed for marker enzymes of the oxidative stress. The activities of SOD, CAT, and GPX in the roots of P. oleracea were observed to be induced by 400, 383, and 500%, respectively. P. crinitum root also revealed 80, 105, and 424% respective inductions in the activities. N. oleander roots on the other hand showed lowered expression in the activities of SOD, CAT, and GPX with inductions of 153, 77, and 71%, respectively. The leaves of P. oleracea and P. crinitum showed induction in the activities of SOD, CAT, and GPX by 550, 315, and 165%, and 196, 227, and 243%, respectively. N. oleander leaves however revealed SOD, CAT, and GPX activities to be induced by 280, 242, and 184%, respectively. These increased expressions might have occurred due to superior translocation of fluoride exhibited by N. oleander (Table 2). In earlier studies, SOD and CAT activities in C. sinensis and mulberry cultivars were also found to show significantly alleviated levels upon exposure to fluoride (Kumar et al. 2009; Li et al. 2011). The
Among the tested plants, P. oleracea, P. crinitum, and N. oleander showed noteworthy removal of fluoride from solution. N. oleander was observed to be superior among these plants. It also showed better translocation and bioaccumulation factors which are key characteristics for an ideal phytoremediator. The plants’ chlorophyll, carbohydrate, and protein contents were observed to be decreased after fluoride removal. N. oleander however remained least affected. Use of fluoride hyper-accumulator plants which could withstand high fluoride concentrations would be a benign, simple, and lowcost approach for removal of these pollutants from soils and water. Acknowledgements Rahul V. Khandare is thankful to the Science and Engineering Research Board, New Delhi, India, for providing the research funds (Grant No. SERB/LS-54/2014). Anuprita D. Watharkar would like to thank the University Grants Commission (UGC), New Delhi, India, for providing post-doctoral fellowship. Shivtej P. Biradar and Pankaj K. Pawar are thankful to UGC for funding under Special Assistance Program (SAP-DRS II, Grant No. F.4-8/2015/DRS II (SAP II)) to the Department of Biochemistry, Shivaji University, Kolhapur, India.
Environ Sci Pollut Res
References APHA (1998) Standard methods for the examination of water and wastewater, 20th ed. American Public Health Association, Washington, DC Amor Z, Malki S, Taky M, Bariou B, Mameri N, Elmidaoui A (1998) Optimization of fluoride removal from brackish water by electrodialysis. Desalination 120:263–271 Arnon D (1949) Copper enzyme polyphenoloxides in isolated chloroplast in Beta vulgaris. Plant Physiol 24:1–15 Asthir B, Singh R (1995) Fluoride-induced changes in the activities of sucrose metabolizing enzymes in relation to starch accumulation sorghum caryopsis, raised through liquid culture. Plant Physiol Biochem 33:219–223 Bassin E, Wypij D, Davis R, Mittlema M (2006) Age-specific fluoride exposure in drinking water and osteosarcoma (United States). Cancer Causes Control 17:421–428 Bhargava D, Bhardwaj N (2010) Effect of sodium fluoride on seed germination and seedling growth of Triticum aestivum VAR. RAJ. 4083. J Phytol 2:41–43 Bradford M (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Analytic Biochem 72:248–254 Chakrabarti S, Patra P (2015) Biochemical and antioxidant responses of paddy (Oryza sativa L.) to fluoride stress. Fluoride 48:56–61 Camarena-Rangel N, Velázquez A, Santos-Díaz M (2015) Fluoride bioaccumulation by hydroponic cultures of camellia (Camellia japonica spp.) and sugar cane (Saccharum officinarum spp.). chemosphere 136:56–62 Cooke J, Andrewa S, Johnson M (1990) The accumulation of lead, zinc, cadmium and fluoride in the wood mouse. Water Air Soil Pollut 51: 56–63 Duraiswami R, Patankar U (2011) Occurrence of fluoride in the drinking water sources from Gad river basin, Maharashtra. J Geol Soc India 77:167–174 Elloumi N, Abdallah F, Mezghani I, Rhouma A, Boukhris M (2005) Effect of fluoride on almond seedlings in culture solution. Fluoride 38:193–198 Fornasiero R (2001) Phytotoxic effects of fluorides. Plant Sci 161:979– 985 Fornasiero R (2003) Fluorides effects on Hypericum perforatum plants: first field observations. Plant Sci 165:507–513 Gupta S, Banerjee S (2009) Fluoride accumulation in paddy (Oriza sativa) irrigated with fluoride contaminated groundwater in an endemic area of the Birbhum District, West Bengal. Fluoride 42:224– 227 Gupta S, Banerjee S, Mondal S (2009) Phytotoxicity of fluoride in the germination of paddy (Oryza sativa) and its effect on the physiology and biochemistry of germinated seedlings. Fluoride 42:142–146 Iram A, Khan T (2016) Effect of sodium fluoride on seed germination, seedling growth and biochemistry of Abelmoschus esculentus. J Plant Biochem Physiol 4:170 Jagtap S, Yenkie M, Labhsetwar N, Rayalu S (2012) Fluoride in drinking water and defluoridation of water. Chem Rev 112:2454–2466 Jha S, Nayak A, Sharma Y (2009) Fluoride toxicity effects in onion (Allium cepa L) grown in contaminated soils. Chemosphere 76: 353–356 Kang D, Tsao D, Wang-Cahill F, Rock S, Schwab A, Banks M (2008) Assessment of landfill leachate volume and concentration of cyanide and fluoride during phytoremediation. Bioremediation J 12:32–45
Khandare R, Govindwar S (2015) Phytoremediation of textile dyes and effluents: Current scenario and future prospects. Biotechnol Adv 33: 1697–1714 Kumar N (2011) Variation of fluoride and correlation with alkalinity in groundwater of shallow and deep aquifers. Int J Environ Sci 5:884– 890 Kumar K, Varaprasad P, Rao A (2009) Effect of fluoride on catalase, guiacol peroxidase and ascorbate oxidase activities in two verities of mulberry leaves (Morus alba L.). Res J Earth Sci 1:69–73 Li C, Zheng Y, Zhou J, Xu J, Ni D (2011) Changes of leaf antioxidant system, photosynthesis and ultrastructure in tea plant under the stress of fluorine. Biol Plant 55:563–566 Mameri N, Yeddou A, Lounici H, Belhocine D, Grib H, Bariou B (1998) Defluoridation of septentrional sahara water of North Africa by electrocoagulation process using bipolar aluminium electrodes. Water Res 32:1604–1612 Mezghani I, Elloumi N, Abdallah F, Chaieb M, Boukhris M (2005) Fluoride accumulation by vegetation in the vicinity of a phosphate fertilizer plant in Tunisia. Fluoride 38:69–75 Miller G (1993) The effect of fluoride on higher plants: with special emphasis on early physiological and biochemical disorders. Fluoride 26:3–22 Mohan S, Ramanaiah S, Rajkumar B, Sarma P (2007) Biosorption of fluoride from aqueous phase onto algal Spirogyra IO1 and evaluation of adsorption kinetics. Bioresour Technol 98:1006–1011 Paudyal H, Pangeni B, Inoue K, Kawakita H, Ohto K, Ghimire K, Alam A (2013) Preparation of novel alginate based anion exchanger from Ulva japonica and its application for the removal of trace concentrations of fluoride from water. Bioresour Technol 148:221–227 Reddy M, Kaur M (2008) Sodium fluoride induced growth and metabolic changes in Salicornia brachiata Roxb. Water Air Soil Pollut 188: 171–179 Roe J, Dailey R (1966) Determination of glycogen with the anthrone reagent. Analytic Chem 15:245–250 Ruan J, Ma L, Shi Y, Han W (2003) Uptake of fluoride by tea plants (Camelia sinensis L.) and the impact of aluminium. J Sci Food Agric 83:1342–1348 Sabal D, Agrawal D, Khan K (2006) Effect of fluoride on physiological parameters of Pisum sativum, var. Azad P-1. Int J Biosci Reporter 4: 15–18 Saini P, Khan S, Baunthiyal M, Sharma V (2012) Organ-wise accumulation of fluoride in Prosopis juliflora and its potential for phytoremediation of fluoride contaminated soil. Chemosphere 89: 633–635 Saini P, Khan S, Baunthiyal M, Sharma V (2013) Effects of fluoride on germination, early growth and antioxidant enzyme activities of legume plant species Prosopis juliflora. J Environ Biol 34:205–209 Santos-Díaz M, Zamora-Pedraza C (2010) Fluoride removal from water by plant species that are tolerant and highly tolerant to hydrogen fluoride. Fluoride 43:150–156 Sinha S, Saxena R, Singh S (2000) Fluoride removal from water by Hydrilla verticillata (l.f.) Royle and its toxic effects. Bull Environ Contam Toxicol 65:683–690 Sivasamy A, Singh K, Mohan D, Maruthamuthu A (2001) Studies on defluoridation of water by coal-based sorbents. J Chem Technol Biotechnol 76:717–722 Zhou J, Gao J, Liu Y, Ba K, Chen S, Zhang R (2012) Removal of fluoride from water by five submerged plants. Bull Environ Contam Toxicol 89:395–399
