Short CommunicationOrgan-wise accumulation of fluoride in Prosopis juliflora and its potential for phytoremediation of fluoride contaminated soil
Highlights
► Fluoride contamination is a global environmental problem. ► Fluoride rich soil is a potential source of contamination of water and vegetation. ► Bioaccumulation and translocation factor being >1.0 showed tolerance of plant to F. ► Prosopis juliflora plant acts as a remarkable phytoremediator.
Introduction
The global environmental problem concerning the ecological contamination is one of the most serious problems facing the world today. Heavy metals and non-metals (F) contaminated soils pose an increasing problem to human, animal and plant health. While F is necessary for normal growth of plants in lesser amounts (Pilon-Smits et al., 2009), at high concentration it has considerable potential for causing ecological damage owing to its non-biodegradable nature and slow accumulation in the environment.
Various defluoridation techniques, namely Nalgonda (based on addition of lime and alum) and Prasanthi (based on adsorption using activated alumina) have been practiced in past (Bulusu and Nawlakhe, 1990). However, these techniques are not effective, as they remove only a small portion of F. The conventional remediation technologies (other than bioremediation) used for in situ and ex situ remediation are typically expensive and destructive (Mandakini et al., 2005). Therefore, it is important to develop economically viable and effective method to decontaminate soils from F contamination.
The prospect of using plants in the reclamation of soils contaminated with heavy metals (Chaney et al., 1997) and non-metals (Baunthiyal, 2008) have gained considerable importance in recent years. This approach essentially involves using plants that accumulate specific metals and nonmetal in them. Phytoremediation refers to a diverse collection of plant-based technologies that use either naturally occurring or genetically engineered plants for cleaning contaminated environments (Cunningham et al., 1995). Phytoremediation, a sound environmental technology (Al-Qurainy and Abdel-Megeed, 2009), can be of great potential in removal of F from water and contaminated soil.
Prosopis juliflora is a leguminous, perennial phreatophyte tree, widely distributed in arid and semi-arid regions of world. It also naturally grows in F endemic areas of Rajasthan (India) without showing any morphological distortions. It is tolerant to very high temperatures (viz. 48 °C). The roots penetrate to great depths in the soil and can grow in wide range of soils such as saline, alkaline, sandy and rocky soils (George et al., 2007). The genus is widely distributed in the dry tropical and sub-tropical regions of Central and Northern South America, Africa and Asia, particularly in India. It has been proved to be the only exotic species capable of growing in a wide variety of soils and climate conditions. P. juliflora is known to be tolerant to heavy metals, e.g. cadmium, chromium, and copper (Kumar et al., 2005).
All these advantages of P. juliflora prompted us to assess the potential use of this plant in the reclamation of F contaminated soils. Hence the present study was undertaken to investigate the effects of F on growth parameters, organ-wise accumulation, translocation and bioaccumulation factors using P. juliflora in order to test its potential use in phytoremediation of F contaminated soils.
Section snippets
Experimental design
Seeds of P. juliflora L. were obtained from Central Arid Zone Research Institute (CAZRI) Jodhpur (Rajasthan) India. The seeds were surface sterilized, imbibed and sown in plastic pots containing soilrite. 250 g soilrite was poured in each pot and thoroughly mixed with a corresponding amount of sodium fluoride (NaF) to give an end concentration of 25, 50, 75, 100 mg NaF kg−1 soilrite. For each treatment of F, three independent sets of plants were maintained. Pots without NaF served as a control. The
Effect of fluoride on plant growth
The effects of various F concentrations on shoot and root length in P. juliflora seedlings are shown in terms of growth ratio (GR). The GR of P. juliflora was evaluated at 5 concentrations of F (control, 25, 50, 75, 100 mg NaF kg−1 soilrite). The results show that in general, both GR and TI values show significant inverse correlation (P ⩽ 0.05) with F concentration (Table 1). Thus the TI values gradually decline from 1.0 in untreated plants to 0.64 as 100 mg NaF kg−1 soilrite. There is a steady decline
Acknowledgements
Authors are deeply grateful to Prof Aditya Shastri for providing research facilities under the Basic Science Project of DST, New Delhi. The authors are also thankful to Bioinformatics Centre, Banasthali University, India for extensive use of computational facilities.
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These authors contributed equally.