Citric acid enhances the phytoextraction of manganese and plant growth by alleviating the ultrastructural damages in Juncus effusus L

Chelate-assisted phytoextraction by high biomass producing plant species enhances the removal of heavy metals from polluted environments. In this regard, Juncus effusus a wetland plant has great potential. This study evaluated the effects of elevated levels of manganese (Mn) on the vegetative growth...

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Published in:	Journal of hazardous materials 2009-10, Vol.170 (2), p.1156-1163
Main Authors:	Najeeb, U., Xu, L., Ali, Shafaqat, Jilani, Ghulam, Gong, H.J., Shen, W.Q., Zhou, W.J.
Format:	Article
Language:	eng
Subjects:	Antioxidants - metabolism Antioxidative enzymes Applied sciences Biomass Chelating Agents - pharmacology Chemical engineering Chloroplast ultrastructure Chloroplasts - drug effects Chloroplasts - ultrastructure Citric acid Citric Acid - chemistry Citric Acid - pharmacology Continental surface waters EDTA Enzymes Exact sciences and technology Glutathione Reductase - chemistry Juncus effusus Lipid Peroxidation Malondialdehyde Manganese Manganese - chemistry Manganese - isolation & purification Metal accumulation Microscopy, Electron, Transmission Natural water pollution Peroxidase - chemistry Plant biometry Plant Development Plant Shoots - drug effects Plant Shoots - growth & development Plant Shoots - ultrastructure Plants (organisms) Plants - metabolism Plants - ultrastructure Pollution Reactors Stresses Superoxide Dismutase - chemistry Thylakoid disruption Uptakes Water treatment and pollution
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Summary:	Chelate-assisted phytoextraction by high biomass producing plant species enhances the removal of heavy metals from polluted environments. In this regard, Juncus effusus a wetland plant has great potential. This study evaluated the effects of elevated levels of manganese (Mn) on the vegetative growth, Mn uptake and antioxidant enzymes in J. effusus. We also studied the role of citric acid and EDTA on improving metal accumulation, plant growth and Mn toxicity stress alleviation. Three-week-old plantlets of J. effusus were subjected to various treatments in the hydroponics as: Mn (50, 100 and 500 μM) alone, Mn (500 μM) + citric acid (5 mM), and Mn (500 μM) + EDTA (5 mM). After 2 weeks of treatment, higher Mn concentrations significantly reduced the plant biomass and height. Both citric acid and EDTA restored the plant height as it was reduced at the highest Mn level. Only the citric acid (but not EDTA) was able to recover the plant biomass weight, which was also obvious from the microscopic visualization of mesophyll cells. There was a concentration dependent increase in Mn uptake in J. effusus plants, and relatively more deposition in roots compared to aerial parts. Although both EDTA and citric acid caused significant increase in Mn accumulation; however, the Mn translocation was enhanced markedly by EDTA. Elevated levels of Mn augmented the oxidative stress, which was evident from changes in the activities of antioxidative enzymes in plant shoots. Raised levels of lipid peroxidation and variable changes in the activities of antioxidant enzymes were recorded under Mn stress. Electron microscopic images revealed several modifications in the plants at cellular and sub-cellular level due to the oxidative damage induced by Mn. Changes in cell shape and size, chloroplast swelling, increased number of plastoglobuli and disruption of thylakoid were noticed . However, these plants showed a high degree of tolerance against Mn toxicity stress, and it removed substantial amounts of Mn from the media. The EDTA best enhanced the Mn uptake and translocation, while citric acid best recovered the plant growth.
ISSN:	0304-3894 1873-3336