Ultrastructure and subcellular distribution of Cr in Iris pseudacorus L. using TEM and X-ray microanalysis
- 413 Downloads
Chromium pollution of freshwater is hazardous for humans and other organisms, and places a limitation on the use of polluted water sources. Phytoremediation, the use of plants to remove pollutants from the environment, is a cost-effective, environmentally friendly approach for water decontamination. To improve the efficiency of the process, it is essential to increase the current knowledge about Cr accumulation in macrophytes. Plants of Iris pseudacorus L. were treated with Cr(III) at 0.75 mM for 5 weeks to investigate Cr localization by means of transmission electron microscopy and energy dispersive X-ray analysis. Chromium induced severe ultrastructural alterations in the rhizodermis (cell wall disorganisation, thickening, plasmolysis, and electron-dense inclusions) and rhizome parenchyma (reduced cell size, cell wall detachment, vacuolation, and opaque granules). The highest Cr contents were found in the cell walls of the cortex in the roots and in the cytoplasm and intercellular spaces of the rhizome. The Cr concentration in root tissues was in the order cortex >rhizodermis >stele, whereas in the rhizome, Cr was evenly distributed. It is proposed that root and rhizome have distinct functions in the response of I. pseudacorus to Cr. The rhizodermis limits Cr uptake by means of Si deposition and cell wall thickening. The rhizome cortex generates vacuoles and granules where Cr co-occurs with S, indicating Cr sequestration by metal-binding proteins.
KeywordsChromium Metal Rhizome Subcellular localization Ultrastructure X-ray microanalysis
Energy dispersive X-ray analysis
Transmission electron microscopy
United States Environmental Protection Agency
This study was part of the International Cooperation European Project MEDINDUS, EC contract no INCO-CT-2004-509159. TEM and LM images were obtained in the TEM Laboratory of the University of Barcelona. X-ray microanalysis was performed in the Microscopy Service of the Autonomous University of Barcelona.
- Bringezu K, Lichtenberger O, Leopold I, Neumann D. Heavy metal tolerance of Silene vulgaris. J Plant Physiol. 1999;154:536–46.Google Scholar
- Peralta JR, Gardea-Torresdey JL, Tiemann KJ, Gómez E, Arteaga S, Rascon E, et al. Uptake and effects of five heavy metals on seed germination and plant growth in alfalfa (Medicago sativa L). Bull Environ Cont Toxicol. 2001;66:727–34.Google Scholar
- Qiu S, Huang S. Study on growth and Cd accumulation of root system of Iris pseudacorus seedling under Cd stress. J Plant Res Environ. 2008;17:33–8.Google Scholar
- Vajpayee P, Rai UN, Ali MB, Tripathi RD, Yadav V, Sinha S, et al. Chromium-induced physiologic changes in Vallisneria spiralis L. and its role in phytoremediation of tannery effluent. Bull Environ Cont Toxicol. 2001;67:246–56.Google Scholar