Ultraestructural changes induced by chromium (VI) in water hyacinth (Eichhornia crassipes) leavesIn this study cellular alterations induced by Cr (VI) were determined on the water hyacinth, Eichhornia crassipes [Mart.]Solm-Laubach, through high resolution optical microscopy and transmission electron microscopy.Mature plants of E. crassipes were acclimated and exposed to 0, 10, 20 and 30 mg/l of chromium (VI) during 144 hours under controlled conditions in a greenhouse.Ultrastructural and tisular damages induced by chromium were determined comparing control (no metal) and Cr exposed plants.E. crassipes showed damages on the structure and distribution of thylakoid membranes by exposition higher to 20 mg/l.It was observed that plants exposed to 20 mg/l of Cr (VI) showed chloroplast membrane disruption and low stacking grana.It was not observed ultrastructure damages in E. crassipes chloroplasts in chromium concentrations below to 20 mg/l.It was observed a high Cr (VI) accumulation on water hyacinth root tissues exposed to 20 and 30 mg/l.