Effects of Chromium Species on Root Morphometry of Typha domingensis in Floating Treatment Wetlands

The aims were to evaluate the tolerance of Typha domingensis and the changes in the internal morphometric parameters of roots exposed to different Cr(III) and Cr(VI) concentrations in Floating Treatment Wetlands (FTWs). FTWs were exposed to 5 and 10 mg L^- 1 Cr(III), and 5 and 10 mg L^- 1 Cr(VI). Also, a Biological Control (BC) without Cr addition was used. Roots were the main Cr accumulator organ. Both Cr species significantly modified the root morphology of T. domingensis. The highest cross-sectional areas (CSA) of roots, and metaxilematic vessels were observed in 5 and 10 mg L^- 1 Cr(III) treatments. The lowest CSA and number of vessels (NV) were observed in 5 and 10 mg L^- 1 Cr(VI) treatments. The lowest chlorophyll concentrations and growth rates were determined at 10 mg L^- 1 Cr(VI). Metaxylem vessels presented a disordered arrangement. Cr mapping from 10 mg L^- 1 Cr(VI) revealed a Cr deposit on the wall of the central cylinder and in the stele cells. Due to the morphological plasticity and tolerance demonstrated by T. domingensis, it can be concluded that it is a suitable species to be used in FTWs for the treatment of Cr-contaminated waters.