Physiological strategies of Eichhornia crassipes (Mart.) Solms to tolerate Cr6+ accumulation, compared to a sensitive species Pistia stratiotes L.

Chromium in the form of hexavalent chromium (VI) has been used in some industry including leather tanning industry. The chemical has been known to be harmful to living organisms. Therefore, it is important to treat wastewater from leather tanning industry before being discharged to the environment. The aim of this study is to examine ecophysiological strategies of waterhyacinth (Eichhornia crassipes) to tolerate Cr6+ accumulation in its tissue, compared to sensitive species water lettuce (Pistia stratiotes). The plants were cultivated in containers containing Hoagland medium and treated with some variation of Cr6+ concentrations of Cr6 i.e. 0, 40, 80 and 120 ppm for 14 days. Some parameters including CAT (catalase), Ascorbate peroxidase (APX), chlorophyll concentration and proline in the plants were measured. The biomass yield of plant in Cr6+ stress was negative (-0.732 to -1.84 g/week) which indicated both E. crassipes and P. stratiotes reduced their growth. The higher the concentration of Cr6+, the lower the chlorophyll contents in the leaves. The lowest of chlorophyll content was in 120 ppm (0.15 mg/g in P. stratiotes and 0.12 mg/g in E. crassipes). The highest of CAT activity in E. crassipes was 109% in 40 ppm Cr6+, while in P. stratiotes was 76% in 120 ppm. Proline content in both E. crassipes and P. stratiotes were not different significantly. In general, E. crassipes plants have the ability to adapt to Cr6+ stress better compared to P. stratiotes which was severely damaged when grown in high Cr6+ concentration. Both plants can remediate waste fairly well (level of elimination 62-68%) during the exposure period of 14 days to Cr6+ solution