Chromium is one of the heavy metals used in industrial fields, i.e., metallurgical industry, chemical industry, heat-retardant, and leather tanning industry. Untreated wastewater from these industries can pollute rivers and threaten the aquatic ecosystem. Some aquatic plants such as water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) have been known as metal hyperaccumulators and can be used as phytoremediator for polluted water. This aim of the study is to determine the physiological and morphological responses of water hyacinth and water lettuce plants treated by different concentrations of trivalent chromium and to study which plant is effective for trivalent chromium removal. The experiment was conducted for 2 week at screen house. After two weeks, the plants were harvested and the weight was measured. The samples were separated into shoot and root and were analyzed for Cr content, chlorophyll, proline and CAT enzyme activity. The results of this study indicated that the levels of water hyacinth chromium in roots and leaves are lower (863.988 mg/Kg, 899.126 mg/Kg, 685.877 mg/Kg for treatment 40 ppm, 80 ppm, and 120 ppm respectively) than the levels of chromium in water lettuce (1584.264 mg/Kg, 1660 mg/Kg, 1413 mg/Kg for treatment 40 ppm, 80 ppm, and 120 ppm respectively). Physiological parameter, i.e., chlorophyll and proline levels in water hyacinth and water lettuce from all concentration treatment did not differ significantly (P> 0.05). The activity of the catalase enzyme in water hyacinth and water lettuce decreased with increasing chromium levels. The highest catalase enzyme activity was observed in control treatment of water lettuce (1.61 unit/mg) and 40 ppm treatment of water hyacinth (1.006 unit/mg). The highest biomass dry weight of both plants was found in plants with control treatment (15.38 gr and 8.48 gr for water hyacinth and water lettuce respectively). Therefore, we concluded that water lettuce is better for trivalent chromium removal than water hyacinth.

In leather tannery industry such as a case in Sukaregang, Garut, untreated or poorly treated wastewater which contain chromium has been severely polluting nearby river. The polluted river water (PRW) has been used by local farmers to irrigate their paddy fields. In this study we planted Sarinah variety (Svar) and Rojolele variety (Rvar) of paddy in soil and watered with PRW, K2Cr2O7 solutions with concentration of 50 and 100 mg/L and clean water as a control, for a period of four months. Chromium solutions were added gradually to the soil until reached final concentrations of 50 and 100 mg/L. The result showed that the treatment with PRW and Cr solutions reduced plants weight, shoot length and paddy production. Treatment with Cr solutions significantly decreased plants fresh and dry weight by 26.53% and 36.69% for Svar, 32.14% and 19.74% for Rvar. Paddy yield also decreased as higher Cr concentration was accumulated in plant tissues. The amount of filled grains decreased by 33.05%, while empty grains increased by 50.21% in Svar. In Rvar the amount of filled grains decreased by 21.44% and empty grains increased by 31.95%. Chromium treatment by gradual increase allowed plant to survive at an exposure of 100 ppm Cr, although the plant reduced its growth, biomass and yield.