Biochemical and antioxidant responses of Ipomoea aquatica exposed to graded concentrations of chromium

The aquatic macrophyte Ipomoea aquatica Forssk. is widely distributed in many countries of Asia, Africa, North America, and Australia. It is found in the wild as well as cultivated and consumed as a vegetable in South and South East Asia. When I. aquatica was exposed to low concentrations (0.01-2 mg L- 1) of Cr (VI) for a 15 day period, it was observed that concentrations as low as 0.01 mg L- 1 could cause reductions in protein and carbohydrate content in leaf, upper and lower stem of the plant. Cr (VI) could also increase catalase activity in leaf and lower stem at 1-2 mg Cr (VI) L- 1, though the increments in the upper stem were not statistically significant. Induction of proline occurred in leaf and upper stem at 1-2 mg Cr (VI) L- 1. On the other hand, the induction of proline in lower stem occurred at 0.01 mg Cr (VI) L- 1 on 15 d. Thus, the study revealed that Cr (VI) could cause toxic effects on I. aquatica at relatively low and environmentally relevant concentrations, though the plant mitigated these effects through enhanced activities of anti-oxidant enzymes such as catalase and increased accumulation of the non-enzymatic anti-oxidant proline.