Studied On The Potential Of Vetiveria Zizanioides For Phytoremediation

Cadmium in the soil is stable, accumulative, and hard to be removed. Through food chain,it may do harm to people by resulting in chronic diseases. In Chinese vast countryside,the soil pollution by cadmium is serious. Phytoremediation technology is the best soil cadmium pollution control technology, and the research in recent years become a hot spot. The physiological and ecological effects ,including activities of root dehydrogenase, nitrate reductase(NR), three kinds of antioxidant enzymes (CAT,POD,SOD), contents of chlorophyll, ascorbic acid and cell membrane permeability, Vetiveria zizanioides(V.zizanioides) grown in hydroponic culture under the stresses at different concentration of Cadmium(Cd) and combined pollution with lead(Pb) were studied. The main results are as follows:1. The experimental results show that Cd mainly cumulated in root. The highest Bioconentration factor(BF) is 24.06% .The treatment concentration had a appositive correlation with Cd accumulation in root (r=0.9874), while it has negative correlation with tolerance index of root(r=-0.94362). Bioconentration factor decreasing when accumulation was increasing. That shows the cumulated of Cd has a saturated upper limit;2. The V.zizanioides root elongation has negative correlation with treatment concentration; the tolerance index was 40.20% at 2.5 mmol?L-1Cd, The root activity and nitrate reductase(NR)activity appeared an increase and then a decrease trend in low concentration treatment of Cd (≤1mmol?L-1)with time. At latter time the root exhibits a adaptability ;the root activity and nitrate reductase activity appeared an obvious descending trend in middle and high concentration treatment of Cd (≥1.5mmol?L-1), and descending extent increased with concentration of Cd increase. CAT, POD, SOD appeared an increase first and then a decreased trend in low concentration treatment of Cd and lower with time. V.zizanioides normal growth critical concentration was 0.5mmol?L-1;3. Sequential extraction revealed that NaCl extractable-Cd was dominant in both roots and leaves of V.zizanioides. The average proportion is 52.06 and 64.03. V.zizanioides nitrogen metabolism ,respiration and growth development inhibited by Cd stress, it still has strong tolerance level and accumulation ability;4. At Cd, Pb combined pollution treatments, chlorophyll contents, ascorbic acid contents, root dehydrogenase and NR respectively decreased to 76.25%,45.44%,51.23% and 48.87% of control group, cell membrane permeability increased to 1.29 times control. Pb had less impact on these parameters. But combined pollution had a greater effect than single pollution;This study show that V.zizanioides had a great tolerance to Cd, its root accumulation ability was strong ,the ratio of Cd moving to above ground parts was little. These characteristics make V.zizanioides had great potentialities in rhizosphere technology,heavy metal pollution control ,soil and water conservation at farmland ,vegetation restoration at mining area.