The Response Of Root Structure And Rhizosphere Soil Chemistry Of Echinodorus Osiris Plant To Cadmium

The wetland plants, different from xerphytes, have unique heavy metal tolerance due to their flooding environment. Echinodorus Osiris plant was studied in order to investigate the response of root structure and rhizosphere soil chemistry of Echinodorus Osiris plant to cadmium. The hydroponic experiment was conducted to study the changes of root radial oxygen loss (ROL), porosity, Fe plaque under the treatment of Cd. Rhizbox experiment to compare the changes of soil pH, soil Eh, available P, available S, Cd speciation in rhizosphere and non-rhizospher of plant. By doing this, we aim to provides some supplement in wetland plants tolerance to heavy metals, and help better use Echinodorus Osiris plants in phytoremediation. The major results as follows:1. The root retention plays an important role in plant tolerance to Cd. After incubation21days in5mg L-1and15mg L-1Cd treatments, the content of Cd reached1626.70mg kg-1and1782.85mg kg-1in plant root,294.67mg kg-1and366.19mg kg-1in plant shoot, respectively.2. The ROL existed in Echinodorus Osiris root, which is14.08μmol O2/(plant·d) under the control treatment. The ROL decreased with the Cd treatment, which is10.06μmol O2/(plant·d) and7.05μmol O2/(plant-d) under the5mg L-1and15mg L-1Cd treatments, respectively.3. The content of root Fe plaque and Cd in root Fe plaque increased with the Cd treatments, which is10.23mg kg-1,25.47mg kg-1and33.64mg kg-1under the control,5mg L-1and15mg L-1Cd treatments, respectively. The content of Cd in root Fe plaque were not detected in control treatment, but, it reached24.28mg kg-1å'Œ41.84mg kg-1under the Cd treatments, respectively.4. There was a significant negative corerelation between the root Fe plaque and ROL, root porosity, which indicate that the increase of root Fe plaque resulted in the decrease of ROL and root porosity. The positive correlation between root Fe plaque and Fe plaque contained Cd showed that the exsit of Fe plaque was benefit for the plant uptake of Cd.5. The scanning electron microscopy with X-ray microanalysis photo indicates that the plant has high transport ability of Cd from root to above ground, however, the Casparian strips plays more important role in restrict of Cd transport into shoot.6. The higher plant Cd and biomass in flooded soils indicates that flooding benefits plant growth and tolerance to Cd. There is a37.89-53.04%and23.63-28.06%increase of shoot biomass and Cd, and a139.05-230.24%and23.81-21.99%increase of root biomass and Cd, respectively.There is a4.33%å'Œ4.03%increase of acid extractable Cd in flooded and non-flooded soil under15mg L-1Cd treatment while there is a1.48%å'Œ3.17%increase of that under30mg L-1Cd treatment. The plant root can activate the Cd in soil in certain Cd content.