Effects Of The Iron Manganese Oxidizing Bacteria On Iron Plaque Formation And Cd Uptake And Translocation In Rice

Iron and manganese oxidizing bacteria is one of the important biological factors to promote the circulation of Fe and Mn elements in crust. Iron plaque is one of the important mechanisms for aquatic plants to adapt to flooding and other environmental stresses. For the whole growth period of rice was under flooded condition, Iron, manganese element in different valence state transformation were promoted by means of the physiological activities of iron and manganese oxidizing bacteria. The activity of iron and manganese elements in rhizosphere soil were changed and the formation of iron film on rice root surface was influenced. In this paper, greenhouse hydroponic experiments and pot experiments were carried out to study the influence of the formation of iron film and heavy metal uptake and transport in rice by Iron and Manganese Oxidizing Bacteria. The main results were summarized as follows:1. D416 （Burkholderia sp.）and YGL（Pseudomonas sp.） were able to increase the rhizosphere redox potential and to promote the formation of iron manganese oxide film in the rhizosphere of rice.2. Oxygen permeability ability was promoted during the two major growth periods （tillering and jointing booting stage） with adding iron and Manganese Oxidizing Bacteria in the experiments of hydroponic rice. And the formation of root iron plaque was also promoted. The rate of oxygen permeability ability was increased mostly with the processing of B （YGL alone） and AB （D416 and YGL mixed） during the tillering stage of rice.3. ROS （Reactive oxygen species） was increased gradually with prolonging growth period of rice in hydroponic culture. And the increasing of the ROS content was inhibited with the adding of iron and manganese oxidizing bacteria. But SOD （Superoxide dismutase）, GST （Glutathione S-transferase）, and the enzyme activity of APX （Ascorbate peroxidase）were decreased or were changed insignificant. Rice pot add iron and Manganese Oxidizing Bacteria to protect the plants from ROS toxicity, which AB treated SOD, APX, GST enzyme activity significantly reduce, adding iron and Manganese Oxidizing Bacteria avoid enzyme overexpression, improve plant of adverse environmental resistance and soil culture of rice on the enzyme had the best effect for AB.4. The contents increase of Fe and Mn content in the iron plaque were promoted with the adding of Iron and Manganese Oxidizing Bacteria in the experiments of Hydroponic rice. And The transfer of Fe and Mn to the roots in iron plaque was inhibited during seedling stage and tillering stage in this exprimentd. But the transfer of Fe and Mn elements to the roots in iron plaque was promoted during the jointing booting stage. Soil cultivated rice of adding iron and Manganese Oxidizing Bacteria inhibited the translocation of Fe elements in the main components of the iron plaque to the upper and the grain, and promoted the translocation of Mn elements of the iron plaque to the upper and the grain, promoted the photosynthetic rate, and increased the biomass of rice. The treatment effect is best for the AB treatment.5. The accumulation of Cd elements to iron plaque was promoted with the adding of iron and manganese oxidizing bacteria, and the translocation of Cd into rice plants was inhibited. Hydroponic rice seedling roots accumulated more Cd content,The tillering stage Cd accumulated more Cd in shoots,but in rice jointing booting stage shoot Cd accumulation decreased, more Cd accumulated in the roots. Soil culture rice B treatment, promoted the accumulation of Cd into roots and husk, inhibited the Cd translocation to shoots and brown rice. Cd content in brown rice is lower than the national food hygiene standard of 0.2 mg.Kg^-1,the paper provides new ideas for the heavy metal Cd pollution of farmland rice Cd exceeded governance.