| The decreased rice production and quality have directly affected by cadmium pollution,thus pose a threat to human health.How to prevent rice from cadmium pollution has aroused people's high attention.Pseudomonas aeruginosa,a strain isolated from the rhizosphere soil of rice,having high cadmium enrichment capacity was used as material in this study.Bacterial agents were prepared basing on the determination results of heavy metal pollution tolerance and crop growth inhibition of the strain,and further hydroponic experiment with added cadmium were conducted to disccuss the physiological and biochemical mechanism of rice relieving from cadmium pollution condition.The main results were as follows:(1)The tolerance limition of cadmium,copper,lead,nickel for pseudomonas aeruginosa were up to 900,100,100,30 mg·L-1 respectively.While the tolerance limition of compound pollution with cadmium mixing with copper,lead or nickel were up to 200,300,100 mg·L-1,respectively.(2)The bioassay experiments showed that the germination of seeds of Shanghai green,radish were not be inhibited by bacteria liquid(the density is 5.67×1012 CFU·mL-1),inactivated bacteria liquid,and bacteria cells which diluted more than 10 times and cultivated for 24h.This result indicated that the has no significant toxicity effects on the germination of tested plant seeds and growth of seedling.(3)To explore the application of Pseudomonas aeruginosa in bioremediation for heavy metal polluted environment,two particle sizes(1?3 mm and 3?6 mm)of diatomite,activated carbon and pumice were used as materials,and the carriers were screened by determing their performances of water absorption,bacteria adsorption and release,and the bacteria survival rate in bacterial agent.The results showed that the carrier of diatomite with particle size at 3-6 mm has moderate carring capacity,high bacteria survival rate,and higher living bacterium release rate,can be used as material for developing the bacterial agent of P.aeruginosa.The density of bacteria population released from prepared bacterial agent B were up to 28.8%.After preserved 30 d at room temperature,the bacterial populations in agent B was 1.12×1010 CFU·g-1that was 5.38 times as higher as that of initial value.(4)The result showed that root length,plant height and fresh weight of rice seedling were significantly suppressed by cadmium treated at 20?mol·L-1 in hydroponic experiments While the adding bacterial liquid and bacterium agent promoted the growth of root length,plant height and fresh weight of rice performing alleviated effect of rice polluted by cadmium.(5)The analysis of physiological and biochemistry activity showed that the bacterial agent can significantly improve the physiological activity of rice under Cd stress.The root vigor of rice treated with of bacteria agent A,bacteria agent B and bacterium agent C were 1.49,1.50,1.53 times as higher as that treated with Cd,the net photosynthetic rate were 2.52,2.57 and 2.37 times,soluble protein content in leaf were 1.60,1.73,1.38 times,SOD activity of leaf were 1.43,1.39,1.26 times and POD activity is 1.04,1.04,1.10 times as higher as that treated with Cd,respectively.The CAT activity is 1.14,1.08,1.12 times as higher as the control,and were 1.52,1.44,1.49 times as higher as the result treated by Cd stress.Furthermore,the MDA and O2content of rice leaf were significantly decreased,while the flavonoids and total phenol contents were greatly increased in rice leaf treated with Bacterialagent and agent A,B,C.In conclusion,the P.aeruginosa isolated from the rhizosphere soil of Cd tolerant rice has high heavy metal tolerance for single and composite pollution,and the prepared bacterium agent would not inhibit the germination of seeds,accompanying with promoting effect of the crop growth,and positive physiological response in rice under Cd stress in charge of relieve the stresses of cadmium in rice. |
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