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植物促生菌与CO2联合作用对商陆和籽粒苋富集铯的影响及其相关机理研究

The Effect of Plant Growth-promoting Bacteria (PGPB) and CO2 on Cs Uptake by P. americana Linn. and A. Cruentus L. and Related Mechanisms

【作者】 廖上强

【导师】 唐世荣;

【作者基本信息】 中国农业科学院 , 土壤学, 2011, 博士

【摘要】 随着核工业的发展和核技术的广泛应用,核爆试验或核泄漏事故等,使放射性核素不可避免的进入环境,这些放射性核素进入环境(大气、水体和土壤)后,对生态环境和人类健康造成潜在的危害,其中半衰期长、生成率高的137Cs,被认为生物学上最危险的放射性核素之一。治理核素污染的常规的物理、化学和工程等方法由于成本高,易造成二次污染,且难以用于治理环境中大面积污染。植物修复具有较好的应用前景,但它存在修复效率低、周期长等局限性。如何增加单位面积上植物生物量、对放射性核素的吸收量以提高植物修复的相对效率成为人们关注的焦点。接种微生物是重要的辅组手段,另一方面,大气CO2浓度升高增加植物对矿质养分的吸收,促进植物生长。因此,研究大气CO2浓度升高与微生物联合作用对植物吸收重金属或放射性核素污染物的影响成为一个新的研究热点。本文选择一株具有多种重金属(铅、镉、铜、锌)抗性且能产生植物生长激素、固氮、溶解难溶性无机磷等性质的植物促生菌Burkholderia sp.D54,进行解钾、耐铯、富集铯能力研究,并在此基础上通过水培和土培盆栽试验研究接种Burkholderia sp.D54和CO2浓度升高植物对Cs吸收的影响,并从植物根系形态、钾的吸收、植物光合速率、叶绿素含量、抗氧化酶活性等探讨其可能性机制。选题具有重要的理论意义与实用价值。得出以下主要结论:(1)耐重金属的Burkholderia sp.D54对Cs表现出较强的耐性,在培养基铯含量达到50mM时能生长;100 mL养液中,接种1 mL母液(1.8×107cfu·mL-1)培养3天后可获得0.1737g菌体干物重。伯克氏菌细胞可以富集大量的铯,细胞对铯富集量达到45±3.85 mg·g-1(干重菌体),培养液中的铯去除率达到58.77%。(2)伯克氏菌Burkholderia sp.D54能分泌大量有机酸,培养4天后培养液pH值从6.5降致2.5,在含云母的培养液中接种Burkholderia sp.D54能有效溶解云母中的钾,相比不接种试验,培养液中钾含量显著增加。(3)水培籽粒苋接种Burkholderia sp.D54增加籽粒苋的生物量和铯的吸收量,大多未达到显著水平,但提高籽粒苋对铯的耐性指数和富集系数,一定程度上提高了籽粒苋对铯的修复效率。抗生素氨苄青霉素影响籽粒苋生长,植物与微生物联合试验中,添加氨苄青霉素作为微生物对照处理对不同植物影响不一样,应该先进行植物影响试验。(4)正常CO2浓度土培试验中,接种Burkholderia sp.D54美洲商陆和籽粒苋总生物量(干物重)分别比增加19.8%33.4%和22.9%76.6%;大气CO2浓度升高土培试验中,接种Burkholderia sp.D54美洲商陆和籽粒苋总生物量分别增加22%139%和14%254%。(5)正常CO2浓度土培试验中,接种Burkholderia sp.D54美洲商陆和籽粒苋地上部铯含量分别增加4.9%22.4%和8.1%19.4%,根中铯含量分别增加6.8%15.7%和1.1%10.8%;大气CO2浓度升高土培试验中,接种Burkholderia sp.D54美洲商陆和籽粒苋地上部铯含量分别增加10%47%和32%46%,根中铯含量分别增加27%56%和35%38%。(6)土壤中的铯抑制植物对钾的吸收,钾参与植物叶绿素的合成,从而影响植物叶绿素含量和光合反应速率,正常大气CO2浓度和CO2浓度升高条件下,接种Burkholderia sp.D54增加了植物对钾的吸收,从而提高植物叶绿素含量,提高植物净光合速率Pn、气孔导度Gs、胞间CO2浓度Ci、蒸腾速率E和水分利用率WUE,植物生物量增加可能与这些作用有关。(7)铯胁迫条件下,美洲商陆和籽粒苋叶片中的MDA含量显著升高;正常大气CO2浓度和CO2浓度升高条件下,接种Burkholderia sp.D54增加美洲商陆和籽粒苋抗氧化胁迫SOD、CAT、POD酶的活性,降低植物叶片中MDA含量,降低了美洲商陆和籽粒苋铯的氧化胁迫。

【Abstract】 Rapid development of nuclear industry and nuclear technologies in past few decades, nuclear explosion experiments or nuclear leakage accident, radionuclides have made the environment inevitably, posing potential harm to the ecological environment and human health. Due to long half-time and high uptake rate 137Cs was considered to be one of the most dangerous radionuclides. As for treatment of radionuclides pollution, the conventional physical and chemical and engineering methods cost high, secondary pollution, and diffical in treating large scale. With the development of modern bio-technology, the bio-remediation of the radionuclide is receiving more attention. The bio-remediation includes microorganism remediation and phytoremediation. There are many anti-radionuclide microorganisms in the nature, and some of them could accumulate and precipitate the radionuclide. Microorganism remediation is used in treatment of the wastewater nuclear power station, whereas, phytoremediation is widely used in the soil contamination with good performance. However, phytoremediation has some disadvantages, such as low efficientyand long period. Therefore how to increase the plant biomass in the per-unit area and the uptake of the radionuclides in order to improve the remediation efficiency is receiving attention. On the other hand, we are facing atmospheric CO2 rise which is considered to be one of the major environmental problems. It is universally acknowledged that, elevated atmospheric CO2 effect of enhance the mineral nutrient uotake by plants, and improve growth. So, the study of the increasing CO2 concentration on plant uptake of heavy metal or radionuclides, increasing remediation efficiency has becomes a new hot research topic.With the inspiration of elevated CO2 as an asisitend remediation agent, the present paper use one growth-promoting bacteria Burkholderia sp.D54, this micro-organism is heavy metal (Pb, Cd, Cu and Zn) resistence and plant growth hormone production, nitrogen fixation, dissolving of inorganic phosphate. We investigated is Cs resistance and accumulation ability, we also investigated the Cs uptake effect of elevated CO2-plant-microorganism combination, and the possible mechanism through plant root morphology, the uptake potassium, photosynthetic rate, The content of chlorophyll, activities of antioxidase and so on. The main conclusions are as follows:(1)The heavy metal resistance bacteria Burkholderia sp.D54 showed the tolerence to Cs, and could growh in the culture medium with the content of Cs 50mM; in the 100 mL culture medium, inoculated in 1 mL mother liquor(1.8×107cfu·mL-1), after 3 days produced the 0.1737g bacteria dry weight. The cell of Burkholderia sp.D54 was able to accumulate large quantities of Cs, being up to 45±3.85 mg·g-1(dry weight), and the removing rate of Cs was 58.77% after 3 days.(2)after the 4 days inoculation Burkholderia sp.D54 could secrete large quantities organic acid with pH being down from 6.5 to 2.5; inoculation in the mica culture medium, show that the microgrgainsm could dissolve the potassium efficiently, leading to increasing potassium concentration efficiently.(3)Inoculation of the bacteria to the hydroponic A. crenentus, could increase the A. crenentus biomass and the absorption of Cs, but most of them are not significantly. The resistance index and enrichment coefficient were improved, and the remediation efficiency to some extent. The antibiotic ampicillin affected the growth of A. crenentus, in the plant and bacteria combined experiment, added ampicillin as the CK treatment, different effect on the different plant, should do the plant effect experiment first.(4)In the soil pot experiment in the ambient CO2, inoculation of Burkholderia sp.D54, increased the total biomass of P. americana and A. crenentus (dry weight) by 19.8%33.4% and 22.9%76.6%, respectively. Elevated CO2, increased the total biomass of P. americana and A. crenentus by 22%139% and 14%254%, respectively.(5)In the pot experiment under the ambient CO2, inoculation of Burkholderia sp.D54, increased the Cs concentration in shoot of P. americana and A. crenentus by 4.9%22.4% and 8.1%19.4%, The Cs concentration in root was increased by 6.8%15.7% and 1.1%10.8%, respectively. Under the elevated CO2, Cs concentration in shoot of P. americana and A. crenentus increased by 10%47% and 32%46%, whereas in root of P. americana and A. crenentus by 27%56% and 35%38%, respectively.(6)Cs in the soil inhibited plant of uptake potassium, that has function of participation of in plant chlorophyll synthesis, and therefore affect the content of chlorophyll and photosynthetic rate. Under ambient CO2 and elevated CO2, inoculation of Burkholderia sp.D54 improved the plant uptake potassium, and increased the content of chlorophyll, enhanced the plant net photosynthetic rate Pn, stomatal conductance (Gs), intercellular CO2 concentration (Ci) transpiration rate (E) and water use efficiency (WUE), the increased of the biomass might contribute to these effection.(7)Under the stress of Cs, MDA concentration in leaves of P. americana and A. crenentus was significantly increased; Under ambient CO2 and elevated CO2, inoculation of Burkholderia sp.D54 inceresed Antioxidant SOD、CAT、POD enzyme activities of P. americana and A. crenentus, but decreased MDA contents in leaves of P. americana and A. crenentus .

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