【作者】 杨超；

【导师】 王春燕；

【作者基本信息】 西北农林科技大学 ， 森林保护学， 2018， 硕士

【摘要】 农田生态系统重金属污染日趋严重,危及我国粮食安全和国民健康。植物-微生物联合修复技术因具有投资小、环境友好等优越性已成为当下研究的热点。本论文以广泛种植的农作物水稻（Oryza sativa L.）为试验材料,在盆栽条件下研究了不同Pb²⁺质量浓度（0、250、500 mg/Kg基质）胁迫下分别接种2种深色有隔内生真菌（Dark septate endophytes,DSE）（Phialocephala fortinii和Phaeosphaeria fuckelii）对水稻生长的影响,并通过比较Pb²⁺胁迫下接种这2种DSE后水稻生理生化特性（光合作用、细胞膜脂氧化、根系活力、抗氧化酶系统和抗氧化物质）以及根际土pH、Pb²⁺吸收和转运的变化,分析DSE对水稻铅耐受性和水稻籽粒中铅含量的影响及潜在机制,为DSE在降低水稻籽粒铅含量中的应用以及重金属铅污染农田生态系统修复中的应用提供理论依据。主要研究结果如下:1.通过重金属铅抗性筛选和水稻根系侵染试验,从实验室保存的9种DSE中筛选出2种（P.fortinii和P.fuckelii）铅耐受性较强的菌株,且这2种DSE真菌均能与水稻形成良好的共生关系,因此被用作下一步试验的材料。2.与不接菌的对照相比,Pb²⁺胁迫下接种P.fortinii和P.fuckelii均能提高水稻的生物量,尤其能促进水稻的分蘖和根系的生长,而高浓度Pb²⁺胁迫下（500 mg/Kg）接菌对水稻的促生作用更为显著。表明接种DSE能缓解铅毒害对水稻生长的抑制,从而维持其正常生长。2种DSE相比较而言,Pb²⁺胁迫下,P.fortinii对水稻根系的侵染率较高,对植株生长的促进作用也较为突出。3.Pb²⁺胁迫下,不接菌水稻的净光合速率（Pn）、蒸腾速率（Tr）和气孔导度（Gs）降低,而叶片胞间CO₂浓度（Ci）升高。接种DSE缓解了Pb²⁺胁迫对水稻光合作用的抑制,其中对水稻Pn的提高作用最为显著,接种P.fortini和P.fuckelii后Pn分别提高了32.1%-86.8%和24.5-54.9%;而只在较高Pb²⁺浓度（500 mg/Kg）下接菌才对水稻的Tr和Gs有显著提高。此外,接种P.fortini使水稻叶片Ci降低了19.5-40%。Pb²⁺胁迫使水稻叶片细胞的膜脂受到损伤,导致丙二醛（MDA）含量激增,电解质外漏,而接种DSE可降低水稻叶片细胞中MDA含量和电解质透出率,从而减轻Pb²⁺毒害造成的细胞膜脂损伤。4.Pb²⁺胁迫下,接种P.fortinii使水稻叶片中的超氧化物歧化酶（SOD）活性提高了27.8%-185%,过氧化物酶（POD）活性提高了39%-64%;而P.fortinii和P.fuckelii接种水稻植株叶片中的过氧化氢酶（CAT）活性分别是对照的1.4-2.9倍和1.6-2.3倍,脯氨酸含量分别是对照的1.4-1.7倍和1.3-1.5倍。与对照相比,接种DSE也显著增强了水稻的根系活力,这可能也是DSE提高水稻铅耐受性的重要原因之一。5.无论接菌与否,重金属Pb²⁺胁迫下水稻各个组织器官中Pb²⁺富集量的大小依次是:根>叶片>籽粒。接种DSE后水稻根系中的Pb²⁺含量显著提高,而叶片和籽实中的Pb²⁺含量与对照相比则较低,表明接种DSE可通过影响重金属Pb²⁺在水稻体内的转运和分布而降低地上部分尤其是水稻籽粒中的Pb²⁺含量,从而缓解Pb²⁺的毒害作用。更多还原

【Abstract】 Heavy metal pollution in farmland ecosystems has become increasingly serious,threatening the grain security and national health of our country.Plant-microorganism combined remediation technology,which is environmental friendly and cheap,has become the focus of current research.In this study,a pot experiment was conducted to analyze the effect of two dark septate endophytes（DSE）（Phialocephala fortinii and Phaeosphaeria fuckelii）on Oryza sativa growth under different Pb²⁺concentrations（0,250,500 mg/Kg soil）.Moreover,the differences in physiological characteristics（photosynthesis,cell membrane lipid oxidation,root vigor,antioxidative enzyme systems and antioxidants）,pH value of rhizosphere soil,lead uptake and translocation of O.sativa were compared between DSE inocolated and uninoculated plants.Furthermore,the possible mechanism on DSE improving the lead tolerance of O.sativa was analyzed.This study could provide the theory basis for the application of DSE in the control and vegetation restoration of heavy metal lead pollutted farmland ecosystems.The main results and conclusions were listed as follows:1.Two DSE isolates,P.fortini and P.fuckelii,were screened from nine with higher lead tolerance and could establish a better symbiotic relationship with O.sativa root,and were used for the next step.2.Under lead stress,DSE inoculation could increase the biomass of O.sativa when compared with uninoculated plants,in particular,promote the tillering and root growth,higher lead stress,bigger improving effect.Compared to the effects of P.fuckelii,P.fortinii showed a better ability of promoting the growth of O.sativa under lead stress,which may be related to its higher colonization rate.3.The photosynthetic rate,transpiration rate and stomatal conductance of uninoculated plants were declined under lead press,but their intercellular carbon dioxide concentrations were increased.DSE inoculation showed a positive effect on the photosynthesis of O.sativa,especially on the net photosynthetic rate which were increased by 32.1%-86.8%and24.5-54.9%,respectively.Transpiration rate and stomatal conductance of O.sativa leaves were significant increased under higher lead stress.Moreover,the leaf intercellular carbon dioxide concentrations were reduced about 19.5-40%when inoculation with P.fortini.The membrane lipids of O.sativa leaf cells were damaged by lead stress,resulting in a rapid increase in malondialdehyde contents and leakage of electrolytes.DSE inoculation reduced the contents of malondialdehyde and electrolyte leakage in the leaf cells,so that the damage of membrane lipids caused by lead poisoning were declined.4.Under lead stress,the activities of superoxide dismutase（SOD）and peroxidase（POD）in two DSE inoculated O.sativa leaves were increased by 27.8%-185%and 39%-64%,respectively.In addition,P.fortini and P.fuckelii inoculation increased the activity of leaf catalase（CAT）by 1.4-2.9 fold and 1.6-2.3 fold,and the amount of leaf proline by 1.4-1.7 fold and 1.3-1.5 fold,respectively.Compared with uninoculated plants,mycorrhized O.sativa had a higher root vitality,which may be one of the most important reasons for the effect of DSE on improving the lead tolerance of O.sativa.5.Under lead stress,the lead concents in different organs of O.sativa were in roots>leaves>seeds.Compared with uninoculated plants,the lead contents in the DSE inoculated O.sativa roots were higher,but the lead contents in leaves and seeds were lower than those of control.This results showed that more lead content was accumulated in the DSE inoculated O.sativa roots,accompanied by the decrease in lead and seed lead contents.更多还原