【作者】 杨宇；

【导师】 杨丹；

【作者基本信息】 沈阳农业大学 ， 环境工程， 2023， 硕士

【摘要】 硅对水稻生长和缓解砷毒害具有积极作用,因此砷污染土壤的硅素养分供应状况是影响水稻生长发育的重要因素。已有研究表明,充足的硅素营养可以通过和砷形成竞争吸收从而抑制水稻吸收三价砷,但相关的根际效应与机制研究尚不系统和明确。本文以有效硅含量不同的砷污染土壤（Si0、Si50、Si100、Si150）为研究对象,以水稻为供试作物,采取盆栽试验、化学分析及高通量测序技术相结合的方法,系统地研究了砷胁迫条件下施硅对水稻生长与砷吸收的影响,分析了根表铁膜数量、组分及其固砷量的变化,探讨了不同处理根际土壤细菌群落组成及铁氧化细菌丰度的差异,为揭示硅缓解水稻砷毒害的根际化学和微生物学机制提供了重要数据和理论支持。主要研究结果和结论如下:1.砷胁迫条件下,土壤硅素养分的增加可促进水稻的生长发育和结实。各砷胁迫处理水稻地上、地下部生物量及产量均表现为Si150>Si100>Si50>Si0;尤其是Si100和Si150两个处理与对照CK（无砷污染）处理间的差异不显著,砷对水稻生长发育的抑制得到了缓解和改善。2.砷胁迫条件下,土壤硅素养分的增加可促进水稻吸收转运硅和磷,抑制水稻吸收砷。与对照CK相比,Si0处理水稻茎叶和稻壳的硅含量分别下降了35.90%和25.17%,磷含量下降了15.58%和33.33%,与CK的差异分别达到5%和1%显著水平。砷胁迫条件下,土壤有效硅含量水平较高的Si50、Si100和Si150三个处理水稻茎叶、稻壳和糙米的砷含量均明显低于有效硅含量水平较低的Si0处理,且以Si100处理效果最明显（P<0.01）,分别比Si0处理降低了27.80%、35.74%和21.21%,其次为Si50处理。3.砷胁迫条件下,土壤硅素养分的增加可促进水稻根表铁膜的形成及其对砷的固定。各处理水稻根表铁膜组分中,IP₁（菱铁矿和铁镁石）和IP₂（水铁矿和纤铁矿）含量较高,两组分之和占铁膜总量的91%-95%,是铁膜固砷作用的主要贡献组分;IP₃（针铁矿、四方纤铁矿和赤铁矿）和IP₄（磁铁矿）含量较少,分别占总量的5%-7%和1%-2%。各砷胁迫处理水稻根表铁膜总量表现为Si150>Si100>Si50>Si0,Si50、Si100和Si150处理铁膜总量分别比Si0增加了24.29%、55.45%和99.86%,铁膜砷含量分别增加了33.54%、142.30%和108.67%,但Si50与Si0差异不显著。砷胁迫条件下土壤有效硅含量与水稻根表铁膜总量、铁膜砷含量之间分别存在显著线性正相关和二次函数关系。4.砷胁迫改变了水稻根际土壤的细菌群落组成和结构,适宜提高土壤硅素养分含量可恢复根际土壤细菌群落组成和多样性,促进铁转化相关菌属丰度增加。与对照CK相比,砷胁迫条件下根际土壤细菌群落多样性指数、丰富度指数和均匀度指数均下降;Si100处理细菌alpha多样性和Beta多样性恢复程度最高,其与CK处理共有的ASV/OUT数为461个,明显高于其他砷胁迫处理。Si100处理丰度最高的菌属为Sideroxydans（铁氧化菌属）和Geobacter（铁还原菌属）,Thiobacillus（硫化菌属）丰度也明显提高。综上,砷胁迫条件下,适当施硅可促进水稻生长发育,同时可导致根际土壤细菌群落组成的多样性提高,铁氧化、还原相关菌属相对丰度增加,根表铁膜数量及其固砷量增加。施硅增强根表铁膜形成及其固砷作用是其缓解水稻砷毒害的重要机制之一。更多还原

【Abstract】 Silicon has a positive effect on rice growth and mitigation of arsenic toxicity,so silicon nutrient supply in arsenic-contaminated soil is an important factor affecting rice growth and development.Previous studies have shown that sufficient silicon nutrition can inhibit the uptake of trivalent arsenic in rice by competing with arsenic for uptake,but the related rhizosphere effects and mechanisms are not yet systematic and clear.In this paper,arsenic-contaminated soils（Si0,Si50,Si100,and Si150）with different available silicon contents were taken as the research object,rice was used as the test crop,and pot experiments,chemical analysis,and high-throughput sequencing techniques were used to systematically study The effects of silicon fertilization on rice growth and arsenic uptake under arsenic stress conditions were analyzed,the changes in the number,composition and arsenic fixation of root surface iron films were analyzed,and the composition of bacterial communities in rhizosphere soil and the abundance of iron-oxidizing bacteria were discussed.These differences provide important data and theoretical support for revealing the rhizosphere chemical and microbiological mechanisms of silicon in alleviating arsenic toxicity in rice.The main research findings and conclusions are as follows:1.Under the condition of arsenic stress,the increase of soil silicon nutrient can promote the growth and fruiting of rice.The biomass and yield of the aboveground and underground parts of rice in each arsenic stress treatment were Si150>Si100>Si50>Si0;especially the difference between Si100 and Si150 treatments and the control CK（no arsenic pollution）treatment was not significant,and the effect of arsenic on rice Growth inhibition was alleviated and improved.2.Under the condition of arsenic stress,the increase of soil silicon nutrient can promote the uptake and transport of silicon and phosphorus in rice,and inhibit the uptake of arsenic in rice.Compared with the control CK,the silicon content of rice stems,leaves and rice husks treated with Si0 decreased by 35.90%and 25.17%,respectively,and the phosphorus content decreased by 15.58%and 33.33%,and the differences from CK reached 5%and 1%significant levels,respectively.Under arsenic stress,the arsenic content of rice stems,leaves,rice husks and brown rice in Si50,Si100 and Si150 with higher soil available silicon content were significantly lower than those in Si0 treatment with lower available silicon content,and Si100 treatment The effect was the most obvious（P<0.01）,which was 27.80%,35.74%and21.21%lower than Si0 treatment,followed by Si50 treatment.3.Under the condition of arsenic stress,the increase of soil silicon nutrient can promote the formation of iron film on rice root surface and its fixation of arsenic.Among the iron mantle components on the rice root surface in each treatment,the contents of IP₁（siderite and ferrite）and IP₂（ferrihydrite and lepidocite）were relatively high,and the sum of the two components accounted for 91%of the total iron mantle.95%,which is the main component contributing to the arsenic fixation of the iron film;IP₃（goethite,lepidographite and hematite）and IP₄（magnetite）are relatively small,accounting for 5%-7 of the total%and 1%-2%.The total amount of iron film on the rice root surface under each arsenic stress treatment was Si150>Si100>Si50>Si0.Increased by 33.54%,142.30%and 108.67%,but the difference between Si50 and Si0 is not significant.Under the arsenic stress condition,there were significant linear positive correlation and quadratic function relationship between soil available silicon content,total iron film on rice root surface,and arsenic content in iron film,respectively.4.Arsenic stress changed the composition and structure of the bacterial community in the rice rhizosphere soil.Properly increasing the soil silicon nutrient content can restore the composition and diversity of the bacterial community in the rhizosphere soil,and promote the increase in the abundance of bacterial genera related to iron transformation.Compared with the control CK,the diversity index,richness index,and evenness index of the rhizosphere soil bacterial community decreased under the arsenic stress condition;the bacterial alpha diversity and beta diversity recovery degree of the Si100 treatment was the highest,and the ASV common to the CK treatment The number of/OUT was 461,significantly higher than other arsenic stress treatments.The genera with the highest abundance in Si100 treatment were Sideroxydans（iron-oxidizing bacteria）and Geobacter（iron-reducing bacteria）,and the abundance of Thiobacillus（sulfurizing bacteria）was also significantly increased.In summary,under arsenic stress conditions,appropriate silicon application can promote the growth and development of rice,and at the same time lead to an increase in the diversity of rhizosphere soil bacterial communities,an increase in the relative abundance of iron oxidation and reduction-related bacterial genera,and the number of iron films on the root surface and their relative abundance.The amount of arsenic fixation increased.Silicon application enhances the formation of iron film on the root surface and its arsenic fixation is one of the important mechanisms for alleviating arsenic toxicity in rice.更多还原