水稻挥发汞及调控因素研究

发布时间：2018-04-09 07:13

  本文选题：水稻　切入点：气态单质汞　出处：《华东师范大学》2017年硕士论文

【摘要】：湿地是汞的重要富集场所,其还原性底质会促进气态单质汞的产生。本研究以水稻这一典型的湿地植物为例,研究其根系及通气组织是否也能成为根际气态汞向大气运输的通道,并探究其机制和影响因素。论文通过设计密闭分室培养装置将水稻根部与地上部分隔开,对水稻根部进行汞蒸气暴露,并通过气体吸收剂吸收由叶片挥发出的气态汞。论文还通过铁膜诱导和营养元素胁迫培养方法,研究阐明铁膜对汞挥发的调控作用和机理,及营养元素缺乏对水稻吸收和挥发气态单质汞的影响。研究结果表明:(1)水稻可以从根系吸收气态单质汞并向地上组织迁移,其中根系的汞含量与水稻根孔隙度呈显著负相关,并呈二次拟合(R=0.8309,P0.01);而水稻地上部汞迁移量与水稻根表面积和根体积均呈线性正相关(R=0.896,P0.01;R=0.871,P0.01)。研究还发现由根系吸收的汞最终可通过水稻叶片挥发进入大气,叶片汞的挥发量随着叶片面积的增加呈线性增加(R=0.897,P0.01),单位叶面积汞挥发量与水稻蒸腾作用强度呈线性显著正相关(R=0.73,P0.01)。(2)不同基因型之间,根表铁膜的生成量具有显著性差异(P0.05),在同样的培养条件下,籼稻的根系铁膜生成量明显高于粳稻。水稻根表铁膜可吸附气态单质汞。籼稻根表铁膜对气态单质汞的吸附量均明显高于粳稻(P0.05),其吸附量与水稻的根表铁膜生成量呈显著正相关(R=0.701,P0.01)。水稻根表铁膜可显著减少水稻根系对气态单质汞的吸收,并降低水稻地上部汞的迁移和水稻叶片汞的挥发。(3)在氮、磷营养缺乏胁迫下,水稻生长受到不同的影响。其中缺氮处理抑制了水稻根与叶的生长。与正常组进行对比,我们发现氮胁迫的三种水稻的根表面积、根长、根体积和根干重均有下降,而水稻的根孔隙度则显著增加(P0.05),且其叶面积和地上部干重也随着氮浓度的降低而减少。我们发现氮胁迫降低了水稻对气态单质汞的吸收、转运和挥发。与之相反,缺磷则促进了水稻根和叶的生长,且磷胁迫使水稻根系汞含量和地上部汞转运量先降低后增加。在磷胁迫的条件下,三种基因型水稻叶片的汞挥发量略有差异。水稻Ⅱ优1259和武运粳21号随着磷浓度的降低,叶片汞挥发量也随之减少,且与对照组呈显著性差异(P0.05),而粳稻屉优267水稻叶片汞挥发量只是略微减少,并不与对照组呈显著性差异(P0.05)。以上研究结果证明了水稻根系不仅能吸收气态单质汞,并且能将汞从根部转运到地上部,再通过叶片的气孔释放到空气中。研究结果为进一步揭示湿地生态系统中汞的迁移及调控机理提供了科学依据。
[Abstract]:Wetland is an important enrichment site of mercury, and its reductive sediment can promote the production of gaseous elemental mercury.In this study, rice, a typical wetland plant, was used as an example to study whether the root system and aerated tissue could also be used as a pathway for the transport of gaseous mercury to the atmosphere, and to explore its mechanism and influencing factors.In this paper, a closed chamber culture device was designed to separate the roots of rice from the aboveground parts, and to expose the roots to mercury vapor, and to absorb the gaseous mercury volatilized from the leaves by gas absorbent.The regulation and mechanism of Fe film on mercury volatilization and the effect of nutrient element deficiency on the absorption and volatilization of elemental mercury in rice were also studied by the methods of iron film induction and nutrient element stress culture.The results showed that rice could absorb gaseous elemental mercury from the root system and migrate to the aboveground tissue, and the root mercury content was negatively correlated with the root porosity.There was a linear positive correlation between the aboveground mercury transport and root surface area and root volume.The study also found that mercury absorbed by the root system can eventually volatilize into the atmosphere through rice leaves.The leaf mercury volatilization increased linearly with the increase of leaf area. There was a significant linear correlation between the Hg volatilization per leaf area and the transpiration intensity of rice.There was significant difference in the amount of iron film produced in root surface. Under the same culture conditions, the iron film production in the root of indica rice was significantly higher than that in japonica rice.Rice root surface iron film can adsorb gaseous elemental mercury.The adsorption capacity of gas elemental mercury in indica rice root surface iron film was significantly higher than that in japonica rice (P0.05A), and there was a significant positive correlation between the adsorption amount and the root surface iron film formation.Iron film on the root surface of rice could significantly reduce the absorption of gaseous elemental mercury by the root system, and decrease the migration of mercury in the aboveground part of rice and the volatilization of mercury in the leaves of rice.) under the stress of nitrogen and phosphorus deficiency, the growth of rice was affected by different factors.Nitrogen deficiency inhibited the growth of rice roots and leaves.Compared with the normal group, we found that the root surface area, root length, root volume and root dry weight of the three kinds of rice under nitrogen stress decreased.The root porosity of rice increased significantly, and the leaf area and dry weight of shoot decreased with the decrease of nitrogen concentration.We found that nitrogen stress reduced the absorption, transport and volatilization of gaseous elemental mercury in rice.On the contrary, P deficiency promoted the growth of roots and leaves of rice, and phosphorus stress decreased the content of mercury in root and then increased the amount of mercury transport in shoot.Under phosphorus stress, there was a slight difference in mercury volatilization in leaves of three genotypes of rice.With the decrease of phosphorus concentration in rice 鈪，

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