氮肥形态与用量对水稻镉积累和毒害的影响及调控机制研究

发布时间：2018-06-08 14:15

本文选题：镉 + 水稻　；参考：《中国农业科学院》2016年博士论文

【摘要】：镉(Cadmium,Cd)是一种危害性极强的有毒重金属元素。通过工业生产、采矿、污水灌溉、施用劣质磷肥、大气沉降等途径进入农田土壤。Cd会对作物产生严重危害,可以导致代谢紊乱、营养缺失、抑制叶绿素合成、降低光合作用、产生氧化胁迫等,致使植物生长受阻,甚至死亡。更为重要的是,Cd会通过食物链富集在身体中,对人畜健康造成严重危害。稻米是人体Cd的重要来源,联合国粮食及农业组织规定Cd在可食用稻米中的含量不能超过0.1 mg/Kg,然而,Cd在稻米中的超标事实仍旧不容乐观。在众多降低水稻Cd积累的办法中,科学家一致认为营养调控是最经济、最省时、最有效的可用于降低稻米中Cd含量的方法。然而,氮肥作为水稻最重要的栽培措施,对水稻Cd吸收和积累以及毒害的影响及调控机制,尚未被研究清楚。本研究主要采用水培和盆栽方法,选用水稻品种日本晴,水培采用国际水稻研究所营养液配方,分别用标准浓度的硝态氮(Nitrate,NO_3~-)、铵态氮(Ammonium,NH_4~+)及酰胺态氮(Urea)肥,Cd浓度为100μM,于水稻分蘖期开展氮肥形态和用量对水稻Cd吸收和毒害的研究,结果表明:1、3种氮肥形态处理下水稻对Cd的吸收以及毒害症状不同。Cd胁迫下,NH_4~+处理水稻的分蘖、干重、光合速率、蒸腾速率、总氮含量较高,相比NO_3~-处理分别高49.1%、9.6%、106.5%、264.6%、48.3%;根部和地上部丙二醛含量、根部和地上部过氧化氢含量显著低约44.2%、18.9%、48.5%、36.5%;以植株生长、光合特性、营养元素吸收和氧化胁迫程度指标,说明NH_4~+减轻水稻Cd毒害的能力显著高于Urea和NO_3~-。另外,3种氮肥形态处理对水稻Cd的吸收和积累影响不同,其中NO_3~-处理的水稻植株Cd吸收能力最强,NO_3~-处理的水稻根部Cd含量是NH_4~+处理的2.79倍,其次是Urea,最后是NH_4~+。2、过量NO_3~-通过Fe转运系统间接促进了水稻对Cd的吸收和积累。采用水培和土培方法,施用不同浓度的NO_3~-处理水稻。结果表明,过量NO_3~-增加了水稻根尖伸长区的Cd2+流通量,相比对照增加53.2%,过量NO_3~-处理的水稻,其根部、地上部及稻米中的Cd含量分别比对照高出8.0%、67.0%、93.0%,而缺NO_3~-显著降低了Cd2+流通量及Cd在植株各部位的积累。进一步研究表明,过量NO_3~-上调了根尖Fe转运体Os IRT1基因的表达,致使水稻根部和地上部Fe含量分别增加13.5%和59.9%。因此,过量的NO_3~-增加了稻米Cd毒害风险,建议在Cd污染稻区避免大量施用NO_3~-肥。3.过量NH_4~+通过调节根部金属螯合肽含量及抗氧化物酶活性减轻了水稻Cd毒害。在水培条件下,采用不同浓度的NH_4~+肥处理3周大的水稻品种日本晴,结果发现,Cd胁迫下过量NH_4~+显著增加了水稻株高、叶绿素a含量、叶绿素b含量、光合速率、地上部氮含量,增幅分别为4.7%、17.8%、27.1%、28.0%、7.9%,而缺NH_4~+显著降低了这些指标。进一步研究表明,过量NH_4~+处理下,水稻根部硫含量和硫积累量分别增加了17.8%和17.4%,根部金属螯合肽含量增加了6.8%,水稻Cd毒害减轻。另外,过量NH_4~+显著降低了水稻根部和地上部丙二醛含量、根部过氧化氢含量,其降幅分别为13.4%、13.2%、23.9%,缺NH_4~+显著增加了胁迫程度。同时,过量NH_4~+显著上调了根部Os MT-1基因、地上部Os LCD基因的表达。过量NH_4~+增加了根部和地上部过氧化物酶(POD)和地上部抗坏血酸氧化酶(APX)活性,增幅分别为31.3%、35.3%、12.6%。因此,过量NH_4~+提高了水稻POD和APX活性,减轻了水稻Cd毒害。4.过量NH_4~+促进了Cd向水稻地上部的转运。过量NH_4~+处理的水稻地上部/根部Cd含量比增加了14.5%,而缺NH_4~+显著降低了这一转运比率。另外,过量NH_4~+显著下调了水稻根部Os HMA3基因表达,减少了螯合肽Cd向液泡中的固定,因此,NH_4~+通过下调根部Os HMA3基因表达增加了水稻植株Cd向地上部的转运。5.酰胺态氮(Urea)能通过上调水稻Cd吸收和转运基因的表达增加Cd的积累。采用不同浓度的Urea处理水稻,过量Urea处理下水稻根部硝态氮、硝铵比均增加,同时也上调了根部Os Nramp1、Os Nramp5和Os HMA2基因的表达,增加了水稻根部和地上部Cd的含量,而缺Urea降低了这些指标。氮肥形态与用量对水稻Cd吸收和毒害的影响及其调控机制研究,对水稻生产与稻米安全具有重要的理论和实际意义。本研究以水稻最常用的3种氮肥形态和用量,研究水稻Cd吸收、积累及毒害的生理及分子机制,为水稻Cd危害调控技术提供理论支持,同时也为Cd污染稻区氮肥管理提供参考。
[Abstract]:Cadmium (Cd) is a toxic heavy metal element which is very harmful. Through industrial production, mining, sewage irrigation, application of poor quality phosphorous fertilizer and atmospheric sedimentation,.Cd will have serious harm to crops, which can lead to metabolic disorder, nutrient loss, inhibition of chlorophyll synthesis, photosynthesis, oxidative stress and so on. Plant growth is blocked, even death. More importantly, Cd will be enriched in the body through the food chain, causing serious harm to human and animal health. Rice is an important source of human Cd. The United Nations Food and agricultural organization stipulates that the content of Cd in edible rice can not exceed 0.1 mg/ Kg, however, the excess of Cd in rice is still not allowed. In many ways to reduce the accumulation of rice Cd, scientists agree that nutrition regulation is the most economical, most time-saving and most effective method to reduce the Cd content in rice. However, as the most important cultivation measure of rice, the effect on the absorption and accumulation of Cd and the effects of toxic damage and regulation mechanism of rice have not been clearly studied. The study mainly used hydroponics and pot culture to choose rice variety Japan and the nutrient solution formula of International Rice Research Institute in water culture. The standard concentration of nitrate nitrogen (Nitrate, NO_3~-), ammonium nitrogen (Ammonium, NH_4~+) and amide nitrogen (Urea) fertilizer were used respectively. The concentration of Cd was 100 u M, and the nitrogen form and amount of nitrogen fertilizer were used to absorb the Cd absorption of rice at the tillering stage of rice. And the results of the toxicity study showed that under the treatment of 1,3 nitrogen fertilizer, the absorption of rice to Cd and the toxic symptoms of different.Cd stress, NH_4~+ treated rice with higher tillering, dry weight, photosynthetic rate, transpiration rate and total nitrogen content, which was 49.1%, 9.6%, 106.5%, 264.6%, 48.3% higher than that of NO_3~-, and the content of malondialdehyde in root and upper part of the ground, and the root and root. The content of H2O2 in the upper part of the ground was significantly lower than 44.2%, 18.9%, 48.5%, 36.5%. The plant growth, photosynthetic characteristics, nutrient absorption and oxidative stress levels showed that the ability of NH_4~+ to reduce the Cd toxicity of rice was significantly higher than that of Urea and NO_3~-., and the effects of 3 nitrogen fertilizer treatments on the absorption and accumulation of Cd in rice were different, of which NO_3~- treatment was treated. The Cd absorpability of rice plants was the strongest. The Cd content in root of NO_3~- treated rice was 2.79 times that of NH_4~+, followed by Urea, and finally NH_4~+.2. Excessive NO_3~- through Fe transport system indirectly promoted the absorption and accumulation of rice to Cd by the method of hydroponics and soil culture. The results showed that excessive NO_3~- increased. The Cd2+ circulation in the root tip elongation area of rice was increased by 53.2% compared with the control. The Cd content in the root, the upper and the rice was 8%, 67%, 93% higher in the root, the upper and the rice than the control, respectively, while the lack of NO_3~- significantly reduced the Cd2+ circulation and the accumulation of Cd at the plant parts. Further studies showed that excess NO_3~- increased the root tip F. The expression of the Os IRT1 gene in the e transporter resulted in the increase of 13.5% and 59.9%. in the rice root and the upper part of the ground, so the excess NO_3~- increased the risk of Cd toxicity in rice. It was suggested that a large amount of NO_3~- fertilizer.3. is avoided in Cd polluted rice area, and.3. excess NH_4~+ by regulating the content of the metal chelating peptide and the activity of antioxidant enzymes alleviated the rice Cd poison. Under the condition of hydroponics, using NH_4~+ fertilizer of different concentrations to treat the rice variety of 3 weeks large rice, the results showed that excessive NH_4~+ under Cd stress increased rice plant height, chlorophyll a content, chlorophyll b content, photosynthetic rate, and upper nitrogen content, respectively, increased by 4.7%, 17.8%, 27.1%, 28%, 7.9%, and the lack of NH_4~+ significantly reduced these Further studies showed that the sulfur content and sulfur accumulation in root of rice increased by 17.8% and 17.4% respectively under excessive NH_4~+ treatment, the content of metal chelating peptide in root increased by 6.8%, and the toxicity of rice Cd decreased. In addition, excess NH_4~+ significantly reduced the content of malondialdehyde in root and shoot of rice and the content of hydrogen peroxide at root, and the decrease was 13.4, respectively. %, 13.2%, 23.9%, the lack of NH_4~+ significantly increased the degree of stress. At the same time, excessive NH_4~+ significantly up-regulated the Os MT-1 gene in the root and the expression of Os LCD gene in the upper part of the ground. The excess NH_4~+ increased the viability of the peroxidase (POD) and the upper ascorbic acid oxidase (APX) in the root and the upper part of the ground, and the increase was 31.3%, 35.3%, and 12.6%. therefore, the excess NH_4~+ increased The activity of POD and APX in rice reduced the Cd toxicity of rice to.4. over NH_4~+ to promote the transport of Cd to the upper part of the rice ground. The ratio of Cd content in the upper / root of rice increased by 14.5%, while the deficiency of NH_4~+ significantly reduced the rate of transport. In addition, excessive NH_4~+ significantly reduced the Os HMA3 gene expression in the roots of rice and reduced chelation. Peptide Cd was immobilized to the vacuole, so NH_4~+ increased the transport of Cd to the upper part of the rice plant by downregulating the Os HMA3 gene expression in the roots, and increased the accumulation of Cd by increasing the expression of.5. amido nitrogen (Urea) in the upper part of the rice plant (Urea) by up regulating the expression of the rice Cd absorption and transport genes. The nitrate nitrogen and ammonium nitrate nitrogen, ammonium nitrate, in the root of the rice were treated by excessive Urea, and ammonium nitrate was treated with a different concentration of Urea. It also increased the expression of Os Nramp1, Os Nramp5 and Os HMA2 gene in root, increased the content of Cd in the root of rice and the Cd in the upper part of the rice, and the lack of Urea reduced these indexes. The effect of nitrogen form and dosage on the Cd absorption and toxicity of rice and its regulation mechanism are important theory and reality for rice production and rice safety. In this study, the physiological and molecular mechanisms of rice Cd absorption, accumulation and toxicity are studied with the 3 most commonly used nitrogen forms and amounts in rice, which provide theoretical support for the regulation of rice Cd hazards and provide a reference for the management of nitrogen fertilizer in the rice area of Cd.
【学位授予单位】：中国农业科学院
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S511

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