本文選題：鎘 + 水稻�。� 參考：《中國(guó)農(nóng)業(yè)科學(xué)院》2016年博士論文

【摘要】：鎘(Cadmium,Cd)是一種危害性極強(qiáng)的有毒重金屬元素。通過工業(yè)生產(chǎn)、采礦、污水灌溉、施用劣質(zhì)磷肥、大氣沉降等途徑進(jìn)入農(nóng)田土壤。Cd會(huì)對(duì)作物產(chǎn)生嚴(yán)重危害,可以導(dǎo)致代謝紊亂、營(yíng)養(yǎng)缺失、抑制葉綠素合成、降低光合作用、產(chǎn)生氧化脅迫等,致使植物生長(zhǎng)受阻,甚至死亡。更為重要的是,Cd會(huì)通過食物鏈富集在身體中,對(duì)人畜健康造成嚴(yán)重危害。稻米是人體Cd的重要來源,聯(lián)合國(guó)糧食及農(nóng)業(yè)組織規(guī)定Cd在可食用稻米中的含量不能超過0.1 mg/Kg,然而,Cd在稻米中的超標(biāo)事實(shí)仍舊不容樂觀。在眾多降低水稻Cd積累的辦法中,科學(xué)家一致認(rèn)為營(yíng)養(yǎng)調(diào)控是最經(jīng)濟(jì)、最省時(shí)、最有效的可用于降低稻米中Cd含量的方法。然而,氮肥作為水稻最重要的栽培措施,對(duì)水稻Cd吸收和積累以及毒害的影響及調(diào)控機(jī)制,尚未被研究清楚。本研究主要采用水培和盆栽方法,選用水稻品種日本晴,水培采用國(guó)際水稻研究所營(yíng)養(yǎng)液配方,分別用標(biāo)準(zhǔn)濃度的硝態(tài)氮(Nitrate,NO_3~-)、銨態(tài)氮(Ammonium,NH_4~+)及酰胺態(tài)氮(Urea)肥,Cd濃度為100μM,于水稻分蘗期開展氮肥形態(tài)和用量對(duì)水稻Cd吸收和毒害的研究,結(jié)果表明:1、3種氮肥形態(tài)處理下水稻對(duì)Cd的吸收以及毒害癥狀不同。Cd脅迫下,NH_4~+處理水稻的分蘗、干重、光合速率、蒸騰速率、總氮含量較高,相比NO_3~-處理分別高49.1%、9.6%、106.5%、264.6%、48.3%;根部和地上部丙二醛含量、根部和地上部過氧化氫含量顯著低約44.2%、18.9%、48.5%、36.5%;以植株生長(zhǎng)、光合特性、營(yíng)養(yǎng)元素吸收和氧化脅迫程度指標(biāo),說明NH_4~+減輕水稻Cd毒害的能力顯著高于Urea和NO_3~-。另外,3種氮肥形態(tài)處理對(duì)水稻Cd的吸收和積累影響不同,其中NO_3~-處理的水稻植株Cd吸收能力最強(qiáng),NO_3~-處理的水稻根部Cd含量是NH_4~+處理的2.79倍,其次是Urea,最后是NH_4~+。2、過量NO_3~-通過Fe轉(zhuǎn)運(yùn)系統(tǒng)間接促進(jìn)了水稻對(duì)Cd的吸收和積累。采用水培和土培方法,施用不同濃度的NO_3~-處理水稻。結(jié)果表明,過量NO_3~-增加了水稻根尖伸長(zhǎng)區(qū)的Cd2+流通量,相比對(duì)照增加53.2%,過量NO_3~-處理的水稻,其根部、地上部及稻米中的Cd含量分別比對(duì)照高出8.0%、67.0%、93.0%,而缺NO_3~-顯著降低了Cd2+流通量及Cd在植株各部位的積累。進(jìn)一步研究表明,過量NO_3~-上調(diào)了根尖Fe轉(zhuǎn)運(yùn)體Os IRT1基因的表達(dá),致使水稻根部和地上部Fe含量分別增加13.5%和59.9%。因此,過量的NO_3~-增加了稻米Cd毒害風(fēng)險(xiǎn),建議在Cd污染稻區(qū)避免大量施用NO_3~-肥。3.過量NH_4~+通過調(diào)節(jié)根部金屬螯合肽含量及抗氧化物酶活性減輕了水稻Cd毒害。在水培條件下,采用不同濃度的NH_4~+肥處理3周大的水稻品種日本晴,結(jié)果發(fā)現(xiàn),Cd脅迫下過量NH_4~+顯著增加了水稻株高、葉綠素a含量、葉綠素b含量、光合速率、地上部氮含量,增幅分別為4.7%、17.8%、27.1%、28.0%、7.9%,而缺NH_4~+顯著降低了這些指標(biāo)。進(jìn)一步研究表明,過量NH_4~+處理下,水稻根部硫含量和硫積累量分別增加了17.8%和17.4%,根部金屬螯合肽含量增加了6.8%,水稻Cd毒害減輕。另外,過量NH_4~+顯著降低了水稻根部和地上部丙二醛含量、根部過氧化氫含量,其降幅分別為13.4%、13.2%、23.9%,缺NH_4~+顯著增加了脅迫程度。同時(shí),過量NH_4~+顯著上調(diào)了根部Os MT-1基因、地上部Os LCD基因的表達(dá)。過量NH_4~+增加了根部和地上部過氧化物酶(POD)和地上部抗壞血酸氧化酶(APX)活性,增幅分別為31.3%、35.3%、12.6%。因此,過量NH_4~+提高了水稻POD和APX活性,減輕了水稻Cd毒害。4.過量NH_4~+促進(jìn)了Cd向水稻地上部的轉(zhuǎn)運(yùn)。過量NH_4~+處理的水稻地上部/根部Cd含量比增加了14.5%,而缺NH_4~+顯著降低了這一轉(zhuǎn)運(yùn)比率。另外,過量NH_4~+顯著下調(diào)了水稻根部Os HMA3基因表達(dá),減少了螯合肽Cd向液泡中的固定,因此,NH_4~+通過下調(diào)根部Os HMA3基因表達(dá)增加了水稻植株Cd向地上部的轉(zhuǎn)運(yùn)。5.酰胺態(tài)氮(Urea)能通過上調(diào)水稻Cd吸收和轉(zhuǎn)運(yùn)基因的表達(dá)增加Cd的積累。采用不同濃度的Urea處理水稻,過量Urea處理下水稻根部硝態(tài)氮、硝銨比均增加,同時(shí)也上調(diào)了根部Os Nramp1、Os Nramp5和Os HMA2基因的表達(dá),增加了水稻根部和地上部Cd的含量,而缺Urea降低了這些指標(biāo)。氮肥形態(tài)與用量對(duì)水稻Cd吸收和毒害的影響及其調(diào)控機(jī)制研究,對(duì)水稻生產(chǎn)與稻米安全具有重要的理論和實(shí)際意義。本研究以水稻最常用的3種氮肥形態(tài)和用量,研究水稻Cd吸收、積累及毒害的生理及分子機(jī)制,為水稻Cd危害調(diào)控技術(shù)提供理論支持,同時(shí)也為Cd污染稻區(qū)氮肥管理提供參考。
[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.
【學(xué)位授予單位】：中國(guó)農(nóng)業(yè)科學(xué)院
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：S511

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