【作者】 蒋思丝；

【导师】 林咸永；

【作者基本信息】 浙江大学 ， 植物营养学， 2011， 硕士

【摘要】 据报道,pH低于5.5的酸性土壤约占全世界土地面积的30%和潜在可耕地面积的50%。在中国,酸性土壤遍布15个省区,总面积达203万平方公里,约占耕地面积的21%。酸性或生理酸性化肥的大量施用以及工业化过程造成的大范围酸性沉降加剧了土壤的酸化过程。研究表明,Al浓度低于10μmol/L就会严重抑制许多植物根系的生长以及对养分和水分的吸收,而一般酸性土壤溶液中Al的浓度为10-100μmol/L。因此,Al毒被认为是酸性土壤中限制作物生长最重要的障碍因子,严重影响酸性土壤的作物生产。虽然国内外学者针对植物铝毒胁迫及其耐性机理已开展了大量研究,但迄今为止植物适应铝胁迫的生理生化及分子机制仍不完全清楚。近年来已有一些证据表明抗坏血酸(AsA)作为一种主要的抗氧化剂在植物对铝毒胁迫的响应中起着非常重要作用,但是对铝影响植物体内AsA的机理以及外源AsA对铝毒胁迫的缓解效应及其机制等问题尚不清楚。因此,本文以前期筛选的一对耐铝性差异明显的小麦基因型鉴-864(耐性)和扬麦5号(敏感)为材料,通过水培试验研究铝对不同小麦基因型AsA代谢的影响、外源AsA或者AsA合成前体对铝毒的缓解效应及其机理,以期更加深入地揭示铝对植物的毒害及植物耐铝性机理。取得的主要研究结果如下：1、铝对不同小麦基因型根尖AsA含量的影响及其机理以2个不同耐铝性的小麦基因型为材料,采用水培试验的方法,研究铝对小麦体内抗坏血酸代谢的影响。结果表明,在0,10,30,50μmol/L AlCl3胁迫下处理24 h,鉴-864和扬麦5号根系伸长受抑制程度随着铝处理浓度的提高而加剧。在30μmol/L AlCl3胁迫下,2个基因型的相对根伸长率差异最大,鉴-864的相对根伸长率为52%,而扬麦5号仅为28%。由此可见,鉴-864是对铝毒耐性较强,而扬麦5号对铝毒较为敏感。此外,小麦根尖铝含量和MDA(脂质过氧化指标)含量也均随铝处理浓度的提高而增加,且2个基因型也在30μmol/L AlCl3胁迫下差异最大,表现为扬麦5号高于鉴-864；因此,在后面的研究中选择该浓度进行铝胁迫处理。铝胁迫处理显著提高2个小麦基因型根尖AsA含量、L-半乳糖酸-1,4-内脂脱氢酶(L-GalLDH)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)抗坏血酸过氧化物酶(APX)活性、AsA/DHA比值和抗坏血酸氧化酶(AAO)活性,且均表现为鉴-864高于扬麦5号。由此可见,铝诱导小麦体内AsA含量的提高与其促进AsA的合成和循环再生有关,鉴-864具有较强的合成、循环再生与降解的平衡能力,是其抵御铝诱导的氧化胁迫损伤的重要原因。2、外源AsA对铝胁迫下对小麦根尖AsA含量的影响及其机理以2个不同耐铝性的小麦基因型为材料,采用水培试验的方法,研究了外源AsA (0.5 mmol/L)预处理6h对小麦铝毒的缓解效应及其体内抗坏血酸代谢的影响。结果显示,AsA预处理可显著增加铝胁迫下2个小麦基因型的相对根长率,降低了根尖的铝含量,并显著增加2个小麦基因型根尖的AsA含量、AsA/DHA比值、L-GalLDH、MDHAR、DHAR、APX和AAO活性,且AsA含量、MDHAR、DHAR、APX和AAO活性在扬麦5号中的增加幅度大于鉴-864。可见,外源AsA主要通过促进AsA合成和循环再生能力而提高体内AsA含量,降低小麦根尖铝含量的吸收,缓解铝毒胁迫对小麦根系伸长的抑制作用。3、外源L-Gal对铝胁迫下对小麦根尖AsA含量的影响及其机理以2个不同耐铝性的小麦基因型为材料,采用水培试验的方法,研究了外源的AsA合成前体L-Gal (0.5 mmol/L)预处理6h对小麦铝毒的缓解效应及其体内抗坏血酸代谢的影响。结果显示,L-Gal预处理可显著增加了铝胁迫下2个小麦基因型的相对根长率,降低了根尖的铝含量,并显著增加2个小麦基因型根尖的AsA含量、AsA/DHA比值、L-GalLDH、MDHAR、DHAR、APX和AAO活性。可见,外源L-Gal可通过促进AsA合成和循环再生能力而提高小麦体内AsA含量,降低小麦根尖铝含量的吸收,缓解铝胁迫对小麦根系伸长的抑制作用。更多还原

【Abstract】 It was reported that soils with pH lower than 5.5 accounts for 30% of the world land, and 50% of the world arable land. In China, acidic soil distributed across 15 provinces, accounting for 203 square KM, and representing 21% of its arable land. Soil acidization arose from the application of acidic fertilizers and the industrialization process. Previous study indicated that when Al concentration is lower than 10μmol/L in soil, plant root growth is inhibited due to the problems in nutrients and water uptake. Normally, Al concentration varys between 10 to 100μmol/L in acidic soils. Therefore, Al toxicity is thought to be the most important inhibitor limiting crop productivity. Although there are many reports on the Al stress and its toxicity mechanism, little is known about the physiolical and molecular mechanism on the plant response againt Al toxicity.1. Mechanisms for the effects of Al on AsA content and As A metabolic enzymes activities between wheat genotypes differing in Al toleranceHydroponic experiments were carried out to study the effects of Al on AsA metabolism for two wheat genotypes varying in Al tolerance. The results indicated that the dose-dependent experiment of 24 h exposure to 0,10,30,50μmol/L AICl3 indicated that the root elongation of Jian-864 and Yangmai-5 was inhibited with the increasing Al concentrations. The greatest difference in relative root elongation (RRE) between the two genotypes was observed at the concentration of 30μmol/L AlCl3, with the RRE 52% of Jian-864 and only 28% of Yangmai-5. This shows Yangmai-5 was more sensitive to Al than Jiang-864. In addition, The Al content and monodehydroascorbate (MDA) content of Jian-864 and Yangmai-5 was promoted with the increasing Al concentrations. The greatest difference in Al content and MDA content between the two genotypes was observed at the concentration of 30μmol/L. So,30μmol/L AICl3 concentration is chosen for the following study.The dose-dependent experiment indicated that the AsA content, L-galactono-1,4-lactone dehydrogenase(L-GalLDH), monodehydroascorbate reductase(MDHAR), dehydroascorbate reductase(DHAR), ascorbate peroxidase(APX), AsA/DHA radio and ascorbate oxidase (AAO) activities in 0-10 mm root apex of two genotypes increased responding to the increasing Al concentration. However, Jian-864 is still superior to Yangmai-5. The results indicated that Al can increase the AsA content, induce the activity of enzymes related to metabolism and stimulate the antioxidant system response to Al stress. Meanwhile, AsA synthesis capability and metabolic enzyme activity closely associated with the differences in Al tolerance in different wheat genotypes.2. Mechanisms of the effects of Al on AsA content and AsA metabolic enzymes activities in different wheat genotypes with AsA applicationHydroponic experiments were carried out to study the effects of AsA catabatic mechanism and AsA metabolism for two wheat genotypes exposed, to 0.5 mmol/L AsA pretreatment for 6 h. The results indicated that the two wheat genotypes of relative root elongation (RRE) were increased significantly with AsA pretreatment, but Al content in roots is reduced. After AsA pretreatment, AsA content, AsA/DHA ratio, L-GalLDH, MDHAR DHAR, APX and AAO activity in wheat rose markedly. And the rate of increase of AsA content, MDHAR, DHAR, APX and AAO activity in Yangmai-5 was greater than the ones in the Jian-864. The results indicated that exogenous AsA can accelerate endogenous AsA, DHA and their metabolic enzymes involvingin synthesis, promote wheat root elongation and reduction of the aluminum absorption and relieve the Al inhibition in root apex.3. Mechanisms of the effects of Al on AsA content and AsA metabolic enzymes activities in different wheat genotypes with L-Gal applicationHydroponic experiments were carried out to study the effects of AsA catabatic mechanism and AsA metabolism for two wheat genotypes exposed to 0.5 mmol/L L-Gal pretreatment for 6 h. The results indicated that After L-Gal pretreatment, the RRE of two wheat genotypes were increased significantly, but Al content in roots is reduced. And AsA content, AsA/DHA ratio, L-GalLDH, MDHAR DHAR, APX and AAO activity in wheat were also promoted. The results indicated that exogenous L-Gal can promote the biosynthesis of endogenous AsA, DHA and their metabolic enzymes involved in synthesis, reduce the absorption of aluminum content and relieve the Al inhibition in root apex.更多还原