【作者】 杨建立；

【导师】 郑绍建；

【作者基本信息】 浙江大学 ， 植物营养学， 2004， 硕士

【摘要】 铝毒是限制酸性土壤作物生长的主要因素。我国酸性土壤遍及南方15个省区，总面积为2030万hm~2，约占全国土地总面积的21％。选育和通过生物工程手段创建适合酸性铝毒土壤上生长的植物是一种经济有效的手段。本文对不同植物(包括荞麦、黑麦、小黑麦和小麦)耐铝的基因性差异进行了筛选，在已有的报道的基础上进一步对养麦耐铝机理做了深入的研究，并研究了蛋白合成抑制剂对铝诱导的荞麦分泌有机酸的影响和铝对荞麦根系和子叶蛋白组分的影响。结果摘要如下： 不同植物种类和同一植物种类不同品种的耐铝能力存在明显的基因型差异。就物种而言，在本研究中耐铝能力黑麦最强，依次为养麦、小照麦和小麦；就品种而言，小黑麦对铝胁迫所表现出来的基因型差异最大，表明六倍体小黑麦与其他作物相比在耐铝性上遗传变异更大。显著的基因型差异为培育适合酸性土壤生长的杂交品种提供了保障。根尖铝排斥机理在小黑麦耐铝性上起重要作用。本研究所得到的植物材料有助于对植物铝毒和耐性机理的深入研究。 首次报道了荞麦在耐铝性上存在着极大的基因型差异。并且其耐铝性与生长地域的土壤类型和土壤pH间有显著的相关性，表明荞麦耐铝除了己有报道的机理外可能还存在其它的山于民期适应酸J性铝毒土壤而形成的机理。进一步研究发现，铝诱导有机酸的分泌和有机酸对铝的内部鳌合机理都无法解释荞麦耐铝的墓因型差异。而从抗铝荞麦品种(收集自我国南方酸性土壤上)根系的Al和P含量远远高于铝敏感尸!种(收集自我国西北方石灰性土壤上)根系中的Al和P含量，我们认为省长与酸性土壤的荞麦品;种由于长期进化而存在着一种既能解除酸性土壤铝毒又能缓减缺磷这两种生长限制因子的机理存在。 铝诱导植物分泌有机酸而提高植物耐铝性被普遍报道。这过程是通过细胞膜上的阴离子通道蛋白实现的。但是关于这些通道蛋白是原先就存在于细胞膜上，还是铝诱导了这些蛋白的合成而导致了有机酸的分泌还不清楚。我们的结果表明一种)’‘普蛋白合成抑制剂环己酞亚胺(cycloheximide)对铝诱导的有机酸从荞麦根系中的分泌不产生影响。说明阴离子通道蛋白是原来就存在于细胞膜上，铝处理只是激活了这些蛋白而使有机酸分泌的。更多还原

【Abstract】 Aluminum toxicity is one of the major factors limiting crop production in acid soils worldwide. In China, 21% of the total cultivated land is acidic, extending over 15 provinces in southern China. Selection and breeding of crops offers an alternative to lime application in acid soils, esp. where lime application is not economically feasible. At present, genotypic differences among plant species in response to Al stress were screened. The underlying mechanisms contributing to genotypic difference among buckwheat cultivars and the effect of cycloheximide. a broad protein synthesis inhibitor, on Al-induced oxalate efflux from buckwheat roots were investigated. In addition, preliminary experiment was conducted in order to investigate the effect of Al stress on root and leaf proteins. The results were summarized as followings.The genotypic differences among plant species or cultivars within the same species were substantial. The ability to resist Al stress is in the increasing order of wheat, triticale, buckwheat, and rye. The greatest genotypic variation of triticale in response to Al stress implys that hexaploid triticale possessed more genetic variation in their resistance to Al stress than other species. The marked genotypic differences make it possible to develop hybrids suitable for acid soils. In addition, Al exclusion from root tips may play a pivotal role in Al resistance in triticale. Using the plant materials with contrast Al tolerance as found in this study will help to clarify mechanisms of Al phytotoxicity and resistance in plants.Here, we demonstrated that there were considerable differences in Al resistances among the cultivars of buckwheat and found an extreme sensitive cultivar (Shanxi). Furthermore, Al resistance in this species correlated closely with growth inhabits of origin, indicating that adapted mechanisms leading to high Al resistance had been evolved in this species. Oxalic acid secretion from roots is considered to be an important mechanism for aluminum (Al) resistance in buckwheat. However, no correlation was found between Al-induced oxalic acid secretion and Al-induced inhibition of root elongation. The two cultivars showing the greatest difference in resistance were Shanxi (Al-sensitive) and Jiangxi (Al-resistant) and these were compared in more detailed studies. The dependence of oxalic acid secretion on external Al concentration and the time-course for secretion were similar in both cultivars. Furthermore the variation in Al-induced oxalic acid efflux along the root was similar showing a 10-fold greater from the apical 0-5 mm region than from the 5-10 mm region. These results suggest that both Shanxi and Jiangxi possess an equal capacity for Al-dependent oxalic acid secretion and that the variation in Al resistance among different cultivars cannot be explained by this mechanism. However after longer treatments in Al (10 days) the concentration of P and Al in the roots of the Al-resistant cultivar Jiangxi were significantly higher than those in Shanxi. These results suggest that while Al-dependent oxalic acid secretion might contribute to the overall high resistance to Al stress of buckwheat this response cannot explain the variation in tolerance between cultivars. We present evidence suggesting the greater Al resistance of Jiangxi is related to the immobilization and detoxification of Al by P in the root tissues.Organic acid secretion has been shown to play a central role in detoxifying aluminum both internal and external by forming chelating compounds. It was demonstrated that oxalate secretion plays a key role in the tolerant mechanism to aluminum stress in buckwheat, and was presumed be secreted through anion channels located on the plasma membrane. However, the question remains equivocal whether these channels are preexist in the plasma membrane or induced do novo synthesis by Al stress. Our results indicated that cycloheximide does not affect the secretion ofoxalate in buckwheat in response to Al stress, indicating that the activation of channels rather than de novo syn更多还原