Aluminum (Al) toxicity is a major limiting factor for plant growth on acid soils; plants have evolved different strategies to detoxify Al stress due to different growth environments. Elucidation of these strategies will help us generate crops with enhanced Al tolerance. Most land plants use secretion of organic acid anions, such as oxalate, citrate and malate in response to Al stress. However, little work has so far been reported on relationship between Al resistance and Al-induced exudation of hydroxamates cyclic from roots ofZea MaysL. varieties. In this study, fifty-six varieties of maize were used to study the relationship between hydroxamates cyclic and Al tolerance based on the root elongation, Al content, callose content and hydroxamates cyclic measured among these 56 varieties. Al could induce secretion of hydroxamates cyclic from roots of different maize varieties, and callose, Al content of root tips were also significantly increased after Al treatment. Furthermore, there was significantly positive correlation between the root elon-gation and Al-induced secretion of hydroxamates cyclic(rDIMBOA=0.4550**,rMBOA=0.6008**),whereas there was significantly negative correlation between the Al content and hydroxamates cyclic(rDIMBOA=-0.3542**,rMBOA=-0.4841**), and callose was also significantly positively related to hydroxamates cyclic (rDIMBOA=-0.3651**,rMBOA=-0.1351). Cluster analysis showed that Al-induced secretion of hydroxamates cyclic from 30 Al-tolerance varieties such as Taiyu No.11, Feiyu No.3 and so on were higher than those of 7 Al-sensitive varieties such as Zhengdan No.958, Beiyu No.2883 and so on. Our results suggested that the secretion of hydroxamates cyclic in roots could be a novel mechanism for some tolerance varieties to resist the toxicity of Al.%铝毒是植物在酸性土壤中生长的主要限制因子，由于生长环境的差异，植物进化出不同的策略来抵抗铝毒害。阐明这些机理，将有助于开发抗铝毒农作物新品种。大部分陆生植物利用根系分泌一些有机酸来对付铝毒害，但根系分泌的异羟肟酸类物质（丁布和门布等）与玉米的耐铝能力的关系尚未见报道。收集中国56个主栽玉米（Zea mays）品种，设置铝胁迫试验，测定它们在铝的胁迫下根系异羟肟酸的分泌量、根伸长量、根尖胼胝质的质量分数和铝质量分数，分析了根系分泌的异羟肟酸与玉米耐铝能力的相关性。结果表明，铝可诱导玉米根系分泌异羟肟酸；用铝处理后，玉米根伸长受阻，根尖铝质量分数和胼胝质质量分数增加。在铝的胁迫下，根相对伸长率与异羟肟酸分泌量呈极显著正相关（r 丁布=0.4550**，r 门布=0.6008**），而根尖铝质量分数与异羟肟酸分泌量呈极显著负相关（r丁布=-0.3542**，r门布=-0.4841**），根尖胼胝质质量分数与异羟肟酸分泌量也呈负相关（r 丁布=-0.3651**，r 门布=-0.1351）。并且，聚类分析表明耐铝型的30个玉米品种在铝胁迫下根系分泌异羟肟酸的能力显著高于铝敏感型的7个品种。这些研究结果表明，铝诱导的根系分泌异羟肟酸类物质可能是一些耐铝玉米品种抵御铝毒害的一种机制。
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