铝胁迫诱导根系分泌异羟肟酸及其对玉米抵御铝毒害的作用

Al-Induced Hydroxamates Cyclic Secretion from Roots to Resist Al Toxicity in Maize

【目的】通过对铝诱导玉米根系分泌异羟肟酸的研究,为揭示玉米的耐铝机制提供理论依据。【方法】选用玉米品种郑单958和泰玉11号,采用水培方法,设置铝胁迫试验,测定它们在铝胁迫下根伸长量、根尖铝含量、根尖胼胝质含量、根系异羟肟酸的分泌量、异羟肟酸解铝毒的相关指标等,分析玉米的抗铝性、铝对根系分泌异羟肟酸的影响及异羟肟酸的解铝毒作用。【结果】与对照(不加铝)处理相比,10μmol·L^(-1)铝(Al Cl3)处理后郑单品种幼根伸长显著受阻而根尖铝含量和根尖胼胝质积累量显著增加。根伸长量降低了47.77%,根尖铝含量和根尖胼胝质含量分别增加了226.64%和60.74%。相反,铝处理对泰玉品种幼根伸长、根尖胼胝质积累的影响不显著。虽然20μmol·L^(-1)铝(AlCl_3)处理44 h后泰玉品种根系柠檬酸分泌量比对照(不加铝)处理显著增加了41.28%,但处理24 h内2个玉米品种根系柠檬酸分泌量与对照(不加铝)处理的差异不显著,即24 h内铝不能诱导玉米根系分泌柠檬酸。而铝处理24 h后,铝能诱导泰玉根系分泌异羟肟酸(丁布和门布),且异羟肟酸的分泌量随着铝浓度(10、15和20μmol·L^(-1))的增加和处理时间(3、6、9、12和24 h)的延长而显著增加,但铝(10、15和20μmol·L^(-1))不能诱导郑单品种根系分泌异羟肟酸。与光照条件相比,在黑暗条件下20μmol·L^(-1)铝(AlCl_3)诱导泰玉品种异羟肟酸的分泌量显著增加而根伸长也随之显著改善,丁布和门布的分泌量分别增加了40.81%和72.02%,根伸长量增加了33.15%。与单独20μmol·L^(-1)铝(AlCl_3)处理相比,铝溶液中添加丁布(3 mg·L^(-1))和门布(3 mg·L^(-1))后玉米初生根伸长量显著增加而根尖铝含量显著降低。添加丁布和门布后,郑单品种根伸长量分别增加了14.16%和13.85%,泰玉品种分别增加了16.16%和11.33%;郑单品种根尖铝含量分别降低了39.94%和43.54%,泰玉品种分别降低了39.92%和42.10%。另一方面,20μmol·L^(-1)铝(AlCl_3)处理显著增加泰玉品种根和叶片中的异羟肟酸含量。然而,铝胁迫下郑单叶片中的异羟肟酸含量显著降低。【结论】玉米对铝的抗性与异羟肟酸的分泌有关,铝诱导玉米根系分泌异羟肟酸是玉米抵御铝毒害的一种有效机制,而植株叶片中的异羟肟酸含量可能与异羟肟酸的分泌有关。

【Objective】Al-induced secretion of Hydroxamates Cyclic from roots was investigated and we provided a theoretical basis for revealing the mechanism responsible for Al-resistance in Zea Mays L..【Method】The experiment was conduced using a Zhengdan 958 variety and a Taiyu No.11 variety with Al treatment by hydroponics. The Al-resistance and the effect of Al on the secretion of Hydroxamates Cyclic from roots and Hydroxamates Cyclic ameliorated Al toxicity were studied by measuring the root elongation, Al content, callose content, Hydroxamates Cyclic secretion, and relevant indicators of Hydroxamates Cyclic-ameliorated Al toxicity among these two varieties.【Result】With comparison to the control treatment（without AlCl_3）, root elongation was inhibited significantly, while Al and callose content of root tips increased significantly in Zhengdan with 10 μmol·L^（-1） AlCl_3 treatment after 24 h. When root elongation was reduced by 47.77%, Al and callose content of root tips increased by 226.64% and 60.74%. On the contrary, there were no significant effects on the root elongation and callose content of root tips in Taiyu. Although Citrate secretion increased significantly by 41.28% from roots in Taiyu with 20 μmol·L^（-1） AlCl_3 treatment after 44 h, Citrate secretion did not increase significantly from roots in Taiyu and Zhengdan with AlCl_3 treatment during 24 h with comparison to control treatment（without AlCl_3）, meaning Al cannot induce Citrate secretion from roots in maize during 24 h. Al-induced Hydroxamates Cyclic（DIMBOA and MBOA） secretion from roots of Taiyu, the amount of Hydroxamates Cyclic secretion increased significantly with the increasing AlCl_3 concentration（10, 15 and 20 μmol·L^（-1）） and the duration of AlCl_3 treatment（3, 6, 9, 12 and 24 h）, but Hydroxamates Cyclic secretion did not increased significantly from roots in Zhengdan with AlCl_3（10, 15 and 20 μmol·L^（-1））. And dark condition can significantly improve the secretion of Hydroxamates Cyclic in Taiyu and effectively reduce Al-induced（20 μmol·L^（-1） AlCl_3） inhibition of root elongation compared to the light condition. DIMBOA and MBOA secretions increased by 40.81% and 72.02%, and root elongation increased by 33.15%. Compared to the sole Al（20 μmol·L^（-1） AlCl_3） treatment, addition of DIMBOA（3 mg·L^（-1）） and MBOA（3 mg·L^（-1）） to Al solution can significantly increase root elongation, reducing Al content of root tips in maize. With the addition of DIMBOA and MBOA to Al solution, root elongation of Zhengdan increased by 14.16% and 13.85%, and Taiyu increased by 16.16% and 11.33%; Al content of root tips of Zhengdan was decreased by 39.94% and 43.54%, Taiyu decreased by 39.92% and 42.10%. On the other hand, 20 μmol·L^（-1） AlCl_3 treatment increased significantly Hydroxamates Cyclic content of roots and leaves in Taiyu. However, Al treatment decreased significantly Hydroxamates Cyclic content of the leaves in Zhengdan.【Conclusion】These results suggested that Al-resistance bears on Hydroxamates Cyclic secretion. Al-induced secretion of Hydroxamates Cyclic from roots may be an effective mechanism for maize under Al-stress, Hydroxamates Cyclic content of the leaves may be involved in the secretion in the maize.