铝(Al)是酸性土壤常见的金属污染物之一。为探明外源有机酸对铝胁迫下菊芋(Helianthus tuberosus)生理特征及根系DNA损伤的影响, 以耐铝品种徐州菊芋和铝敏感品种资阳菊芋为材料, 设置0、350和700 µmol∙L^-1铝处理, 同时分别施加0、30、60和90 µmol∙L^-1复合有机酸, 探究外源有机酸对铝胁迫下各时期(7、14和21天)菊芋生理响应和DNA损伤的影响。结果表明, 铝胁迫抑制菊芋根伸长与根系活力, 严重损害菊芋的光合机构与抗氧化系统, 随着铝浓度的增加, DNA拖尾程度升高, DNA受损加剧。而施加复合有机酸能有效缓解铝胁迫造成的损伤。施加60 µmol∙L^-1有机酸可增强抗氧化酶活性, 提高最大光化学效率并促进根尖有机酸分泌, 其中柠檬酸分泌量分别比对照高2倍(徐州菊芋)及0.75倍(资阳菊芋), 根尖铝含量降低, 根系活力增强, 徐州菊芋和资阳菊芋DNA尾距较单独铝处理组下降51.53%和35.10%, 显著缓解DNA拖尾现象, 较大程度修复了DNA断裂。综上, 铝胁迫对菊芋造成的损害严重且较难缓解, 60 µmol∙L^-1有机酸能增强低铝胁迫下菊芋生理响应, 降低DNA受损程度, 提高菊芋的抗逆性, 且在铝敏感品种资阳菊芋中缓解效果更好。该研究揭示了外源复合有机酸对铝胁迫下菊芋生理响应系统的调控作用, 可为菊芋等经济作物在南方酸铝地区的种植与生产提供理论依据。

Aluminum (Al) is one of the common metal contaminants in acidic soils. To reveal the effects of exogenous organic acids on the physiological characteristics and root DNA damage of Helianthus tuberosus under Al stress, we used Al resistant H. tuberosus cv. ‘Xuzhou’ and Al sensitive H. tuberosus cv. ‘Ziyang’ as materials. The effects of exogenous organic acids on the physiological responses and DNA damage of H. tuberosus at various periods (7, 14, and 21 d) under Al stress were investigated by setting 0, 350 and 700 µmol∙L^-1 Al concentration treatments and applying 0, 30, 60 and 90 µmol∙L^-1 compound organic acids, respectively. The results showed that Al stress inhibits root elongation and root activity, severely inhibited the photosynthetic and antioxidant systems of H. tuberosus, and the DNA damage in the root system increased with the increase of Al concentration. In contrast, the application of compound organic acid effectively alleviated Al stress. 60 µmol∙L^-1 compound organic acid improved the activity of the antioxidant system, maximum photochemical efficiency and organic acid secretion in root tips, secretion of citric acid was 2 times (H. tuberosus cv. ‘Xuzhou’) and 0.75 times (H. tuberosus cv. ‘Ziyang’) higher than the control, reduced root tip Al content and improved root activity. Besides, H. tuberosus cv. ‘Xuzhou’ and H. tuberosus cv. ‘Ziyang’ oliver tail moment decreased by 51.53% and 35.10%, and compound organic acid reduced the DNA trailing phenomenon and repaired DNA breaks to a greater extent. In conclusion, high concentration of Al causes serious damage to H. tuberosus, which is difficult to mitigate. 60 µmol∙L^-1 compound organic acid could enhance the H. tuberosus physiological responses under low Al stress, reduce DNA damage and thus improve the stress resistance. The alleviation effect was better in H. tuberosus cv. ‘Ziyang’. This study reveals the regulatory role of exogenous organic acids on the physiological responses of H. tuberosus under Al stress, and provides a theoretical basis for planting and production of H. tuberosus and production of other cash crops in the acid-aluminium areas of southern China.