外源水杨酸对铝胁迫下菊芋根系分泌物的影响

Effects of exogenous SA on root exudates of Helianthus tuberosus under aluminum stress

关键词:  菊芋, 红壤地区, 铝胁迫, 水杨酸, 根系分泌物

Key words:   Helianthus tuberosus, red soil region, aluminum stress, salicylic acid(SA), root exudates

摘要:

为探究铝胁迫对菊芋根系分泌物的影响以及外源水杨酸(SA)的缓解作用,该文以耐铝型南京菊芋和铝敏感型资阳菊芋为试验材料,采用土培法,设置铝浓度500 μmol·L^-1,分析了不同浓度(10、100、1 000 μmol·L^-1)SA对铝胁迫下菊芋根系分泌物中有机酸、氨基酸以及根尖相关代谢酶活的影响。结果表明:(1)单铝胁迫会导致菊芋根系分泌物中柠檬酸、草酸、苹果酸浓度升高,且南京菊芋升高幅度大于资阳菊芋; 柠檬酸合酶和苹果酸脱氢酶在单铝胁迫下活性增强; 脯氨酸含量显著提升,总氨基酸浓度均显著减少。(2)外源SA加入后,南京菊芋根系分泌的柠檬酸、草酸、苹果酸浓度均得到不同程度提高,但经高浓度(1 000 μmol·L^-1)SA处理后资阳菊芋根系分泌草酸显著降低,且在各浓度SA处理下苹果酸浓度均无明显变化; 柠檬酸合酶活性出现不同程度的增强,但对南京菊芋根尖中苹果酸脱氢酶活性影响不大,且高浓度(1 000 μmol·L^-1)SA处理后显著降低了资阳菊芋根尖中苹果酸脱氢酶活性; 脯氨酸含量显著下降,从总氨基酸浓度变化来看,南京菊芋在高浓度(1 000 μmol·L^-1)SA、资阳菊芋在低浓度(10 μmol·L^-1)SA处理下得到最大缓解效果。因此,菊芋通过分泌有机酸应对铝毒侵害,外源SA可促进菊芋根系有机酸代谢速率,分泌更多的有机酸来缓解铝胁迫,这种缓解效果在耐铝性相对较强的南京菊芋中表现更好。

Abstract:

To investigate the effects of aluminum stress on root exudates of Helianthus tuberosus and the alleviating effect of exogenous salicylic acid(SA), we used aluminum-tolerant Nanjing H. tuberosus and aluminum-sensitive Ziyang H. tuberosus as experimental materials and set aluminum concentration of 500 μmol·L^-1 by soil culture method, and analyzed the effects of different concentrations(10, 100, 1 000 μmol·L^-1)of SA on the organic acids and amino acids in root exudates of H. tuberosus and related metabolic enzymes in root tips under aluminum stress. The results were as follows:(1)Concentrations of citric acid, oxalic acid and malic acid in the root exudates of H. tuberosus increased under single Al stress, and the increase was greater in Nanjing H. tuberosus than in Ziyang H. tuberosus; The activities of citrate synthase and malate dehydrogenase increased under single Al stress; The proline content increased significantly, and the concentration of total amino acids decreased significantly.(2)The concentrations of citric acid, oxalic acid and malic acid secreted by the root system ofNanjing H. tuberosus were increased to different degrees after the addition of exogenous SA, but the oxalic acid secreted by the root system of Ziyang H. tuberosus was significantly reduced after treatment with high concentration(1 000 μmol·L^-1)of SA, and there was no significant change in malic acid concentration under all concentrations of SA treatment; The citrate synthase activity appeared to be enhanced to different degrees, but it had little effect on malate dehydrogenase activity in the root tips of Nanjing H. tuberosus, and malate dehydrogenase activity in the root tips of Ziyang H. tuberosus was significantly reduced after treatment with high concentration(1 000 μmol·L^-1)of SA; The proline content decreased significantly, from terms of changes in total amino acid concentration, the maximum alleviating effect was obtained at high concentration(1 000 μmol·L^-1)SA for Nanjing H. tuberosus and at low concentration(10 μmol·L^-1)SA for Ziyang H. tuberosus. Therefore, H. tuberosus responds to aluminum toxicity by secreting organic acids, and exogenous SA can promote the rate of organic acid metabolism in the root system of H. tuberosus to secrete more organic acids to alleviate aluminum stress, and this alleviation effect is better in Nanjing H. tuberosus, which is relatively strong in aluminum tolerance.