腐植酸浸种对低温胁迫下玉米幼苗抗氧化系统的影响

Abstract

低温冷害是导致黑龙江省玉米产量不稳、品质不高的重要农业气象灾害，而关于低温胁迫下玉米抗氧化应激能力和程度的研究较少。采用清水为对照（CK），以腐植酸质量浓度为0.2%、0.4%、0.8%、1.2%、1.6%和2.0%浸种，研究了昼夜温度为15℃/8℃低温胁迫48 h下玉米幼苗的代表性抗氧化酶活性、抗坏血酸-谷胱甘肽（AsA-GSH）循环、系统抗性及碳氮代谢的变化，以明确腐植酸对玉米的耐低温胁迫响应机制及适宜的浸种浓度。结果表明：低温胁迫条件下腐植酸浸种主要受过氧化氢（H₂O₂）积累诱导，随着浸种浓度的增加，大多数抗氧化酶和系统抗性酶活性、AsA-GSH循环、碳氮代谢主要物质含量、根系活力和鲜重均呈单峰曲线分布，其中0.8%-2.0%浓度处理的叶片和根系可溶性蛋白含量分别显著增加了23.3%-34.9%和31.9%-89.6%；1.6%浓度处理的叶片和根系苯丙氨酸解氨酶活性分别显著增加了16.8%和38.8%，多酚氧化酶活性分别增加了27.7%和13.4%，抗坏血酸含量分别显著增加了62.6%和55.3%，脱氢抗坏血酸含量分别显著增加了31.9%和66.4%；0.8%浓度处理的叶片和根系过氧化氢酶活性分别显著增加了66.4%和108.1%。因此，腐植酸浸种处理的叶片H₂O₂含量较对照显著降低了18.7%-37.6%，根系H₂O₂含量显著降低了27.5%-49.7%。0.4%和0.8%浓度处理的根系鲜重较对照分别显著增加了85.2%和105.3%，单株鲜重分别显著增加了31.9%和40.8%。腐植酸0.4%-0.8%处理增强了AsA为核心的AsA-GSH循环系统的运转活性和系统抗性，提高了玉米幼苗的抗氧化应激能力，获得最大的根系活力和植株鲜重，是水培条件下较为适宜的浸种浓度。;Chilling damage in Heilongjiang Province is an important agricultural meteorological disaster that leads to unstable maize yield and low quality in this region. However, there are few studies on the ability and degree of antioxidant stress in maize under low-temperature stress. Mass concentration of humic acid were 0.2%, 0.4%, 0.8%, 1.2%, 1.6% and 2.0%, and water as the control, the changes of activities of representative antioxidant enzymes, ascorbic acid-glutathione (AsA-GSH) cycle, systemic resistance and carbon-nitrogen metabolism of maize seedlings under low-temperature stress of day and night for 48 h at 15℃/8℃ were studied to illustrate the tolerance mechanism of humic acid for low-temperature stress and the appropriate concentration of soaking seed. The results showed that soaking seed with humic acid was mainly induced by H₂O₂ accumulation under low temperature stress. With the increase of seed soaking concentration, most of the activity of antioxidant enzymes and system resistance enzymes, the AsA-GSH cycle and main substance content of carbon and nitrogen metabolism, root activity and fresh weight showed unimodal curve distribution. The soluble protein content of leaves and roots increased by 23.3%-34.9% and 31.9%-89.6% at the concentration of 0.8%-2.0%, respectively. The activity of phenylalanine ammonia-lyase increased by 16.8% and 38.8%, the activity of polyphenol oxidase increased by 27.7% and 13.4%, the content of ascorbic acid increased by 62.6% and 55.3%, and the content of dehydroascorbic acid increased by 31.9% and 66.4% in leaves and roots at the concentration of 1.6%, respectively. The activity of hydrogen peroxide in leaves and roots increased by 66.4% and 108.1% at the concentration of 0.8%. Therefore, H₂O₂ content in leaves and roots after soaking seed significantly reduced by 18.7%-37.6% and 27.5%-49.7% compared with the CK, respectively. The fresh root weight increased significantly by 85.2% and 105.3%, and the fresh weight of single plant increased significantly by 31.9% and 40.8% at the concentration of 0.4% and 0.8% compared with the control, respectively. In this study, the treatment at the concentration of 0.4%-0.8% enhanced the operation activity and systemic resistance of the AsA-GSH circle system with AsA as the core, improved the antioxidant stress ability of maize seedlings, and obtained the maximum root activity and fresh weight of plant, which were a relatively appropriate seed soaking concentration under hydroponic condition.