干旱胁迫下黄土高原4种乡土禾草抗氧化特性

采用盆栽实验,对干旱胁迫下黄土高原4种乡土禾草冰草、长芒草、无芒隐子草和白羊草叶片过氧化氢(H₂O₂)、丙二醛(MDA)含量、抗氧化酶超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、脱氢抗坏血酸还原酶(DHAR)、单脱氢抗坏血酸还原酶(MDHAR)、谷胱甘肽过氧化物酶(GPX)活性和非酶抗氧化物质还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)、类胡萝卜素(Car)含量进行了测定。 结果表明:随着干旱胁迫程度的加剧,4种乡土禾草叶片H₂O₂、MDA含量均呈增加趋势,这说明它们均遭受了干旱所造成的氧化胁迫,且干旱程度越大其遭受的氧化胁迫也越大。由于4种乡土禾草均为禾本科植物并生存于相同的生态环境中,它们在抗氧化特性上具有一定共性。在60%FC和45%FC干旱胁迫下,4种乡土禾草均可以通过增加抗氧化酶SOD、CAT、APX、GR、DHAR、MDHAR、GPX活性和非酶抗氧化物质AsA含量来抵御干旱所造成的氧化胁迫。由于种属差异,4种乡土禾草的抗氧化特性也存在差异。在60%FC和45%FC干旱胁迫下,冰草、无芒隐子草和白羊草还通过增加非酶抗氧化物质Car含量增强抗氧化能力,长芒草和白羊草则还可通过增加POD活性抵御干旱。在60%FC干旱胁迫下,冰草还可通过增加非酶抗氧化物质GSH含量提高其抗氧化性。采用隶属函数法对4种乡土草种抗氧化能力的综合评价表明,冰草的抗氧化能力最强,其次为无芒隐子草和白羊草,长芒草的抗氧化能力最差。

Antioxidant properties of four native grasses in Loess Plateau under drought stress

The grasses Agropyron cristatum, Stipa bungeana, Cleisto genessongorica, and Bothriochloa ischaemum are widely distributed on the Loess Plateau, and all are drought-resistant to varying degrees. However, little is known about the responses of their antioxidant systems to drought stress. The objective of this study was to investigate the antioxidant properties of four native grasses in response to drought stress, to provide a theoretical basis for selecting grasses suitable for vegetation/ecological restoration on the Loess Plateau. The treatments consisted of three levels of drought; 80, 60, and 45% of field capacity (FC) levels. These moisture levels were obtained by a weighing method using a pot experiment system. Leaf samples were taken from the four native grasses after 30 days of drought treatments. Assays were conducted on the leaf tissue to determine the activities of the following antioxidant enzymes:superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione peroxidase (GPX, EC 1.11.1.9). In addition, we determined the contents of hydrogen peroxide (H₂O₂), malondialdehyde (MDA), reduced glutathione (GSH), reduced ascorbic acid (AsA) and carotenoid (Car) in the leaves. The results showed that the MDA and H₂O₂ contents in the leaves of the four grasses increased with increasing levels of drought stress. These results suggested that all the grasses suffered oxidative damage under different levels of drought stress and that the oxidative damage became more serious with increasing levels of drought stress. According to their MDA and H₂O₂ contents, the magnitude of oxidative damage was greatest in S. bungeana, followed by B. ischaemum, then C. genessongorica, and then A. cristatum. The four grasses enhanced their antioxidant capacity by increasing activities of antioxidant enzymes and the contents of antioxidant substances under different levels of drought stress. The four grasses all belong to the Gramineae family and inhabit the same ecological environment. Therefore, they showed some similarities in their antioxidant responses to drought stress. At both 60% and 45% FC levels, all four grasses protected themselves against drought-induced oxidative damage by increasing the activities of SOD, CAT, APX, GR, DHAR, MDHAR, and GPX, and their AsA content. However, since the four grasses were all different species, there were also some differences in their antioxidant responses. At both 60% and 45% FC levels, A. cristatum, C. genessongorica, and B. ischaemum protected themselves by increasing their Car content, while S. bungeana and B. ischaemum protected themselves by increasing POD activity. At the 60% FC level, A. cristatum showed an increase in GSH content. The overall trend in antioxidant capacity for the four grasses was as follows:A. cristatum > C. genessongorica > B. ischaemum > S. bungeana, as determined by comprehensive evaluation using the subject function method. Above results suggested that A. cristatum is the most drought-resistant, followed by C. genessongorica and B. ischaemum, while S. bungeana is the least drought-resistant. Thus, A. cristatum, C. genessongorica, and B. ischaemum are suitable grasses for vegetation/ecological restoration on the Loess Plateau.