干旱胁迫下黄土高原4种乡土禾草抗氧化特性

Abstract

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.