毛竹幼苗抗氧化酶和AsA-GSH循环对高温干旱及协同胁迫的响应

Responses of anti-oxidant enzymes and the ascorbate-glutathione cycle to heat, drought, and synergistic stress in Phyllostachys edulis seedlings

为了探讨毛竹Phyllostachys edulis对高温干旱及协同胁迫的响应,采用人工模拟干旱(对照、轻度、中度和重度干旱),高温(对照25℃和高温40℃)及协同胁迫处理毛竹3年生盆栽苗,分别测定叶片活性氧(ROS),丙二醛(MDA),抗坏血酸(As A)和谷胱甘肽(GSH)质量摩尔浓度,同时测定抗氧化防御酶和抗坏血酸-谷胱甘肽(As AGSH)循环酶活性的变化。结果表明:干旱胁迫下,毛竹叶片超氧阴离子(O2·-)和过氧化氢(H2O2)质量摩尔浓度显著增加(P<0.05),抗氧化酶活性及ρGSH/ρGSSG(GSSG为氧化型谷胱甘肽)比值均随干旱处理程度的增加而升高,其中超氧化物歧化酶(SOD),过氧化物酶(POD)活性和ρGSH/ρGSSG在中度干旱胁迫时较对照分别增加了1.7倍、1.7倍和0.6倍(P<0.01)。高温胁迫下,MDA较对照增加1.4倍(P<0.01);SOD,POD,过氧化氢酶(CAT)活性和ρAs A/ρDHA(DHA为二十二碳六烯酸)均极显著升高(P<0.01)。协同胁迫下,ROS进一步增加,膜脂过氧化程度增强,同时CAT活性的稳定性最强,活性随协同胁迫程度的增加稳步增加,ρAs A/ρDHA降低,而ρGSH/ρGSSG值变化不大,GSH循环对抵抗协同胁迫比As A循环表现出更强的耐性。在高温干旱及协同胁迫下,毛竹幼苗可以通过调节抗氧化酶系统和非酶系统As A-GSH循环协同作用来清除氧化物质,提高抗旱胁迫能力。

To study the physiological responses of 3-year-old Phyllostachys edulis seedlings to drought stress,heat stress,and synergistic stress,a pot experiment was conducted.Changes of reactive oxygen species(ROS),malondialdehyde(MDA),ascorbic acid,and glutathione concentration,as well as changes in enzyme activity of anti-oxidative enzymes and ascorbate-glutathione(AsA-GSH)cycle in the leaves of Ph.edulis were determined using an artificial simulation method by a spectrophotometer with different levels of drought stress(control check(70.0%-80.0%of field water-holding capacity),light stress(60.0%-70.0%FC),medium stress(40.0%-50.0%FC),and heavy stress(20.0%-30.0%FC)),heat stress(25℃and 40℃),and synergistic stress.Results showed that the contents of superoxide anion(O2·-)and hydrogen peroxide(H2O2)in leaves of Ph.edulis increased(P<0.05)compared to ck with drought stress.Anti-oxidant enzyme activities and theρGSH/ρGSSG ratio increased(P<0.05)compared to ck with an increase in the degree of drought stress.With moderate drought stress,compared to ck,highly significant differences(P<0.01)were found for activities of superoxide dismutase(SOD)(1.7 times higher),peroxidase(POD)(1.7 times higher),and the ratio ofρGSH/ρGSSG(0.6 times higher).Compared to ck,MDA increases(1.4 times)were highly significant(P<0.01),and increases in the activity of SOD,POD,and catalase(CAT),along with the ratioρAsA/ρDHA were highly significant(P<0.01)with heat stress.After synergistic stress,compared to ck,ROS increased(P<0.01),and the degree of membrane lipid peroxidation was enhanced(P<0.01);meanwhile,the stability of CAT activity was strongest(P<0.01)increasing steadily compared to ck with an increase in synergism.Also,theρAsA/ρDHA ratio showed a downward trend;whereas,theρGSH/ρGSSG ratio was not significant.Thus,the GSH cycle showed stronger resistance to synergistic stress than the AsA cycle suggesting that Ph.edulis seedlings could protect themselves effectively from oxidative damage with a degree of heat,drought,and synergistic stress.