近地层臭氧对小麦抗氧化酶活性变化动态的影响

摘要:利用开顶式气室（TOCs）模拟了地表O3浓度升高的大田试验条件，测定了小麦各生长期(返青期、拔节期、孕穗期、抽穗期、灌浆期、成熟期)叶片抗氧化酶的活性。通过两年的重复试验，得到相似结果。试验表明,过氧化氢酶（CAT）和过氧化物酶（POD）活性在小麦的生长进程中，先升高后降低。O3浓度升高使CAT酶和POD酶活性的峰值期提前，POD酶峰值期明显提前所需的O3浓度比CAT酶高，O3诱导小麦生长前期的CAT、POD酶活性升高，后期则起抑制作用。POD酶对低浓度O3的胁迫响应时间较晚。当O3浓度提高到150 nL?L-1时，超氧化物歧化酶（SOD）活性随小麦生长期的变化，由原来的双峰曲线变为单峰曲线，高浓度O3使SOD酶活性在抽穗期后持续显著降低。O3不明显改变抗坏血酸过氧化物酶（APX）对胁迫的响应时间，但一定浓度范围内O3能诱导APX酶活性升高。不同浓度的O3对SOD酶和APX酶的作用效应和强度显著不同, CAT酶和POD酶对O3比较敏感。 因此，近地层O3浓度增加，改变了CAT、POD和SOD酶活性变化的时序特征，抗氧化酶对O3胁迫的响应特征取决于小麦的生育期、O3的浓度和薰气时间。

Concentration of O3 at the atmospheric surface affects the changes characters of antioxidant enzyme activities in Triticum aestivum

Using ozone treatments in OTCs (open top chambers), the effect of increase atmospheric surface level ozone (O₃) contents on antioxidant enzymes activities of winter wheat leaves(Triticum aestivum)was investigated, in the growing/development (G/D) periods including reviving, jointing, booting, heading, filing and mature stages. Two experiments were performed in two years by doing each experiment in one year,using six OTCs in each. The chambers were equivalent, but two were fed with air while the other four with ozone at different concentration, in that two chambers with 100nL/L and the other two with 150nL/L.Winter wheat were grown to all life stage in OTCs. From reviving to mature stages, the plants were treated for 8 h (8:00-16:00) in every sunny day with different dose of O₃, respectively. The activities of winter wheat leaves (the second and the 5th from the top). Catalase(CAT), peroxidase (POD), superoxide dismutase (SOD) and ascorbate peroxidase (APX) were measured. Antioxidant enzymes of each treatment was assayed in triplicate. The data were initially compared by analysis of variance and differences between means were detected using the Duncans Multiple Range Tests. Values of P<0.05 indicated significance. Quite similar results were obtained during two years' experiments, suggesting that as a G/D stage is progressing, the activities of leaves catalase (CAT) and peroxidase (POD) increased firstly but consequently declined. Under the increased O₃ stress, CAT and POD activities raised and their peak values appeared earlier, but POD needed higher O₃ concentration than CAT's, The activeness of CAT and POD is induced in the later G/D period. Subjected to low concentration of O₃, POD activity was found to remain unaffected in longer time compared to CAT. When the O₃ concentration was increased to 150 nL/L, the relationship of superoxide dismutase (SOD) activities against wheat growth stages was altered from double hump to single hump style. SOD activity was found to be obviously decreased in the advance G/D period under higher O₃ stress. No obvious influence was found for the time response of ascorbate peroxidase caused by O₃ stress, but in a certainly range, while O₃ concentration could induce APX activity. The effects and influenced strength are significantly different between superoxide dismutase and ascorbate peroxidase against O₃ doses. CAT and POD are more sensitive to O₃ than SOD and APX. Taking together,the elevated O₃ concentration in atmospheric surface layer, impinges on the time series features of CAT, POD and SOD. O₃ stresses could induce oxidative stress. Antioxidant enzymes activities were upregulated under low concentration and short time ozone fumigation. Otherwise, enhance O₃ irradiation and prolong fumigation time the activities of antioxidant enzymes were inhibited. The effects on antioxidant enzymes activities are relate to (G/D) periods of winter wheat, dose of O₃ and the exposure time. Various antioxidant enzymes have different O₃-sensitive, representing that the threshold of subjected to O₃, the responses time to O₃ stress and the variation scope of antioxidant enzymes activities are different.