大气臭氧浓度升高对银杏叶片活性氧代谢及相关基因表达的影响

采用开顶式气室熏蒸法,设置自然条件下臭氧(O₃)浓度(对照,约40 nmol·mol^-1)、80、160及200 nmol·mol^-14个臭氧浓度,观测了不同浓度臭氧条件下银杏叶片可见伤害、活性氧生成量、抗氧化酶活性及相关基因表达变化情况,分析大气臭氧浓度升高对植物活性氧代谢的影响.结果表明: 160和200 nmol·mol^-1 O₃熏蒸明显伤害银杏叶片,80 nmol·mol^-1与对照无差异,无可见伤害.O₃处理20 d后,160和200 nmol·mol^-1条件下银杏叶片的超氧自由基(O₂^-·)产生速率显著高于80 nmol·mol^-1和对照,而80 nmol·mol^-1与对照无差异;O₃处理40 d后,160和200 nmol·mol^-1熏蒸下叶片过氧化氢(H₂O₂)含量显著高于80 nmol·mol^-1和对照,而过氧化氢酶(CAT)活性显著高于80 nmol·mol^-1和对照,各臭氧处理抗坏血酸过氧化物酶(APX)活性均低于对照.熏蒸40 d后,CAT、APX基因的转录表达持续加强;防御素(GbD)的表达强度则随着臭氧浓度的增加及熏蒸时间的延长而呈显著加强.高浓度臭氧胁迫可使银杏叶片活性氧生成量增加、抗氧化酶活性下降、相关基因表达水平上调,有明显可见叶片伤害.

Effects of elevated ozone concentrations on reactive oxygen metabolism and related gene expression in Ginkgo biloba leaves

By using the open top chambers (OTCs) fumigation method, this paper investigated the changes of foliar injury, level of reactive oxygen species (ROS), activities and gene expression of antioxidant enzymes in Ginkgo biloba leaves under different ozone (ambient ozone≈40, 80, 160, 200 nmol·mol^-1) concentrations, in order to study the effects of elevated ozone (O₃) concentrations on reactive metabolism. The results showed that the obvious foliar injuries were observed in 160 and 200 nmol·mol^-1 O₃ treatments, while no visible injury was observed in 80 nmol·mol^-1 O₃ and ambient O₃ treatments. After 20 d, a significant increase in O₂^-· generation rate was observed in G. biloba leaves exposed to 160, 200 nmol·mol^-1 O₃, compared with ambient ozone and 80 nmol·mol^-1 O₃, and there were no significant differences between ambient O₃ and 80 nmol·mol^-1 treatments. After 40 d, H₂O₂ content of G. biloba leaves in 160 and 200 nmol·mol^-1 O₃ was significantly higher than that in 80 nmol·mol^-1 and ambient ozone, respectively. The activities of catalase (CAT) in 160 and 200 nmol·mol^-1 treatments were also significantly higher than that in 80 nmol·mol^-1 and ambient O₃ treatments. The ascorbate peroxidase (APX) activity of leaves for each elevated O₃ treatment was lower than that of ambient ozone. The level of CAT and APX expression increased progressively after 40 d O₃ treatment. The expression intensity of GbD was conspicuously strengthened along with the increase of ozone concentration and fumigation time. Le-vel of reactive oxygen increased, activities of antioxidant enzyme decreased, level of gene expression down-regulated, and foliar visible injury was observed in leaves of G. biloba in elevated ozone stress.