This study aimed to further understand the toxicity of high concentrations of nitrogen dioxide (NO₂) to plants, especially to plant photosynthesis. Tobacco plants in the six-leaf stage were exposed to 16.0 μL L⁻¹ NO₂ to determine the activities of photosystem II (PSII) and photosystem I (PSI) reaction centers, the blocking site of PSII electron transport, the degree of membrane peroxidation and the relative expression of PsbA, PsbO and PsaA genes in the third fully expanded leaves by using gas exchange and chlorophyll fluorescence techniques, biochemical and RT-PCR analysis. The results showed that 16.0 μL L⁻¹ NO₂ caused necrotic lesions to form on leaves and significantly increased the generation rate of superoxide anions (O₂^-) and the content of peroxynitrite (ONOO⁻) in leaves of tobacco seedling, leading to damage to cell membrane, chlorophyll content and net photosynthetic rate reduction, and photosynthetic apparatus destruction. Fumigation with 16.0 μL L⁻¹ NO₂ decreased the activity of PSII reaction center and oxygen evolution complex, and the relative expression of PabA in leaves of tobacco seedlings to inhibit the electron transport from the donor side to the receptor side of PSII, especially blocking the electron transport from Q_A to Q_B on the receptor side. The activity of the PSI reaction center and the relative expression of PsaA decreased, weakening the ability to accept electrons and inhibiting the electron transfer from PSII to PSI, which further increased the damage of PSII of tobacco seedling leaves caused by 16.0 μL L⁻¹ NO₂. Therefore, 16.0 μL L⁻¹ NO₂ leaded to the accumulation of O₂^- and ONOO⁻, which damaged the cell membrane and thylakoid membrane, inhibit the electron transport, and destroyed the photosynthetic apparatus in leaves of tobacco seedlings. The results from this study emphasized the importance of reducing the NO₂ concentration in the atmosphere.

本研究旨在进一步了解高浓度二氧化氮（NO ₂ ）对植物尤其是植物光合作用的毒性。将六叶期烟草植株置于16.0 μL L ^-1 NO ₂中，测定光系统II（PSII）和光系统I（PSI）反应中心的活性、PSII电子传递的阻断位点、膜过氧化程度利用气体交换和叶绿素荧光技术、生化和RT-PCR分析，检测第三完全展开叶中PsbA 、 PsbO和PsaA基因的相对表达量。结果表明，16.0 μL L ^-1 NO ₂使烟苗叶片形成坏死病斑，并显着增加烟苗叶片中超氧阴离子（O ₂ ^- ）的生成率和过氧亚硝酸盐（ONOO ^- ）的含量，造成危害。使细胞膜、叶绿素含量和净光合速​​率降低，并破坏光合器官。 16.0 μL L ^-1 NO ₂熏蒸降低烟苗PSII反应中心和析氧复合物的活性以及PabA的相对表达量，抑制PSII供体侧向受体侧的电子传递，尤其是阻断电子从受体一侧的 Q _A传输到 Q _B 。 PSI反应中心活性和PsaA相对表达量下降，接受电子能力减弱，抑制PSII向PSI的电子传递，进一步加重16.0 μL L ^-1 NO对烟苗叶片PSII的损伤₂ .因此，16.0 μL L ^-1 NO ₂导致O ₂ ^-和ONOO ^-积累，损害细胞膜和类囊体膜，抑制电子传递，破坏烟苗叶片的光合机构。这项研究的结果强调了降低大气中 NO ₂浓度的重要性。