Effects of Aureobasidium pullulans PA-2 on photosynthetic characteristics and reactive oxygen species accumulation of Chenopodium album L. leaves

<bold>Objective</bold> To explore the response characteristics of <italic>Chenopodium album</italic> leaves to the fermentation broth of <italic>Aureobasidium pullulans</italic> PA-2 strain and provide a theoretical basis for the control of <italic>C</italic>. <italic>album</italic> by PA-2. <bold>Method</bold> Taking <italic>C</italic>. <italic>album</italic> as the research object，pot experiment was conducted to measure and analyze the photosynthetic characteristics and reactive oxygen species（ROS）accumulation of <italic>C</italic>. <italic>album</italic> leaves after spraying strain PA-2 fermentation broth（treatment）and sterile water（control）. <bold>Result</bold> The results showed that，compared with control，the chlorophyll content of <italic>C</italic>. <italic>album</italic> leaves in the treatment group decreased significantly，and net photosynthetic rate（<italic>P</italic>_n），transpiration rate（<italic>T</italic>_r）and stomatal conductance（<italic>G</italic>_s）showed an overall downward trend after the treatment of strain PA-2，while the intercellular CO₂ concentration（<italic>C</italic>_i）increased significantly，indicating that photosynthetic inhibition was mainly dominated by non-stomatal limiting factors.The dynamic changes of quantum yield of regulated energy dissipation［Y（NPQ）］，non-regulated energy dissipation［Y（NO）］and non-photochemical quenching（NPQ）were the most significant，indicating that the fluorescence index was more sensitive to PA-2 treatment.The content of O₂·⁻ and H₂O₂ in the leaves of treatment group was significantly higher than that of control，and it showed obvious enrichment in the leaves on the 7th day. <bold>Conclusion</bold> Strain PA-2 fermentation broth could inhibit the activity of photosynthetic electron transport chain and destroy the homeostasis of antioxidant system，resulting in excessive accumulation of ROS and failure of photosynthetic assimilation ability，and ultimately causing physiological damage to the leaves of <italic>C</italic>. <italic>album</italic>.