To clarify the photoacclimation and stress-resistance coupling strategies of maize (Zea mays L.) variety B73 under Ostrinia furnacalis (Guenée) herbivory, we compared herbivory with mechanical damage and exogenous salicylic acid (SA)/methyl jasmonate (MeJA) treatments, focusing on the relationship between photosynthesis and defense. Results showed that O. furnacalis herbivory significantly reduced chlorophyll fluorescence and gas-exchange parameters, impairing light energy capture and conversion, and induced a progressive shift in photosynthetic performance associated with dynamic changes in carbon acquisition and utilization. Although herbivory and MeJA elicitation induced similar phenotypic changes after 12 h, herbivory caused much stronger global downregulation of photosynthesis-related genes than mechanical damage and hormone treatments. All stress treatments increased total antioxidant capacity (T-AOC) and reactive oxygen species (ROS, H₂O₂ and O₂·⁻) levels; notably, soluble protein (SP) explained 30.09% of the variance in the trade-off between photosynthetic pigment degradation and stress tolerance. Network modeling of photosynthetic genes, chlorophyll fluorescence parameters, gas-exchange parameters, and resistance-defense traits demonstrated robust modular connectivity, identifying chlorophyll fluorescence and gas-exchange parameters as core modulators of the resistance-defense trade-off. Collectively, maize adapts to external stress by balancing photosynthetic downregulation and defense enhancement through coordinated regulation of photosynthetic performance, antioxidant capacity, and core photosynthetic gene expression. These findings provide new insights into the mechanisms underlying plant stress tolerance.

Diflufenican is a herbicide widely used in agricultural systems, but its effects on soil bacterial communities across different soil depths remain insufficiently understood. In this study, we investigated depth-resolved bacterial community responses and functional potential following diflufenican perturbation in agricultural soils. Soil samples collected from different depths were incubated with or without diflufenican, and bacterial communities were analyzed using 16S rRNA gene amplicon sequencing. Co-occurrence network analysis was conducted to explore potential bacterial association patterns, and PICRUSt2 and FAPROTAX were used to infer bacterial functional potential. Diflufenican perturbation altered bacterial alpha diversity and reshaped community composition, with response patterns varying among soil depths. Principal coordinate analysis based on Bray–Curtis dissimilarity showed separation between control and diflufenican-treated soils, indicating treatment-associated shifts in bacterial community structure. Several genera, including Sphingomonas, Pseudarthrobacter, Bacillus, Microvirga, and Phenylobacterium, were enriched in diflufenican-treated soils, suggesting that they may represent candidate diflufenican-associated taxa. Co-occurrence network analysis further indicated changes in potential bacterial association patterns after diflufenican perturbation. Functional inference suggested shifts in bacterial functional potential, particularly in nutrient cycling-related functions, and these shifts differed among soil depths. Overall, these findings indicate that diflufenican perturbation reshapes soil bacterial community structure and alters inferred functional potential in a depth-dependent manner, highlighting the importance of soil vertical depth in assessing herbicide impacts on agricultural soil microbiomes.