Effects of imazethapyr spraying on plant growth and leaf surface microbial communities in Arabidopsis thaliana

Imazethapyr (IM) is an acetolactate synthase (ALS)-inhibiting herbicide that has been widely used in recent years. However, IM spraying can lead to the accumulation of herbicide residues in leaves. Here, we determined the effects of IM spraying on the plant growth and leaf surface microbial communities of Arabidopsis thaliana after 7 and 14 days of exposure. The results suggested that IM spraying inhibited plant growth. Fresh weight decreased to 48% and 26% of the control value after 7 and 14 days, respectively, of 0.035 kg/ha IM exposure. In addition, anthocyanin content increased 9.2-fold and 37.2-fold relative to the control content after 7 and 14 days of treatment, respectively. Furthermore, IM spraying destroyed the cell structures of the leaves, as evidenced by increases in the number of starch granules and the stomatal closure rate. Reductions in photosynthetic efficiency and antioxidant enzyme activity were observed after IM spraying, especially after 14 days of exposure. The diversity and evenness of the leaf microbiota were not affected by IM treatment, but the composition of community structure at the genus level was altered by IM spraying. Imazethapyr application increased the abundance of Pseudomonas, a genus that includes species pathogenic to plants and humans, indicating that IM potentially increased the abundance of pathogenic bacteria on leaves. Our findings increase our understanding of the relationships between herbicide application and the microbial community structures on plant leaves, and they provide a new perspective for studying the ecological safety of herbicide usage.