Regulatory Effects of Different Doses of Penoxsulam on Endogenous Hormones and Antioxidant System in Foxtail Millet

The specific objectives include three points: (1) to clarify the dynamic change laws of the contents of three key endogenous hormones, namely, indole-3-acetic acid (IAA), gibberellin (GA), and abscisic acid (ABA), in foxtail millet leaves after penoxsulam treatment, and their correlations with drug dose and treatment time; (2) to analyze the effects of different doses of penoxsulam on the antioxidant system of foxtail millet, specifically including the change characteristics of hydrogen peroxide (H₂O₂), superoxide anion (O₂^-), reduced glutathione (GSH) content, and cell membrane permeability (MP); and (3) to reveal the correlation between endogenous hormone changes and antioxidant system indicators through correlation analysis so as to provide a direct experimental basis for the screening of safe doses of penoxsulam application in foxtail millet fields and the research on the herbicide stress resistance mechanism of foxtail millet. Using Jingu 21 as the test material, four penoxsulam dose levels were set through pot and field experiments. The changes in endogenous hormone content, antioxidant system indexes, and phenotypic indicators of foxtail millet were determined at different periods after treatment, and the correlation between endogenous hormones and antioxidant systems was analyzed. Compared with the control (P₀), the contents of IAA and GA in foxtail millet showed a "first increasing and then decreasing" trend, while the content of ABA showed a continuous increasing trend. With the increase in penoxsulam concentration, the contents of H₂O₂, O₂^-, GSH, and MP in foxtail millet gradually increased. A correlation analysis showed that there was a significant correlation between leaf endogenous hormones and the defense capacity of the antioxidant system. After penoxsulam treatment, foxtail millet leaves showed dynamic changes of "first increasing and then decreasing" in IAA and GA contents, and a continuous increase in ABA contents. At the same time, H₂O₂, O₂^-, GSH content, and MP increased significantly with the increase in the drug dose. It is speculated that foxtail millet may indirectly regulate the defense ability of the antioxidant system by regulating the content of endogenous hormones to alleviate the damage of herbicide stress.