Responses of the antioxidant system to fluroxypyr in foxtail millet (Setaria italica L.) at the seedling stage

Foxtail millet (Setaria italica L.) is an important food and fodder crop in semi-arid areas. However, there are few herbicides suitable for use on weed control in field-grown foxtail millet during the post-emergence herbicides stage. The present study was conducted using four concentrations (0.5, 1, 2, and 4 L ai ha−1) of foliar-applied fluroxypyr, and the effect of fluroxypyr on selected metabolic and stress-related parameters in foxtail millet were assessed after 15 days. In this study, increasing concentrations decreased plant height and accumulation of chlorophylls. Our results also showed that malondialdehyde (MDA) accumulated in response to fluroxypyr application, demonstrating increased lipid peroxidation due to excessive reactive oxygen species production. In response to this oxidative stress, the activities of antioxidant enzymes were generally enhanced. Non-enzymatic antioxidant defense systems, which function in concert with antioxidant enzymes, can also protect plant cells from oxidative damage by scavenging reactive oxygen species (ROS). In conclusion, the hybrid variety (Zhangzagu) exhibited a greater tolerance to fluroxypyr than did the conventional variety Jingu 21, which might be associated with the antioxidant mechanisms of Zhangzagu hybrid millet.