Photosynthetic and Physiological Responses of Different Maize Varieties to Mesotrione.

Mesotrione (MET) belongs to the p-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting class of maize post-emergence herbicides, and it is safe for maize at the recommended doses, but the safety of MET differs among maize varieties in actual field production. In this study, four different maize varieties, ZD958, SN3, ST6 and POP16, were used as experimental materials to analyze their physiological responses to MET by comparing the activities of photosynthesis and antioxidant enzymes as well as the HPPD activity. The results showed that ZD958 was the most resistant to MET, followed by SN3 and ST6, and POP16 was the most sensitive to MET. The primary photosynthetic and antioxidant enzyme indices of all four maize varieties indicated that the resistant variety ZD958 was significantly higher than the sensitive variety POP16. HPPD activity was highest in ZD958 followed by SN3 and ST6 in both treated and control groups. POP16 exhibited the lowest HPPD activity. The results showed that the differences in resistance to MET in different types of maize varieties were closely related to the photosynthetic efficiency of plants and the HPPD activity. MET had minimal impact on common maize but showed a significant effect on popcorn. [ABSTRACT FROM AUTHOR]