Topramezone belongs to the pyrazolone class of herbicides, which act by inhibiting the enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD). Other herbicides that inhibit HPPD in plants, depleting plastoquinone and carotenoids and causing characteristic plant bleaching, include mesotrione, tembotrione, and isoxaflutole (National Center for Biotechnology Information 2019; EPA, 2005).
In Chlorella vulgaris, Topramezone altered pigment content, disrupted photosynthesis-related gene expression, increased ROS production, increased MDA concentrations, damaged membranes, and impaired cell integrity. The authors proposed that oxidative stress was a central event in algal toxicity. In algae, ROS appears to arise from damage to the photosynthetic apparatus, where electron . . .
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