It is necessary to assess the direct effects of PSII herbicides on photosynthesis.
10">Phytotoxicity of bromacil is investigated in an enantiomeric level.
15">Bromacil disturbed enantioselectively the photosystem II of Arabidopsis thaliana.
S-bromacil caused severer damage to photosynthesis of Arabidopsis than R-bromacil.
Photosynthesis should be considered for phytotoxicity assessment of herbicides.