Pyrethroids are plant protecting substances whose effects on treated plants are widely monitored with often conflicting results. Field experiments showed no alteration in photosynthetic rates by a synthetic pyrethroid permethrin (Haile et al. 1999), while other studies showed an inhibition in PSII reactions by the halogen side of the molecules, and suggested QA as a target site of interaction, like in the case of urea-type herbicides (Bader and Schuler 1996). In order to clarify these opposing observations, photosynthetic effects of pyrethroids were re-tested
