Eight p-benzoquinone derivatives (S1-S8) were evaluated as photosynthesis inhibitor through chlorophyll a (Chl a) fluorescence assays. The photosynthetic parameters analysed at in vitro and in vivo experiments based on the principal phases of the photosynthetic process: the absorption of photons (ABS), trapping energy (TR), electron transport (ET) and reduction of final acceptors of photosystem II (RE). The photosynthetic apparatus damage was measured by the biophysical parameters derived from the OJIP transients: performance index (PIABS), specific energy fluxes per reaction centre (ABS/RC; TRo/RC and ETo/RC), phenomenological energy fluxes per cross section (ABS/CSo; TRo/CS and ETo/CS) and quantic yield (PHI(Po); PHI(Eo); PSIo and PHI(DO)). The compounds S3 at 150 µM and S8 at 300 µM showed a significant activity on electron transport inhibition on photosystem II (PSII), decreasing by 40 and 75% the parameter PI(abs), respectively, that indicates a stress on photosynthetic apparatus. Compound S3 (150 µM) decreased by 23% the parameters quantic yield and Eto/RC, demonstrating the stress on PSII is on electron transport. Compound S8 (300 µM) decreased by approximately 20% the parameters ETo/RC, RC/CSo, TRo/CSo and ETo/CSo, indicating that there is partial blockage in the electron flow in the reaction centre. Furthermore compound S8 (300 µM) reduced by 50% plant growth at dry biomass experiment and inhibited germination seeds by 90% at 200 mM concentration. The results showed that compound S8 has photosynthetic and plant growth inhibitory activity, indicating that p-benzoquinone derivatives have promising potential to be explored as a tool in further development of herbicide.