INHIBITION OF ENERGY-TRANSFER FROM LIGHT HARVESTING CHLOROPHYLL-PROTEIN COMPLEX TO PHOTOSYSTEM-II BY OXYFLUORFEN

The effect of magnesium on the photochemical activity and fluorescence yield of chlorophyll a in vivo of oxyfluorfen-treated chloroplasts was studied. The magnesium-induced increase in Photosystem II activity at low light intensity was abolished by incubation of chloroplasts with oxyfluorfen. Photosystem I activity in the presence of Mg2+ was higher with than without oxyfluorfen. The magnesium-induced increase in fluorescence yield was progressively lowered with increasing concentration of oxyfluorfen. DCMU did not increase the fluorescence yield of high salt chloroplasts incubated with oxyfluorfen. These results suggest that oxyfluorfen inhibits energy transfer from LHC II to PS II and increases spill-over of energy from PS II to PS I. © 1990.