<P> DCMU is a very specific and sensitive inhibitor of photosynthesis . It blocks the plastoquinone binding site of photosystem II, disallowing the electron flow from where it is generated, in photosystem II, to plastoquinone . This interrupts the photosynthetic electron transport chain in photosynthesis and thus reduces the ability of the plant to turn light energy into chemical energy (ATP and reductant potential). </P> <P> DCMU only blocks electron flow from photosystem II, it has no effect on photosystem I or other reactions in photosynthesis, such as light absorption or carbon fixation in the Calvin cycle . </P> <P> However, because it absorbs electrons oxidized from water in PS II, the electron "hole" of PS I cannot be satisfied, effectively shutting down "linear" photosynthesis by blocking the reduction of NADP to NADPH . At the same time, it was found that DCMU not only does not inhibit the cyclic photosynthetic pathway, but, under certain circumstances, actually stimulates it . </P> <P> Because of these effects, DCMU is often used to study energy flow in photosynthesis . </P>

Dcmu inhibits electron transport in chloroplast by preventing the reduction of