Dcmu
Encyclopedia
DCMU is an herbicide
that inhibits photosynthesis
. It was introduced by Bayer
in 1954 under the trade name of Diuron.
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 blocks the ability of the plant to turn light energy into chemical energy (ATP
and reductant potential).
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
.
However, because it absorbs electrons oxidized from water in PS II, the electron "hole" of PS I cannot be satisfied, effectively shutting down photosynthesis by blocking the reduction of NADP+ to NADPH, and the cyclic photosynthetic pathway since electron shuttling is associated with proton pumping across the membrane into the lumen
.
Because of these effects, DCMU is often used to study energy flow in photosynthesis
.
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
that inhibits photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. It was introduced by Bayer
Bayer
Bayer AG is a chemical and pharmaceutical company founded in Barmen , Germany in 1863. It is headquartered in Leverkusen, North Rhine-Westphalia, Germany and well known for its original brand of aspirin.-History:...
in 1954 under the trade name of Diuron.
Mechanism of action
DCMU is a very specific and sensitive inhibitor of photosynthesis. It blocks the plastoquinonePlastoquinone
Plastoquinone is a quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. Plastoquinone is reduced , forming plastoquinol...
binding site of photosystem
Photosystem
Photosystems are functional and structural units of protein complexes involved in photosynthesis that together carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons...
II, disallowing the electron flow from where it is generated, in photosystem II, to plastoquinone. This interrupts the photosynthetic electron transport chain
Electron transport chain
An electron transport chain couples electron transfer between an electron donor and an electron acceptor with the transfer of H+ ions across a membrane. The resulting electrochemical proton gradient is used to generate chemical energy in the form of adenosine triphosphate...
in photosynthesis and thus blocks the ability of the plant to turn light energy into chemical energy (ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
and reductant potential).
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
Calvin cycle
The Calvin cycle or Calvin–Benson-Bassham cycle or reductive pentose phosphate cycle or C3 cycle or CBB cycle is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms...
.
However, because it absorbs electrons oxidized from water in PS II, the electron "hole" of PS I cannot be satisfied, effectively shutting down photosynthesis by blocking the reduction of NADP+ to NADPH, and the cyclic photosynthetic pathway since electron shuttling is associated with proton pumping across the membrane into the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
.
Because of these effects, DCMU is often used to study energy flow in photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
.