DQ (Diquat)
Definition and meaning of DQ (Diquat) in chemistry.
DQ, commonly known as diquat, is a fast-acting and nonselective agricultural contact herbicide. It functions primarily as a powerful crop desiccant to dry out plant tissues before harvesting. Diquat kills green plant tissue on contact by rapidly generating destructive reactive oxygen species. These extremely toxic oxygen molecules quickly destroy essential cell structures and cause the plant to wither.
In more detail
Diquat is a quaternary ammonium salt built from a complex fused bipyridyl ring system. It is most frequently sold and applied commercially as the highly soluble diquat dibromide salt. When exposed to natural sunlight, the diquat molecule easily enters the chloroplasts of the target plant.
It rapidly intercepts energized electrons directly from photosystem I during the natural photosynthesis process. This chemical interference creates a highly stable radical cation within the living plant cells. This radical cation immediately transfers its extra electron to surrounding atmospheric molecular oxygen.
This specific reaction produces superoxide and other incredibly damaging reactive oxygen chemical species. These strong chemical oxidants attack and completely rupture the plant cell membranes within a few hours. This massive cellular damage causes rapid wilting and severe browning of the green plant foliage.
Diquat only damages the specific green plant tissue that it directly contacts upon initial application. It does not move easily through the plant stems down into the underground root system. This limited physical movement makes it highly effective for controlling submerged and floating aquatic weeds.
Students often confuse contact herbicides like diquat with systemic agricultural herbicides like chemical glyphosate. Systemic herbicides travel throughout the entire plant, while diquat strictly kills the directly sprayed parts.
Key facts
| Field | Organic Chemistry |
|---|---|
| Chemical Formula | C12H12Br2N2 |
| Chemical Class | Bipyridylium quaternary ammonium |
| Target Site | Photosystem I in chloroplasts |
| Toxic Mechanism | Generates reactive oxygen species |
| Plant Mobility | Contact only (non-systemic) |
Diquat dibromide is frequently sprayed onto commercial potato fields just a few days before harvest. The chemical rapidly destroys the thick green leafy vines growing above the field soil. This deliberate destruction stops the underground potato tubers from growing any larger before collection. Removing the thick vines makes the heavy mechanical harvesting process much easier for local farmers.
Frequently asked questions
Is DQ or diquat the exact same chemical compound as the herbicide paraquat?
They are completely different chemicals with distinct molecular structures and separate government regulatory rules. Both are bipyridylium herbicides that rapidly kill plants using very destructive reactive oxygen species.
Why does the diquat chemical kill plants so much faster than systemic glyphosate?
Diquat directly short-circuits natural photosynthesis to produce membrane-destroying oxygen radicals within a few hours. Glyphosate must be slowly absorbed and moved to block plant amino acid synthesis over many days.
Does the applied diquat chemical permanently poison the agricultural soil after it is sprayed?
The diquat molecule has a strong positive charge that binds extremely tightly to soil clay particles. This immediate physical binding makes the chemical biologically inactive and completely prevents future root uptake.
Sources & references
See our sources and editorial standards.