Paraquat

Paraquat is a fast-acting, nonselective herbicide that damages green plant tissue on contact. It is highly toxic to humans and other animals.

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Redox cycling: A process in which a compound repeatedly gains and loses electrons, transferring them to other molecules. Paraquat repeatedly accepts electrons from photosynthetic systems and transfers them to oxygen.
Desiccation: The removal or loss of moisture from a material or organism. Paraquat has been used to dry crop foliage before harvest.
Glyphosate: A systemic, broad-spectrum herbicide that inhibits the plant enzyme EPSP synthase. Unlike paraquat, glyphosate moves through plants and acts through a different biochemical target.
Pulmonary fibrosis: Scarring and thickening of lung tissue that can impair oxygen exchange. Survivors of severe paraquat poisoning may develop progressive lung damage and fibrosis.
Photosystem I: A protein complex in chloroplast thylakoid membranes that uses light energy to transfer electrons. It supplies electrons that paraquat diverts from normal photosynthetic pathways.
No-till farming: Crop production that minimizes or avoids soil tillage between plantings. Paraquat can control weeds without mechanically disturbing the soil.
Diquat: A bipyridyl herbicide that causes rapid tissue injury through redox cycling. Diquat resembles paraquat in action but differs in toxicological profile and uses.
Toxicology: The study of harmful effects of chemicals on living organisms. Paraquat’s poisoning risks are central to decisions about handling and use.
Reactive oxygen species: Reactive oxygen-containing molecules that can oxidize and damage cellular components. Paraquat-driven oxygen reduction produces these agents, which injure membranes and other cell structures.
Weed control: The prevention or reduction of unwanted plants in agricultural or managed settings. Paraquat is used to suppress weeds in settings where its use is legally permitted.