Which herbicide interferes with photosynthetic electron transport and is associated with the phrase 'don't be a buzz kill'?

• A. Paraquat
• B. Glyphosate
• C. Atrazine
• D. 2,4-D

Answer: (A)

Paraquat works by disrupting photosynthetic electron transport through redox cycling at photosystem I. It acts as an electron acceptor, pulling electrons away from the chain and transferring them to molecular oxygen to form reactive oxygen species. This rapid oxidative stress damages chloroplast membranes and halts photosynthesis, leading to quick tissue death. That direct interference with the electrons moving through the photosynthetic machinery is what makes this herbicide distinctive for this mechanism.

Glyphosate acts on the shikimate pathway (EPSP synthase), not the electron transport chain. Atrazine blocks electron transport too, but at a different site (the plastoquinone/Photosystem II region), whereas 2,4-D disrupts growth regulation as an auxin mimic. The phrase serves as a mnemonic cue to remember paraquat’s oxidative, electron-transport–disrupting action.