University of California
Herbicide Symptoms

Glutamine Synthesis Inhibitors

HRAC Group: H

WSSA Group: 10

Glufosinate is the only commercialized glutamine synthetase herbicide in the United States. Glufosinate belongs to phosphinic acid chemistry. It is a broad-spectrum postemergent herbicide that controls most annual grasses and broadleaves. It is a contact herbicide with limited translocation throughout the plant. The glutamine synthetase herbicides inhibit activity of glutamine synthetas, the enzyme that converts glutamate and ammonia to glutamine. This inhibition results in massive accumulation of ammonia in a plant which destroys cells and directly inhibits photosystem I and photosystem II reactions. High ammonia in plants reduces the pH gradient across the membranes which inhibits energy production needed to support plant growth and development.

Injury symptoms: Injury symptoms appear as foliar burning within several hours following exposure. Perennial and large annual plants will often recover from injury and sometimes initiate regrowth from auxiliary buds. Injury symptoms are leaf burning, yellowing, browning, leaf distortion, leaf crinkling, and necrosis.

Chemistry Group and Common Names of GS Inhibitors
Used in the United States

Chemistry Common Name
Phosphinic acids Glufosinate-ammonium


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