Is There a Place for New Herbicides Targeting Photosynthetic Electron Transport?

Abstract

Due to increased food demand, the need for use of herbicides is both necessary and on the rise. Several herbicide classes target photosynthetic electron transport: HRAC Groups 5, 6 and 22. These herbicides are used in large amounts in many different cropping systems to control several species of broadleaf and grass weeds. This article provides a comprehensive review of what these photosynthesis inhibitors are, how they are used and their mode of action. Presently, commercial herbicides only inhibit electron flow at two different sites photosystem II (PSII) and photosystem I (PSI). Those which inhibit electron flow at PSII block the movement of electrons down the electron transport chain, while those which inhibit at PSI accept electrons. Necrosis developing on the leaves of plants treated with PSII and PSI inhibitors is due to the accumulation of reactive oxygen species. Evolution of resistance, toxicity concerns, and other limitations of these herbicides call for the exploration of new chemistries which can be used to target this pathway.