sorgoleone

Sorgoleone is a potent, lipophilic allelopathic compound produced by the roots of Sorghum bicolor (L.) Moench. It is one of the major constituents of sorghum root exudates and is considered a key factor in the plant’s natural weed-suppressive properties. The molecule is a long-chain benzoquinone with a hydrophobic aliphatic side chain, making it highly insoluble in water and prone to sorption to soil organic matter.

Biological activity and mechanism: Sorgoleone acts as a photosynthesis inhibitor in susceptible plant species. It targets the photosystem II reaction center by interfering with the plastoquinone binding site (the QB site), thereby disrupting electron transport and reducing photosynthetic efficiency. The result is inhibited growth, chlorosis, and necrosis in exposed tissues, particularly in young seedlings and rapidly growing shoots.

Ecology and agronomic relevance: Sorghum bicolor releases sorgoleone into the rhizosphere through root exudation, contributing to its weed-suppressive effect in agricultural and natural ecosystems. The extent of activity in the field depends on factors such as soil moisture, temperature, organic matter content, and microbial degradation. Because of its hydrophobic nature, sorgoleone tends to be less mobile in soil, but it can accumulate near the root zone and in the upper soil layers where exudation is greatest.

Research and potential use: Sorgoleone has attracted interest as a natural herbicide lead due to its high potency at low concentrations. Challenges for practical use include variability in exudation among sorghum varieties, environmental fate and persistence, potential crop phytotoxicity, and formulation for field application. Ongoing work investigates its biosynthesis, regulation, and strategies to exploit sorgoleone-rich residues for weed management.