Dynamics of release of allelochemical compounds from roots of wild oat (Avena fatua L.)

We explored the allelopathic potential of rhizospheric soil of wild oat (Avena fatua L.) during plant growth. Concentrations of phenolic compounds were determined in rhizosphere soil of plants grown under controlled conditions and harvested at four developmental stages (tillering, stem extension, heading, milky ripe). HPLC analysis showed production of seven phenolic compounds in rhizospheric soil of wild oat: 4-hydroxybenzoic acid, vanillic acid, syringic acid, vanillin, p-cumaric acid, syringaldehyde, ferulic acid. Higher total concentrations for these phenols in the rhizospheric soil were recorded at stem extension and heading (mean, 0.558 μg/kg soil dry matter). Syringic acid and vanillic acid showed the highest (0.138 μ/kg soil dry matter) and lowest (0.019 μ/kg soil dry matter) mean values, respectively, over all of the four developmental stages of plant growth. These data suggest that wild oat exudes allelopathic compounds and levels of phenolics into the rhizospheric soil vary according to plant maturity.