Chemical refinement of smoke water and wood vinegar and identification of catechol as a phenolic compound inhibiting rice root growth under low-phosphorus conditions

บทคัดย่อ

Smoke-derived liquids such as smoke water (SW) and wood vinegar (WV) contain diverse pyrolysis products with potential bioactivity in plants, yet their chemical determinants of growth promotion and inhibition remain unclear. Our previous work showed that SW promotes rice root elongation under phosphorus deficiency, but whether WV exerts similar effects has not been examined. Here, we compared the physicochemical properties, chemical composition, and biological activity of SW, WV, and their activated-carbon-treated forms (AC-SW and AC-WV) under low-phosphorus (LP) conditions. Both SW and WV stimulated root growth at low concentrations but inhibited it at higher doses, with WV showing stronger phytotoxicity. Activated-carbon (AC) refinement mitigated this inhibition, restoring root elongation and reducing root darkening. GC-MS analysis revealed that acetic acid was the dominant compound across all samples, while WV exhibited higher proportions of phenolic compounds, particularly catechol, syringol, and related dimethoxyphenols, which were largely removed following AC treatment. Bioassays confirmed that catechol alone inhibited rice root growth and induced darkening under LP conditions, identifying it as a key inhibitory constituent of WV. These results demonstrate that phenolic enrichment underlies the phytotoxicity of concentrated WV and that simple AC treatment can effectively reduce these compounds, improving the plant compatibility of smoke-derived biostimulants.