Effect of Pyrolysis Temperature on the Characteristics of Wood Vinegar Derived from Chinese Fir Waste: A Comprehensive Study on Its Growth Regulation Performance and Mechanism

[Image: see text] As a high value-added product from biomass pyrolysis, wood vinegar (WV) has been used as a growth regulator for many plant species in agriculture based on the diverse active chemical compounds present. To reveal the relationship between chemical constituents and regulation performance, four kinds of WVs were prepared by slow pyrolysis from Chinese fir waste at different temperature ranges. The chemical constituents of WVs were analyzed by gas chromatography–mass spectrometry, and the regulation performance of WVs was investigated from the aspects of seed germination and root growth of wheat. The results indicated that the chemical constituents of WVs were affected obviously by pyrolysis temperature and the major components were acids and phenols. All types of WVs showed regulation performance but with different effects and levels. The WV collected from 20 to 150 °C exhibited a promoting effect and other three WVs exhibited inhibiting effects. It was considered that the regulation performance of WV was relevant to acids and phenols through a synergy mechanism. Acids caused intercellular acidification and increased root activity, which promoted the seed germination and root growth, while phenols increased the content of malonaldehyde, indicating that phenols caused the oxidative stress to damage cell structure and inhibit growth. All these results could be a reference for further utilization of WVs as a sustainable alternative to chemicals for plant growth regulation in agriculture.