Wood Vinegar Enhances Seedling Rate of Rice Seeds under Flooding Stress by Mitigating Oxidative Damage and Maintaining Energy Homeostasis

Abstract

Flooding stress is a major adverse condition during the emergence period of direct-seeded rice. This study investigated the use of wood vinegar as a seed soaking treatment to enhance rice seedling rates under flooding stress, exploring both the methodology and physiological mechanisms involved. The optimal seed soaking concentration was determined through a gradient experiment, followed by a multi-cultivar validation test. The physiological mechanism of wood vinegar soaking on seedling emergence was analyzed by measuring the electrical conductivity of the flooding water, the changes in starch and soluble sugar contents in the grains and sprouts, and the dynamics of α-amylase activity and antioxidant-related enzyme activities in the sprouts. The results showed that soaking rice seeds in a wood vinegar solution at a low concentration significantly enhanced the emergence of rice seedlings under flooding conditions, with a 100-fold dilution having the most pronounced effect, increasing seedling rates by 50.6%–60.0%. Further analysis indicated that wood vinegar treatment enhanced seedling establishment by inducing a significant increase in α-amylase activity, leading to a 74.9%–213.6% increase in soluble sugar content in the sprouts during 2–8 d after flooding stress compared with the control. Additionally, the treatment increased superoxide dismutase and peroxidase activities in the sprouts, mitigating lipid peroxidation of the cell membranes, and notably lower water electrical conductivity was observed in wood vinegar-treated seeds compared with the control. In conclusion, soaking rice seeds in a 100-fold diluted wood vinegar solution improves rice seedling rates under flooding stress by mitigating oxidative damage and maintaining energy supply. This approach is valuable for developing cost-effective seed treatment technologies and offering novel strategies to improve seedling rates and uniformity of direct-seeded rice under flooding conditions.