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

doi:10.1016/j.rsci.2025.08.006

Abstract

Abstract:

Flooding stress is a majo 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.

Key words: rice, flooding stress, wood vinegar, α-amylase, antioxidant enzyme

Zhu Junlin, Zheng Guangjie, Tao Yi, Liao Wenli, Ye Chang, Xu Ya’nan, Xiao Deshun, Chu Guang, Xu Chunmei, Wang Danying. Wood Vinegar Enhances Seedling Rate of Rice Seeds under Flooding Stress by Mitigating Oxidative Damage and Maintaining Energy Homeostasis[J]. Rice Science, 2026, 33(1): 129-140.

Figures/Tables 9

Fig. 1. Changes of water electrical conductivity (A), agronomic traits (B), and plant phenotype (C) under different wood vinegar soaking treatments. ZJ8, Zhongjia 8; ZJZ17, Zhongjiazao 17; CK, Control group (pure water); C1, C2, C3, C4, C5, and C6 were seeds soaked with wood vinegar dilutions of 25-, 50-, 75-, 100-, 125-, and 150-fold, respectively. In B, data are mean ± SD (n = 3). Different lowercase letters above bars indicate significant differences at P < 0.05 by the Duncan’s test.

Table 1. Effect of 100-fold diluted wood vinegar on agronomic characters of rice.

Cultivar type	Cultivar	Seedling rate (%)		Sprout growth (cm)			Dry matter accumulation (mg)
Cultivar type	Cultivar	Control	C4 treatment	Control	C4 treatment		Control	C4 treatment
Inbred indica rice	Zhongzao 48	0.00 ± 0.00	75.67 ± 4.16**	-	3.04 ± 0.07	-		5.38 ± 0.41
	Zhongzao 39	1.33 ± 1.54	81.67 ± 9.50**	1.23 ± 0.06	3.53 ± 0.07**	-		8.91 ± 0.34
	Yangdao 6	3.00 ± 2.65	88.67 ± 4.16**	2.62 ± 0.08	3.93 ± 0.02**	-		12.20 ± 0.53
	Zhe 1708	31.67 ± 7.09	95.66 ± 2.52**	2.41 ± 0.10	3.74 ± 0.21**	6.53 ± 0.57		10.76 ± 0.76**
Inbred japonica rice	Jia 58	98.67 ± 1.53	99.67 ± 0.58	4.73 ± 0.02	4.97 ± 0.06**	13.80 ± 0.20		15.67 ± 0.15**
	Zhejing 96	88.33 ± 2.31	92.00 ± 2.65	3.64 ± 0.15	4.64 ± 0.30**	10.41 ± 0.44		12.13 ± 0.84*
	Zhejing 99	35.67 ± 7.50	100.00 ± 0.00**	1.54 ± 0.03	4.27 ± 0.18**	5.60 ± 0.44		11.00 ± 0.79**
	Jia 67	95.33 ± 2.89	97.33 ± 1.53	3.94 ± 0.27	5.40 ± 0.44**	11.17 ± 0.47		12.30 ± 0.17*
Indica-japonica hybrid rice	Yongyou 1540	25.00 ± 16.46	99.67 ± 0.58**	2.68 ± 0.05	2.81 ± 0.07**	7.07 ± 0.15		7.67 ± 0.21*
	Yongyou 15	3.00 ± 1.73	90.67 ± 10.21**	1.78 ± 0.08	3.72 ± 0.48**	-		8.86 ± 0.57
	Zhehangyou 220	0.00 ± 0.00	70.67 ± 2.08**	-	3.54 ± 0.12	-		5.83 ± 0.32
	Chunyou 83	59.33 ± 8.08	90.67 ± 6.51**	3.01 ± 0.19	4.30 ± 0.13**	9.96 ± 0.60		12.03 ± 0.64*

Fig. 2. Effects of wood vinegar soaking on α-amylase activity, starch and soluble sugar contents in seeds (A) and seed starch degradation rate (B) under flooding stress. ZJ8, Zhongjia 8; ZJZ17, Zhongjiazao 17. CK, Control group (pure water); C4, 100-fold diluted wood vinegar solution. Data are mean ± SD (n = 3). * and ** represent significant differences at the 0.05 and 0.01 levels by the Duncan’s test. ns, No significance.

Fig. 3. Effects of wood vinegar soaking on soluble sugar content in sprouts under flooding stress. ZJ8, Zhongjia 8; ZJZ17, Zhongjiazao 17; CK, Control group (pure water); C4, 100-fold diluted wood vinegar solution. Data are mean ± SD (n = 3). * and ** represent significant differences at the 0.05 and 0.01 levels by the Duncan’s test.

Fig. 4. Effects of wood vinegar soaking on soluble protein content in sprouts under flooding stress. ZJ8, Zhongjia 8; ZJZ17, Zhongjiazao 17; CK, Control group (pure water); C4, 100-fold diluted wood vinegar solution. Data are mean ± SD (n = 3). * and ** represent significant differences at the 0.05 and 0.01 levels by the Duncan’s test. ns, No significance.

Fig. 5. Effects of seed soaking with wood vinegar on antioxidant enzyme activity (A) and isoenzyme of antioxidant enzyme (B) in sprouts under flooding stress. DAF, Days after flooding. ZJ8, Zhongjia 8; ZJZ17, Zhongjiazao 17; SOD, Superoxide dismutase; POD, Peroxidase; CAT, Catalase. Data are mean ± SD (n = 3). * and ** represent significant differences at the 0.05 and 0.01 levels by the Duncan’s test. ns, No significance.

Table 2. Correlation between seedling rate and physiological and biochemical indexes of seed soaked with wood vinegar under flooding stress.

Variety	Parameter	SR	EC	SG	SOD	POD	CAT	SP	α-Amy	Sta	SS
ZJ8	EC	-0.970**
	SG	0.969**	-0.968**
	SOD	0.962**	-0.996**	0.953**
	POD	0.929**	-0.927**	0.907*	0.893*
	CAT	-0.986**	0.983**	-0.972**	-0.968**	-0.958**
	SP	0.947**	-0.970**	0.903*	0.965**	0.938**	-0.949**
	α-Amy	0.953**	-0.993**	0.942**	0.995**	0.902*	-0.973**	0.958**
	Sta	-0.918**	0.982**	-0.940**	-0.987**	-0.851*	0.941**	-0.924**	-0.987**
	SS	0.991**	-0.980**	0.974**	0.968**	0.950**	-0.984**	0.968**	0.955**	-0.928**
	DS	0.985**	-0.995**	0.961**	0.991**	0.939**	-0.990**	0.978**	0.988**	-0.962**	0.988**
ZJZ17	EC	-0.964**
	SG	0.934**	-0.962**
	SOD	0.948**	-0.980**	0.983**
	POD	0.932**	-0.967**	0.954**	0.992**
	CAT	-0.943**	0.993**	-0.979**	-0.989**	-0.972**
	SP	0.833*	-0.910*	0.934**	0.945**	0.924**	-0.950**
	α-Amy	0.960**	-0.991**	0.987**	0.989**	0.971**	-0.992**	0.914*
	Sta	-0.939**	0.983**	-0.944**	-0.960**	-0.958**	0.968**	-0.850*	-0.982**
	SS	0.933**	-0.969**	0.993**	0.979**	0.958**	-0.977**	0.905*	0.993**	-0.970**
	DS	0.933**	-0.952**	0.995**	0.978**	0.954**	-0.964**	0.902*	0.984**	-0.949**	0.995**

Fig. 6. Changes of dissolved oxygen content (A) and morphological difference after 3 d of flooding (B) under flooding stress. ZJ8, Zhongjia 8; ZJZ17, Zhongjiazao 17; CK, Control group (pure water); C4, 100-fold diluted wood vinegar solution. Data are mean ± SD (n = 3).

Fig. 7. Schematic diagram of wood vinegar soaking rice seeds to alleviate flooding stress and promote seedling emergence. ATP, Adenosine triphosphate; O2·̄, Superoxide anion; SOD, Superoxide dismutase; POD, Peroxidase; CAT, Catalase; ROS, Reactive oxygen species; TCA, Trichloroacetic acid.

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