Physiological mechanism by which H₂O₂ soaking treatments promote the germination of Cyperus esculentus

Tiger nuts (Cyperus esculentus) are a new oil crop with drought tolerance, low water consumption, and high yield characteristics. They can be used as grains, oil, and feed. The sudden low temperatures during summer in North China and late spring in South China are unsuitable for the germination and growth of tiger nuts. In this study, round-grained tiger nuts were used as materials to study the effects of temperature (15, 20, 25, 30, 35, and 40 ℃) and H₂O₂ soaking treatments (0.01%, 0.1%, 1%, 3%, and 5%) on the germination ratio of tiger nuts and ascertain the mechanism by which H₂O₂ promotes tiger nut germination. The results showed that temperature played a major role in the germination of tiger nuts. The optimum temperature for germination of tiger nuts was 35 ℃. Tiger nut germination was significantly inhibited at 20 ℃, and could not germinate at temperatures lower than 15 ℃. H₂O₂ soaking treatment at 20 ℃ significantly promoted the germination ratio of tiger nuts (P < 0.05). Compared with those of the control, the germination ratio, germination potential, and germination index of tiger nuts treated with 1% H₂O₂ soaking increased from 51.67% to 98.33%, 18.33% to 95.00%, and 2.89 to 36.83, respectively, and the average germination days reduced from 7.86 days to 5.54 days. The SOD, POD, CAT, and amylase activities in tiger nuts tubers soaked in 1% H₂O₂ first increased and then decreased; the treatment resulted in lower malondialdehyde content and higher soluble sugar and soluble protein contents. There was a significant increase in IAA and GA₃ contents (P < 0.05) in seeds soaked in 1% H₂O₂, but ABA content first increased and then decreased. In conclusion, soaking tiger nuts in 1% H₂O₂ can enhance their germination capacity under temperature stress. H₂O₂ promotes the germination of tiger nuts under temperature stress mainly through the regulation of endogenous hormone levels, antioxidant enzyme activity, and soluble sugar and soluble protein contents.