Objective This paper explores the effects of endogenous inhibitors (such as phenolic acids and flavonoids) produced by ancient Platycladus orientalis trees of different ages on rooting during the cutting process, so as to provide a theoretical basis for improving the rooting rate of ancient P. orientalis cuttings.

Method The cuttings from 5-, 100-, 300-, and 700-year-old P. orientalis were used as experimental materials for cutting propagation. The effects of extracts from the cuttings of P. orientalis of different ages (5-, 100-, 300-, and 700-year-old) in March and June on the germination of cabbage seeds were studied, and the contents of phenolic acids and flavonoids in the cuttings were measured to compare the effects of phenolic acids and flavonoids produced during the rooting process of cuttings of P. orientalis trees of different ages from June on the rooting process. Screening different removal methods was to identify the optimal approach for eliminating inhibitors from 100-year-old P. orientalis cuttings.

Result (1) The rooting rates and root numbers of ancient P. orientalis trees (100-, 300-, and 700-year-old) were significantly lower than those of young P. orientalis trees (5-year-old ) (P < 0.05). (2) The inhibitory effects of extracts from 100-, 300-, and 700-year-old P. orientalis cuttings on cabbage seed germination in March were significantly higher than that in June (P < 0.05). As the ages of trees increased, the inhibitory effects of extracts of cuttings on inhibiting the germination of cabbage seeds increased. (3) The contents of phenolic acids and flavonoids in P. orientalis cuttings from June were generally low. In the experimental materials from March and June, the contents of rutin, salicylic acid, gallic acid, coumaric acid, and ferulic acid generally showed an increasing trend with the increase of age of P. orientalis. In the experimental materials from June, the phenolic acid and flavonoid contents of 5-, 100-, 300-, and 700-year-old P. orientalis cuttings showed an increasing trend with the development of rooting process. (4) Treating cuttings of ancient P. orientalis with 0.1% silver nitrate solution can promote the formation of adventitious roots, and treating them with 0.05% potassium permanganate solution can promote root development.

Conclusion As the age of P. orientalis grows, the phenolic acid and flavonoid contents of cuttings increase, which have inhibitory effects on the formation of adventitious roots. However, treatment of P. orientalis cuttings with 0.1% silver nitrate or 0.05% potassium permanganate can effectively alleviate this inhibitory effect and improve the rooting rates of P. orientalis cuttings. The study provides theoretical basis and technical support for improving rooting rates.