Abstract:

Objective: The aim of this study was to investigate the physiological characteristics of persimmon (Diospyros kaki) in the rooting process of softwood cutting, and to explore the dynamic changes and effects of endogenous hormones, oxidase activity and endogenous rooting inhibitor content, so as to provide technical and theoretical support for further study on the development mechanism of adventitious roots in persimmon softwood cutting and rapid propagation of excellent rootstock resources. Method: The semi-lignified twigs cut from 5-year-old grafted ‘Zhongshi 7’ persimmon seedling were used as experimental materials, and the cutting base was treated with special rooting agent for 30 s, and the rooting rate of cuttings was calculated in 35 days after cutting. The high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was used to determine the contents of auxin (IAA), abscisic acid (ABA), gibberellin (GA₃) and zeatin (ZR). The colorimetry was used to determine the activities of indoleacetic acid oxidase (IAAO), polyphenol oxidase (PPO), superoxide dismutase (SOD) and oxidoreductase (POD) and the contents of total phenols (TP), total flavonoids (TF) and total tannins (TT). Result: 1) The rooting process of persimmon softwood cutting was able to be divided into root primordium induction period (0–15 days), adventitious root expression period (15–25 days) and adventitious root elongation period (25–35 days). At the adventitious root expression stage, young white adventitious roots were able to be observed breaking through the cortex at the base of the cuttings. The rooting type of persimmon shoot cuttings was dominated by bark-derived rooting and mixed rooting, and the rooting rate of persimmon shoot cuttings was able to reach up to 82.33%, with an average root length of 6.54 cm, and an average number of roots per cutting up to 6.80 roots. 2) The endogenous hormone contents of persimmon shoot cuttings changed with the rooting process, in which the contents of IAA and ZR increased gradually, and the content of ABA increased first and then decreased, and reached the maximum at 20 days, while the content of GA₃ decreased gradually. IAA, GA₃, ABA and ZR played different roles in root primordium induction and adventitious root formation. 3) The rooting of persimmon cuttings was closely related to the activity of oxidase. Among them, the activities of SOD and PPO were stable at first and then decreased, and the activities of SOD and PPO maintained high for 15 days until the root primordium induction period when they significantly decreased. The POD activity increased at first and then decreased, and reached the maximum in 20 days of cutting. The IAAO activity decreased gradually, and at the same time the IAA content increased. 4) The rooting of persimmon softwood cuttings was closely related to endogenous rooting inhibitors, and the contents of total phenols, total flavonoids and total tannins decreased first and then increased slightly, reaching the lowest value in 25 days of cutting, but slightly increasing in 35 days of cutting. Conclusion: During the rooting process of persimmon softwood cuttings, the increase of IAA content and the decrease of endogenous rooting inhibitors such as total phenols, total flavonoids and total tannins are the key factors for inducing adventitious root formation. At the same time, the increase of ZR content, the decrease of GA₃ and ABA content, and the decrease of IAAO activity are closely related to the rooting.

Key words: Diospyros kaki, softwood cutting, endogenous hormones, oxidases, phenolic substance.