Effect of auxin treatments, cuttings' collection date and initial characteristics on Paeonia 'Yang Fei Chu Yu' cutting propagation.

Abstract Paeonia ‘Yang Fei Chu Yu’ is one of the most popular and commercially valuable cultivars of herbaceous peony. The study was performed to explore propagation techniques by cuttings for the nursery industry. Results showed that the stem cuttings pretreated with 2000 mg L −1 indole-3-butyric acid (IBA) in quick-dip method got the best rooting traits (rooting percentage is 86.7%, root number is 23.1 and root length per rooted cutting is 6.4 cm). Therefore pre-treatment with 2000 mg L −1 IBA is recommended. To establish the optimum cuttings’ collection date and interpret better the relation between the rooting ability and the cutting material's initial physiological characteristics, three collection periods were designed after florescence and the stem cuttings’ endogenous factors (nutrient reserves and hormones) were examined. The results showed stem cuttings collected at the 70th day after florescence rooted best, and then cuttings collected at the 40th day, while those taken at the 10th day worst. Among the three collection dates, the soluble carbohydrate level had no statistically significant difference, but its increasing concentration was positively related to the cuttings’ rooting potential. The nitrogen level decreased with the delaying of cuttings’ collection and the difference was significant. This tendency implicated the negative relation between the nitrogen level and the cuttings’ rooting potential. Among the four determined endogenous plant hormones, both gibberellic acid (GA 3 ) and abscisic acid (ABA) content had no significant seasonal difference, while indole-3-acetic acid (IAA) and zeatin riboside (ZR) content significantly varied with collection date. IAA content was the highest at the 10th day after florescence and subsequently significantly decreased with the delaying of cuttings’ collection date, whereas ZR content exhibited the contrary tendency.