Effect of Paclobutrazol Application on Plant Growth and Flower Quality inHerbaceous Peony

Herbaceous peony (Paeonia lactifloraPall.) is an important ornamental plant worldwide. In its natural state,P.lactifloraoften manifests traits like rapidly elongating internodal growth, loose plant types, and soft inflorescencestems. However, very little has been known about the measures for controlling these traits. This study investigatedthe effect of applying paclobutrazol (PBZ) on the plant growth andflower quality inP. lactiflora. The results indi-cated that PBZ application reduced the plant height (8.05%), plant crown width (14.72%), and leaf area (10.90%),but increased the leaf thickness (18.18%) and stem diameter (over 11%) inP. lactiflora. Meanwhile, PBZ applica-tion was also found to increase the chlorophyll (Chl) a (29.63%), Chl b (33.33%), Chl a+b (30.56%), SPAD(27.32%), relative water content (0.47%), soluble sugar (5.09%) and activities of three antioxidant enzymes (super-oxide dismutase 169.66%, peroxidase 3.59%, catalase 319.30%), but decreased the relative electrical conductivity(18.52%). Additionally, the application of PBZ was found to affect theflowering quality ofP. lactiflora, increasingtheflower diameter and fresh weight only in theflower-bud stage. This initiates the bloom stage, where there wasa decrease in the total content of the aromatic compounds except for theflower-bud stage, and faded theflowercolor by reducing the content of anthocyanin. These results demonstrated that the application of PBZ can regulatetheP. lactifloraplant types with no significant decrease in its ornamental values. This might provide a theoreticalbasis for further applying PBZ inP. lactiflorafor use in urban landscape spaces