ClO2 treatment delays petal senescence and extends the vase life of Paeonia suffruticosa ‘Luoyang Hong’ cut flowers

Chlorine dioxide (ClO2) is an effective fungicide that can be used to mitigate post-harvest mechanical damage and bacterial contamination that can negatively affect the quality and longevity of fresh-cut flowers. To further explore the role of ClO2 in the preservation of peony cut flowers, we set different concentrations of ClO2 (0, 0.025, 0.050, 0.075, and 0.100 g·L−1), and we found that the 0.100 g·L−1 ClO2 treatment extended the vase for 3.2 days longer than CK. The ClO2 treatment increased water uptake of cut flowers by 37.5 % compared to CK, thus maintaining a higher fresh weight. It also retarded the reduction of soluble sugars and proteins. In addition, ClO2 treatment increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) by 30.9 %, 31.5 %, and 10.0 % each, respectively, and decreased the levels of malondialdehyde and hydrogen peroxide, respectively, when compared with CK. To further investigate its mechanism of action, the morphological characteristics of the stem bases of treated and untreated peony cut flowers were analyzed by using a bacterial inhibition assay and scanning electron microscopy (SEM), and ClO2 not only inhibited the growth of stem-end bacteria but also reduced the lignin content and the activities of related enzymes. In addition, ethylene production decreased after 0.100 g·L−1 ClO2 treatment, which might be related to the down-regulation of the ethylene synthase gene PsACO1. The expression of ethylene signaling genes PsETR1, PsEIL3, and PsERF1 was also affected. Therefore, the ClO2 treatment might be used as a bactericide to enhance the vase life of P. suffruticosa 'Luoyang Hong' cut flowers.