A composite vase solution improved vase quality of cut peony after long-term cold storage by maintaining better physiological activities and enhancing the absorption of water

Cut peony (Paeonia lactiflora Pall.) has a very short and poor-quality vase life after long-term cold storage. A basic vase solution of 0.5% sucrose and 0.5 mM melatonin was first screened in deionized water, and it prolonged the vase life of peony ‘Sarah’ from 4.7 d to 6.7 d after 30 d of cold storage at 2–3 °C. A response surface analysis was then used to design a composite vase solution (CVS) by adding 1690 mg L−1 NaCl, 129 mg L−1 citric acid and 68 mg L−1 6-benzyladenine to the basic vase solution, which further prolonged the vase life from 7.5 to 8.9 d in three independent tests. This was accompanied by an increase in the diameters of flowers and the uptake of water by the petals. The membrane permeability and antioxidant capacity in petals were further analyzed and showed that CVS effectively alleviated the damage to cell membranes and enhanced the antioxidant capacity, which ensured cell integrity. Thus, this maintained the physiological activities of the flowers during vase period. The inducing of PlPIP1;3 by CVS may help to enhance the absorption of water by cells, whereas PlTIP1;1 may play a major role in maintaining vase quality in its later stages. Significant inhibition of PlSAG39-like by CVS also confirmed its function of delaying senescence. Finally, widespread testing of the CVS indicated that it was more suitable for double-petal peonies. These results may provide more options to improve the postharvest quality of cut peonies after long-term cold storage.