Rapid wilting after harvest greatly decreases the ornamental and economic value of fresh-cut flowers. To determine how chlorine dioxide (ClO₂) affects postharvest flower quality, Paeonia lactiflora ‘Hushui Dangxia’ cut flowers in bottles were treated with different concentrations of ClO₂ (0, 25, 50, 75, and 100 mg L⁻¹). Among the treatments, ClO₂ 75 (i.e., 75 mg L⁻¹) decreased the bacterial growth and lignin content at the P. lactiflora flower stem base, while also decreasing the degree of flower stem vessel blockage. Additionally, the ClO₂ 75 treatment increased the relative fresh weight, water balance, soluble sugar content, soluble protein content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase), but decreased the malondialdehyde content and ethylene release rate of P. lactiflora cut flowers. Thus, the aging of P. lactiflora flowers was delayed, thereby maintaining the cut flower quality. Furthermore, the vase life (i.e., ornamental period) increased by three days.

SERK is a marker gene for early somatic embryogenesis. We screened and functionally verified a SERK-interacting protein to gain insights into tree-peony somatic embryogenesis. Using PoSERK as bait, we identified PorbcL (i.e., the large subunit of Rubisco) as a SERK-interacting protein from a yeast two-hybrid (Y2H) library of cDNA from developing tree-peony somatic embryos. The interaction between PorbcL and PoSERK was verified by Y2H and bimolecular fluorescence complementation analyses. PorbcL encodes a 586-amino-acid acidic non-secreted hydrophobic non-transmembrane protein that is mainly localized in the chloroplast and plasma membrane. PorbcL was highly expressed in tree-peony roots and flowers and was up-regulated during zygotic embryo development. PorbcL overexpression caused the up-regulation of PoSERK (encoding somatic embryogenesis receptor-like kinase), PoAGL15 (encoding agamous-like 15), and PoGPT1 (encoding glucose-6-phosphate translocator), while it caused the down-regulation of PoLEC1 (encoding leafy cotyledon 1) in tree-peony callus. PorbcL overexpression led to increased indole-3-acetic acid (IAA) content but decreasing contents of abscisic acid (ABA) and 6-benzyladenosine (BAPR). The changes in gene expression, high IAA levels, and increased ratio of IAA to ABA, BAPR, 1-Aminocyclopropanecarboxylic acid (ACC), 5-Deoxystrigol (5DS), and brassinolide (BL) promoted embryogenesis. These results provide a foundation for establishing a tree-peony embryogenic callus system.