Callus browning is a significant problem that hinders plant tissue regeneration in Paeonia ostii “Fengdan” by causing cell death and inhibiting growth. However, the molecular mechanism underlying callus browning in P. ostii remains unclear. In this study, we investigated the metabolites and potential regulatory genes involved in callus browning of P. ostii using metabolomic and transcriptomic analyses. We found a significant accumulation of phenolic compounds in the browned callus, represented by flavonoid compounds. Notably, the accumulations of luteotin and disomentin were higher in browning calli compared to non-browning calli. Transcriptomic analysis identified that candidate genes associated with flavonoid biosynthesis, including flavonoid 3-hydroxylase (PoF3H) and flavone synthase II (PoFNSII), were highly expressed in the browned callus of P. ostii “Fengdan”. Weighted gene co-expression network analysis (WGCNA) further highlighted that polyphenol oxidase (PoPPO) which encoded polyphenol oxidase, together with flavonoid biosynthesis-related genes such as flavanone 3-hydroxylase (PoF3H) and flavonone Synthase II (PoFNSII), as well as cellular totipotency-related genes wuschel-related homeobox 4 (PoWOX4), were involved in callus browning. Based on these findings, we proposed the molecular mechanism by which flavonoid accumulation, polyphenol oxidation, and cellular totipotency pathways contribute to callus browning in P. ostii. Our study provides new insights into the molecular mechanism underlying callus browning and offers the foundations to facilitate the establishment of an efficient plant tissue regeneration system in P. ostii.

Tropical ornamental Anthurium andraeanum requires substantial electrical heating for overwintering when cultivated in greenhouses in subtropical regions, making cold tolerance improvement a key factor for cost reduction. However, whether exogenous 6-Benzylaminopurine (6-BA) can enhance cold hardiness in Anthurium and its underlying mechanisms remain unclear. In this study, we conducted a controlled experiment to compare the physiological and biochemical responses of A. andraeanum ‘Alabama’ subjected to low-temperature stress following foliar application of 6-BA versus water. Our results show that, compared with water treatment, 6-BA application was associated with better preservation of subcellular structural integrity, higher proline accumulation, lower hydrogen peroxide content, decreased relative electrical conductivity, increased leaf fresh weight, dry weight, and area along with reduced water content, and lower stomatal density. These findings suggest that, under defined low-temperature conditions, 6-BA is associated with enhanced physiological performance in A. andraeanum, potentially through coordinated effects on subcellular stability, osmotic adjustment, reactive oxygen species accumulation, leaf morphology and water metabolism, and stomatal density. This work provides a theoretical basis and technical reference for cold-tolerant cultivation of Anthurium.