Postharvest Calcium Propionate Treatment Promotes Wound Healing in Carrot Taproots by Enhancing Phenylpropanoid Metabolism and Reactive Oxygen Species Levels

To investigate the effect of postharvest calcium propionate treatment on wound healing of carrot taproots and to explore the underlying mechanism from the perspectives of phenylpropanoid metabolism and reactive oxygen species (ROS) metabolism.

Artificially wounded carrot taproots were dipped in 36 mmol/L calcium propionate, and the healing efficacy was evaluated by observing the deposition of suberin polyphenolics (SPP) and lignin at wound sites and by measuring the firmness of healing tissues and mass loss in wounded carrot taproots. The activities of key enzymes involved in phenylpropanoid metabolism, the gene expression of transcription factors, the contents of secondary metabolites, the activities of key enzymes related to ROS production, and H₂O₂ content were analyzed.

Calcium propionate treatment accelerated the accumulation of SPP and lignin at wound sites during healing, increased the firmness of healing tissues, and reduced mass loss in the taproots. The treatment also significantly upregulated the expression of the transcription factor genes DcCML3 and DcCAMTA3, activated phenylalanine ammonia-lyase, and increased the contents of total phenolics and flavonoids. Furthermore, calcium propionate treatment enhanced the activities of NADPH oxidase and superoxide dismutase (SOD), along with H₂O₂ content, at wound sites throughout the healing period. It also increased superoxide anion radical levels during the early healing stage and boosted peroxidase (POD) activity.

Calcium propionate treatment accelerated wound healing by increasing ROS levels and enhancing POD activity through the up-regulation of DcCML3 and DcCAMTA3.