Effect and Possible Mechanism of Postharvest Pre-storage Temperature on Wound Healing of Potato Minitubers Grown in Aeroponic System

The effect of postharvest pre-storage temperature on the wound healing of potato minitubers grown in an aeroponic system was evaluated, and its possible mechanisms were also explored. Potato mini-tubers (cv. Tongshu 1’) free from artificial damage were pre-stored at 4, 15 or 25 ℃ (86%–88% relative humidity) in a dark environment for 20 days. Mass loss rate was measured during pre-storage, the accumulation of suberin and cork in periderm cells was observed, the degree of suberization was examined, and the changes in phenylpropane and reactive oxygen species metabolism in potato tuber periderm were also analyzed. Results showed that pre-storage at 15 ℃ significantly promoted the accumulation of suberin polyphenolics (SPP) and suberin polyaliphatics (SPA) and the degree of suberization in periderm tissue. On the fifth day of pre-storage, the accumulation of SPP and SPA and the degree of suberization in potato tubers prestored at 15 ℃ were higher than those at 4 and 25 ℃ by 50.90% and 26.94% (P < 0.05); 44.89% and 30.23% (P < 0.05); and 27.66% and 8.18%(P < 0.05), respectively. Pre-storage at 15 ℃ also significantly increased phenylalanine ammonia lyase (PAL) activity (P < 0.05), and augmented the contents of total phenols, flavonoids and lignin. On day 5, PAL activity in potato tubers prestored at 15 ℃ was 34.46% and 12.64% higher than that at 4 and 25 ℃, respectively (P < 0.05). The contents of total phenols and flavonoids were 11.93% and 40.05% higher than those at 4 ℃, and 2.72% and 15.50% higher than those at 25 ℃, respectively. On the 20^th day, the content of lignin in potato tubers prestored at 15 ℃ was 24.50% and 8.24% higher than that at 4 and 25 ℃, respectively (P < 0.05). In addition, pre-storage at 15 ℃ significantly increased the contents of H₂O₂ and superoxide anion and peroxidase (POD) activity in periderm tissue. The findings suggested that postharvest pre-storage at 15 ℃ can accelerate the wound healing of potato minitubers grown in an aeroponic system through activating phenylpropane and reactive oxygen species metabolism in periderm tissue, and increasing the accumulation of SPP and SPA and the degree of suberization.