Evaluation of physiological changes in sweetpotato (Ipomoea batatas) tuberous root under normoxia high-CO2 conditions

Sweetpotato tuberous roots (SPTRs) often suffer from high-CO2 injury during storage. This research explored the epidermal stomatal movement and physiological characteristics of SPTRs stored in air or normoxic high CO2 (NHC) for 10 d at 25 °C. The results showed that NHC induced the epidermal stomatal closure of SPTRs leading to high ethanol and abscisic acid glucose ester (ABA-GE) contents, inner tissue browning, but slight changes in the physiological metabolism and quality of the control root. Transcriptome analysis showed that NHC increased the transcript abundance of the UGT gene related to ABA-GE accumulation. NHC activated gene expression of CA and upregulated the gene expression of the stomata ABA-signaling pathway (PP2C, SnRK2.3, and SLAC1). NHC also upregulated the expressions of ethanol metabolism (PDC and ADH), internal browning (LAC and C4H), and alternative respiratory pathway (AOX)-related genes. High-CO2 injury is speculated to be a hypoxia response caused by the stomatal closure of SPTRs.