Paclobutrazol leads to enhanced antioxidative protection of sweetpotato under flooding stress

The aim of this research was to study the effect of paclobutrazol pretreatment on the changes of antioxidative enzymes and antioxidants in the flooding-stressed sweetpotato Ipomoea batatas (L.) Lam. 'Tainung 57' was grown in plastic boxes in a screenhouse and maintained in optimal water conditions for 45 days followed by PBZ treatments (0 and 0.5 mg/plant) for 1 day. Then flooding was induced by raising the water level to 5 cm above the soil medium surface for a 5-day period followed by drainage for 2 days. A factorial experiment in randomized complete blocks with three replications was conducted. Young fully expanded leaves from each plant were clipped to measure enzyme activities and antioxidant contents. Increased ascorbate peroxidase activity, total glutathione, oxidized ascorbic acid, and total ascorbic acid amounts on different days of flooding provided the sweetpotato with increased flooding tolerance. The levels of glutathione reductase, ascorbate peroxidase, total glutathione, oxidized ascorbic acid, and malondialdehyde were regulated and elevated by paclobutrazol pretreatment under non-flooded conditions. Paclobutrazol pretreatment increased the levels of all antioxidative enzymes and antioxidants following different flooding durations and drainage, and boosted the flooding tolerance of the sweetpotato.