Can H₂O₂ application reduce chilling injury of horticultural crops?

Endogenous hydrogen peroxide (H₂O₂) at low concentration is a signaling compound leading to adaptation and stress tolerance during plant abiotic stress. At high concentrations, H₂O₂ can lead to cell death. Our study was to examine whether exogenous application of H₂O₂ could lead to stress tolerance and thereby improve the quality of sweet potato (Ipomoea babatas) and sweet peppers (Capsicum annuum). This study consisted of two types of experiments: chilling injury in sweet potato (growth chamber) and storage quality in sweet peppers (greenhouse). In sweet potato (model plants), excised leaves had less chilling injury, when stored at 2.5°C for 2 to 3 days, if the petioles were immersed in 15 mM H₂O₂ as compared to de-ionized water (control). When cv. Purple (PUR) sweet potato shoots were subjected to 3-day chilling at 2.5°C, a 48 h pre-treatment of 150 mM H₂O₂ under 16 h photoperiod reduced chilling injury, but H₂O₂ showed no effect under 8 h photoperiod. In sweet peppers (greenhouse crop), shelf life after 4-week storage was longer when 500 ppm H₂O₂ was administered through the hydroponics system prior to fruit harvest and storage. Decline in the beneficial effect on shelf life was observed through pulsed H₂O₂: shelf life was increased if sweet peppers were harvested one or two weeks after H₂O₂ application, but such benefit was not observed after three weeks. Our data seem to support the possibility that exogenous H₂O₂ may lead to chilling tolerance. Our preliminary data also illustrated that the benefits of exogenous H₂O₂ application could not always be observed under all experimental conditions (as main effect). Rather, H₂O₂ effects were often observed under specific combinations of conditions (as interactions), demonstrated by photoperiod in sweet potato or specific number of weeks elapsed between H₂O₂ application and harvest in pepper fruits. Therefore further studies are always required to devise specific, practical H₂O₂ applications for any targeted benefits in crop production.