Exogenous H2O2 improves the chilling tolerance of manilagrass and mascarenegrass by activating the antioxidative system

The effect of foliar pretreatment by hydrogen peroxide (H2O2) at low concentrations of 0, 5, 10, and 15 mM on the chilling tolerance of two Zoysia cultivars, manilagrass (Zoysia matrella) and mascarenegrass (Zoysia tenuifolia), was studied. The optimal concentration for H2O2 pretreatment was 10 mM, as demonstrated by the lowest malondialdehyde (MDA) content and electrolyte leakage (EL) levels and higher protein content under chilling stress (7A degrees C/2A degrees C, day/night). Prior to initiation of chilling, exogenous 10 mM H2O2 significantly increased catalase (CAT), ascorbate peroxidase (APX), glutathione-dependent peroxidases (GPX), and glutathione-S-transferase (GST) activities in manilagrass, and guaiacol peroxidase (POD), APX, and glutathione reductase (GR) activities in mascarenegrass, suggesting that H2O2 may act as a signaling molecule, inducing protective metabolic responses against further oxidative damage due to chilling. Under further stress, optimal pretreatments alleviated the increase of H2O2 level and the decrease of turfgrass quality, and improved CAT, POD, APX, GR, and GPX activities, with especially significant enhancement of APX and GPX activities from the initiation to end of chilling. These antioxidative enzymes were likely the important factors for acquisition of tolerance to chilling stress in the two Zoysia cultivars. Our results showed that pretreatment with H2O2 at appropriate concentration may improve the tolerance of warm-season Zoysia grasses to chilling stress, and that manilagrass had better tolerance to chilling, as evaluated by lower MDA and EL, and better turfgrass quality, regardless of the pretreatment applied.