Antioxidant Metabolism During Cold Acclimation In Two Zoysiagrass Cultivars Contrasting In Freezing Tolerance.

A large variation exists in freezing tolerance between zoysiagrass species and between cultivars within same species, physiological mechanisms of zoysiagrass tolerance have not been well documented.  This study was to investigate the change in antioxidant metabolism during cold acclimation (CA) in ‘Meyer’ (cold tolerant cultivar) and ‘Cavalier’ (cold sensitive cultivars) associated with freezing tolerance under controlled environments. The two cultivars were subjected to 8/4 C (day/night) and photosynthetic active radiation at 250 umol m^-2 s^-1 (10-h photoperiod) for 3 weeks. The activities of selected antioxidant enzymes were analyzed weekly during CA. Superoxide dismutase activity increased and catalase activity declined during CA. There was no change in ascorbate peroxidase activity during CA. Superoxide dismutase activity was higher in Meyer than Cavalier as measured at the end of CA. Reactive oxygen species and abscisic acid were involved in triggering antioxidant defense response during CA.  The results suggest that zoysiagrass species/cultivars with higher antioxidant enzyme activity during CA may have greater freezing tolerance and winter survival.