Research On The Physiological Response To Cold Stress And Exogenuous Hormones Of Zoysia Japonica

Zoysiagrass, a warm-season turfgrass species, experiences freezing damage in many regions, the mechanisms of its cold acclimation and freezing tolerance have not been well understood. This study was designed to investigate changes in metabolites (carbohydrate, proline, proteins), and antioxidant enzyme activity during cold acclimation(21d). Meanwhile, this study investigates the signal molecule (ABA and H2O2) and related MDA and antioxidant enzyme activity changes in the first period of cold acclimation (3d). Finally,3groups of different concentration of exogenous ABA and H2O2were sprayed on the I eaf of Zoysi a japonica cultivar Chi nese Common to study thei r effects on cold tolerance as water as CK. Two zoysiagrass cultivars (Chinese Common (cold tolerant) and Lanyin-3(relatively cold sensitive) were choose as materials. The objective of this study is to provide theoretic physiology reference of Zoysiagrass in cold acclimation, to provide certain guidance of resistant cultivars breeding and management improvement. The result showed that:1、The LT50of Chi nese Common and Lanyin-3are-12.5℃癈and-9℃respectively.2、The I eaf soluble sugar, starch, proline, and soluble protein content increased in response to cold acclimation. The leaf superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activity tended to decline from0to7d and then increased from7to14d during cold acclimation.3、Common accumulated more metabolites (soluble sugars, starch, proline) and had higher SOD activity relative to Lanyin during cold acclimation.4、As to the first period of cold acclimation, the leaf hydrogen peroxide (H2O2) and and related MDA and antioxidant enzyme activity increased rapidly in response to cold acclimation while leaf ABA remain steady.5、High concentration of ABA and H2O2could decline the winter survival of Zoysiajaponica while low and middle level of concentration of ABA and H2O2could help to improve it. The effects of improving Chinese Common from the best to the worse is as following:ABA100mmol/L> ABA50mmol/L> H2O2100mmol/L> H2O250mmol/L> H2O215mmol/L> ABA150mmol/L In conclusion, the results suggest that the zoysiagrass cultivar with higher levels of carbohydrate, praline content, and SOD activity during cold acclimation period may have a greater winter survival than those with lower levels of carbohydrate and prolineand SOD activity. Moreover, H2O2may serve as signal for inducing antioxidant responses. Both of exogenousABA and H2O2have effects on the cold tolerance of zoysiagrass： low concentration of ABA and H2O2can help to improve the cold tolerance of zoysiagrasswhile high concentration ABA and H2O2help to deteriorate cold tolerance.