Effects of cold acclimation on cold resistance of chrysanthemum varieties

【Objective】 To clarify the positive effects of cold acclimation on chrysanthemum cold resistance, so as to provide a theoretical reference for further research on chrysanthemum cold resistance and further exploration of chrysanthemum cold resistance quality.【Method】 Two chrysanthemum varieties, Chazi Yanhong and Jinlong Tengyun, were used as test materials. Cold treatment(24 h at -4℃) and cold acclimation treatment(cold acclimation for 24 h at 4℃ and then 24 h at -4℃) were set and normal temperature(25℃) was taken as the control to determine the changes of physiological indexes such as chlorophyll content, antioxidant enzyme activity, relative conductivity(REC), malondialdehyde(MDA), proline(Pro), active oxygen and to analyze the correlation of various physiological indexes. Membership function method was used to comprehensively evaluate cold tolerance of the two chrysanthemum varieties.【Result】 After cold acclimation and cold treatment, the chlorophyll content and antioxidant enzyme activity of chrysanthemum leaves of the two chrysanthemum varieties decreased gradually, but REC, MDA and Pro content of the leaves gradually increased. Peroxidase (POD) activity, REC, content of MDA, Pro, hydrogen peroxide (H₂O₂) and superoxide anion (O₂^-) in the leaves of the two varieties in the cold acclimation treatment group were significantly lower than those in the cold treatment group(P<0.05, the same below). POD activity, REC, Pro and O₂^- content changed significantly in Jinlong Tengyun variety, while MDA and H₂O₂ content in the Chazi Yanhong variety significantly decreased. Chlorophyll content and POD activity in cold acclimation treatment group were significantly higher than those in cold treatment group. Content of chlorophyll a, chlorophyll b and POD activity of Jinlong Tengyun variety increased by 38%, 54% and 18% respectively compared with those in cold treatment group. Carotenoid content doubled in the Chazi Yanhong variety compared with that in cold treatment group. The correlation ana-lysis showed that the cold tolerance of Jinlong Tengyun was greater than that of Chazi Yanhong. Without cold acclimation, the cold tolerance of Jinlong Tengyun was better than that under cold acclimation, while the cold tolerance of Chazi Yanhong was worse than that under cold acclimation.【Conclusion】 After cold acclimation, the physiological characteristics of the two varieties are better than those before cold acclimation, and Jinlong Tengyun has better cold tolerance than Chazi Yanhong, which indicates that cold acclimation could protect chrysanthemum to a certain extent, reduce the degree of damage caused to the plasma membrane of chrysanthemum cells, thus improving cold resistance of chrysanthemum.