Abstract:

The relative electric conductivity（REC） was determined in the leaf of emergent rhizomes of chrysanthemum during the natural drop in temperature from autumn to winter. The logistic equation was constructed based on the relationship between REC and temperature, then the semi-lethal temperature was determined. The cold tolerance of 8 cultivars was evaluated by LT₅₀. The validity of LT₅₀ in evaluating the cold tolerance of chrysanthemum was proved by recovery of emergent rhizome test. The results showed that the LT₅₀ temperature decreased with the drop in temperature, the decrease of LT50 is cultivar dependent, the decrease of LT₅₀ varied from 4.0℃ to 9.4℃.The cold tolerance of 8 cultivars decreased in the order of 'Jinling Huanghe' ,'Yinxing' ,'Aoyun Wanxia' ,'Jinling Zhiguang' , 'Aoyun Jinyun' , '03（6）-16', '03（6）-12' and 'Aoyun Huoju'. No significant correlation between cold tolerance and florescence was observed. Emergent rhizomes recovering test is overall in consistence with the result of the freezing test indicating that LT50 temperature was a credible indicator to evaluate the cold tolerance of chrysanthemum. No emergent rhizomes recovered when the lethal low temperature was below -14℃.

Key words: Dendranthema×grandiflorum, Cold tolerance, Semi-lethal temperature（LT₅₀）, Relative electric conductivity