Study On Cold Tolerance Of Flower Organ Of Cut Chrysanthemum In Winter

Chrysanthemum was one of the four cut flowers in world, was also very important in China for cutting flower recent years. Winter chrysanthemum was one special population and more cold tolerance. The relative electric conductivity (REC), content of MDA, soluble sugar and protein, SOD,POD activity and pollen viability under natural and artificial low temperature were investigated in four winter cut chrysanthemum cultivars'Hanzi', 'Hanhuang'. The logistic equation was constructed based on the relationship between REC and temperature below 0℃, then the semi-lethal temper- ature(LT50) was determined, and then compared the cold tolerance of different cultivars, different florets and different flowering by variance analysis. The main results were as follows:(1) From 15th Dec to 27th,2008, the tendency of REC, MDA content of four cultivars changed reversely compared with the temperature, while SOD,POD and content of soluble protein were highly related to the low temperature, and the soluble sugar content accumulated all the time. The four different cultivars improved the cold tolerance by regulating the activity of SOD and the contents of soluble sugar and protein.(2) The LT50 in different florets and flowering of'Hanzi'and'Hanhuang'ranged from-8.82℃～-12.94℃. When temperature from CK (14.4～16.2℃.) to 3℃, the SOD activity, soluble protein and pollen viability increased at beginning and then decreased, while MDA changed reversely, and the soluble sugar content accumulated all the time. The change appeared at 9℃to/or 6℃, and the temperature were critical temperature point of physiological barrier.The greatest germination capacity of 'Hanzi' and 'Hanhuang' appears when temperature was 12℃and 9℃, respectively. All of these showed that the pollen viability of 'Hanzi'was more easily affected by low temperature.(3) The changed of physiological and biochemical indexes suggested that the chilling tolerance of two chrysanthemum was'Hanhuang','Hanzi', in turn. Tubular florets were more cold tolerant than ray florets, initial flowering was also stronger than that of full flowering.The results of artificial low temperature treatment were consistent with natural low temperature.(4) The REC, LT50, MDA, SOD, soluble sugar and pollen viability were closely related to cold hardiness of winter chrysanthemum. As natural temperature changed, no significant correlation between soluble protein and cold resistance were observed, while soluble protein was closely with cold tolerance by artificial temperature dropping. POD was not a good index for cold hardiness in chrysanthemum.