Effect of Exogenous Sugars on Active Oxygen Balance of Cut Freesia Flowers

Taking cut flowers of Freesia hybrid ‘Shangnong Jinhuanghou'as material,being immersed in 6% glucose solution(treatment group)and distilled water(control),respectively,the changes of antioxidant enzyme activity and membrane lipid peroxidation level in petals during vase holding were studied.The results showed that the vase life of a whole inflorescence was about 10d,while an individual floret was less than one week.Water absorption content in petals changed obviously during the vase holding,with a decrease in the early stage and picking up after 7d.Soluble protein content in control showed a trend of gradual decline,while a peak was observed at 4din treatment group followed by a constant decrease up to the end of vase holding.Superoxide dismutase(SOD)and catalase(CAT)activities had a consistent trend,rising early and then decreasing during the vase holding.However,peroxidase(POD)activity presented a constant increase trend.Meanwhile,a significant difference in POD activity was observed at different position of freesia inflorescence,the highest activity and the lowest activity presented in base floret and upper floret at the same vase time,respectively.The content of Malondialdehyde(MDA)accumulated gradually during vase holding,and the higher MDA content was observed in base floret than that in middle floret and upper floret at the same vase time,respectively.The content of super oxygen free radicals(O·2)increased obviously at 2dfollowed by a drop at 4d,and then increased up to the end of vase holding.Change trend of treatment group was consist with control,but O·2content was varied in different periods and disparate positions of the inflorescence.The results revealed that the water loss,decreased activity of antioxidant enzymes,the accumulation of O·2and the rising of membrane lipid peroxidation level were considered to be the main causes of senescence of cut Freesiaflowers.