Objective  Physiology and biochemistry associated with the flower bud differentiation of Narcissus tazetta var. chinensis suppressed by low temperature were studied.

  Method   Three-year-old Chinese narcissus bulbs were stored under 15 ℃ or room temperature to compare the differences on the protective enzyme activity and soluble protein and carbohydrate contents in the scales.

  Results  Under room temperature, the contents of superoxide anion (O₂·⁻) and hydrogen peroxide (H₂O₂) in the scales rose initially followed by a decline and another rise; the activity of superoxide dismutase (SOD) remained high, peroxidase (POD) low, and catalase (CAT) ascended significantly in late stage; and, during the floret primordium developmental stage, the contents of sucrose and starch in scale declined, while α-amylase and soluble sugar stayed high. In contrast to room temperature, at 15 ℃ the O₂·⁻ and H₂O₂ in the scales increased but the SOD activity was not affected, while the POD and CAT activities in the stamen primordium significantly increased and the contents of soluble sugar, sucrose, and starch as well as the activity of α-amylase lowered at different sampling points.

  Conclusion  The accumulation of carbohydrates, such as soluble sugars and starch, in narcissus scales was greatly affected by the low storage temperature at 15 ℃. It was crucial for the Chinese narcissus flower bud differentiation, particularly during the development of floret primordium.