When excised Chinese cabbage (Brassica campestris ssp. pekinensis Rupr. cv. Kungjung) leaves were floated on buffer solution containing 10 mM polyamines, chlorophyll loss was retarded under the dark condition, while chlorophyll retention was not affected under the light. Spermine was more effective than any others in chlorophyll retention of excised leaves. A diamine, cadaverine was the most effective in preventing protein degradation for 30 hr in the dark, while spermidine, spermine, and kinetin promoted protein degradation. In the light, protein retention was not affected by polyamine treatment. Protein degradation of detached leaves was increased by polyamine treatment to a greater extent in the light than in the dark.
Peroxidase activity in detached leaves increased as they were aging. Polyamine reduced peroxidase activity more than 50% in the dark, as compared with aging control. The effects of exogenous polyamine applications on Chinese cabbage leaves were similar to those of exogenous kinetin treatment. A negative correlation was obtained between chlorophyll content and peroxidase activity (r = -0.4152, n = 19).
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