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Degradation of chlorophyll in spinach (Spinacia olearacea L. cv. Hybrid 612) appeared to be regulated through the peroxidase-hydrogen peroxide pathway, which opens the porphyrin ring, thus resulting in a colorless compound. This conclusion was arrived at from the analysis of chlorophylls (Chls) and their metabolizes by HPLC and of enzyme activities catalyzing the degradative reactions. Chls decreased at 25C but not at 1C. The chlorophyll oxidase pathway was not active, as noted by the lack of accumulation of a reaction product named Chl a-1. Lipid peroxidation increased with storage, but the products of the reaction. did not degrade chlorophyll, as noted by the lack of increase in Chl a-1. Chlorophyllase activity increased, but chlorophyllide, the expected product of the reaction, changed minimally during senescence. Ethylene at 10 ppm did not alter the pathway that degraded chlorophyll in spinach.

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22 UV-B irradiation was applied to broccoli florets to investigate its effect on 23 chlorophyll degradation and chlorophyll-degrading enzyme activities in stored broccoli. 24Broccoli florets were irradiated with UV-B doses at 4.4, 8.8 and 13.1 kJ m -2 and then 25 kept at 15 ºC in darkness. We found that a UV-B dose of at least 8.8 kJ m -2 efficiently 26 delayed the decrease of the hue angle value and the contents of chlorophylls a and b. 27Chlorophyllide a and 13 2 -hydroxychlorohyll a gradually decreased with senescence. 28Pheophorbide a and pyropheophorbide a levels were significantly higher in broccoli 29 without UV-B treatment. Chlorophyllase and chlorophyll-degrading peroxidase activities 30 with UV-B treatment were suppressed, as well as the activity of Mg-dechelatase. Mg-31 dechelating substance activity was also suppressed with this treatment. We concluded 32 that UV-B treatment effectively suppressed chlorophyll degradation in broccoli florets 33 during storage, suggesting that the effect could be due to the suppression of chlorophyll-34 degrading enzyme activities.